Document text
MHI
MHI·
FM 5-15
Copy 3
DEPARTMENT
OF THE ARMY FIELD
MANUAL
FIELD
FORTIFICATIONS
HEADQUARTERS,
DEPARTMENT
OF
THE
ARMY
AUGUST 1968
TAGO 20013A
*FM 5-15
FIELD MANUAL
HEADQUARTERS
DEPARTMENT OF THE ARMY
No. 5-15
WASHINGTON, D.C., 9 August 1968
FIELD FORTIFICATIONS
Pargsraph
Page
CHAPTER
1.
GENERAL
Section I. Introduction -..
-----------------------
1-1,1-2
1-1
II.
Basic considerations -..
-----------------
1-3-1-8
1-1
CHAPTER
2.
PERSONNEL AND EQUIPMENT
PROTECTIVE MEANS
Section I. Principles and methods ..-------------------
2-1-2-3
2-1
II.
Individual emplacements .-.----------------
2-4, 2-5
2-3
III.
Crew-served infantry weapons
emplacements
2-6--2-10
2-9
IV.
Vehicle and artillery emplacements .
.--------
2-11-2-14
2-12
V.
Aircraft revetments ------------------------- 2-15, 2-16
2-19
CHAPTER
3.
SHELTERS
Section I.
Hasty shelters ..........--------------.
3-1--3-4
3-1
II.
Deliberate shelters ..--.---------------
-
35--3-12
3-6
CHAPTER
4.
TRENCHES AND FIELDWORKS
Section I. Trenches----------------------------------
4-1--4-6
4-1
II.
Fieldworks ----------------------------------
4-7-4-12
4-14
CHAPTER
5.
OBSTACLE EMPLOYMENT
Section I.
Principles
....-..
-----------------
5-1, 5-2
5-1
II.
Artificial land obstacles -.......
.----
5-3--6-8
5-4
III.
Beach and river line obstacles -....
........
5-9-5-12
5-7
CHAPTER
6.
BARBED WIRE ENTANGLEMENTS
Section I.
Materials .....-.....---.
-------
6-1,6-5
6-1
II.
Construction procedures ----------------------
6-6-6-16
6-9
III.
Material and labor estimates -----------------
6-17, 6-18
6-23
CHAPTER
7. ANTIVEHICULAR OBSTACLES .-..
.
......
7-1-7-11
7-1
8.
BEACH AND RIVER LINE OBSTACLES -.--
8-1-8-6
8-1
APPENDIX A.
REFERENCES -.-------------
-- --
- ----
A-1
B.
CONVERSION FACTORS-ENGLISH-
METRIC SYSTEMS -...
.........-
--- ---
B-1
C.
FORTIFICATION PROTECTION FACTORS
-
-....---
C-1
D.
USE OF EXPLOSIVES IN EXCAVATION
OF EMPLACEMENTS .-...
--- ---
D-1
INDEX -
..-..-..-...--
--.
------
--------
Index-1
'This manul wuprsedes FM 5-15, 26 Febnvry 1965.
TAGO 20018A
FM 5-15
CHAPTER 1
GENERAL
Section I. INTRODUCTION
1-1. Purpose
gether with devices and equipment under de-
This manual is a training guide for small units
velopment which may be available in the near
in the construction of field fortifications, in-
future are illustrated and discussed.
cluding protected firing positions for weapons,
c. Application. The material contained here-
personnel shelters, and defensive obstacles.
in is applicable without modification to both
nuclear and nonnuclear warfare.
1-2. Scope
d. Changes. Users of this manual are encour-
a. Fortifications. Detailed information on
aged to submit recommended changes or com-
the construction and progressive development
ments to improve the manual. Comments should
of emplacements, intrenchments, shelters, en-
be keyed to the specific page, paragraph, and
tanglements, and obstacles under varied cli-
line of the text in which the change is recom-
matic conditions is included in the manual.
mended. Reasons should be provided for each
The types of fortifications illustrated and dis-
comment to insure understanding and cornm-
cussed are generally within the capabilities of
plete evaluation. Comments should be for-
unskilled personnel. Standard plans, bills of
warded direct to the Commandant, U.S. Army
material, construction procedures, and esti-
Engineer School, Fort Belvoir, Va. 22060.
mated time and labor requirements are furn-
e. Metric Measures. Dimensions and dis-
ished.
tances are generally given in centimeters and
b. Tools and Equipment. Tools and equip-
meters. A conversion table to the English sys-
ment normally available to combat units to-
tem is furnished in appendix B.
Section II. BASIC CONSIDERATIONS
1-3. Use of Field Fortifications
emplacements and positions for personnel,
a. On the Offense. During offensive opera-
strengthening natural obstacles, installing ar-
tions periodic halts may be required to re-
tificial obstacles, and providing camouflage.
group,
resupply,
or
consolidate
positions
c. Fortification Plans. Plans for fortifica-
gained. Where the enemy threat is known to
tions not only provide for the desired degree
include a counterattack capability (or prob-
of protection but also for bringing the enemy
ability), offensive units should seek available
under the maximum volume of effective fire
cover or should dig hasty emplacements as
as early as possible. Fortification plans are
described in paragraph 2-4a.
usually based on progressive construction;
b. On the Defense. A defensive position is
that is, proceeding from open to covered em-
built around a series of organized and occupied
placements and shelters to the ultimate pro-
tactical positions. Positions are selected for
tection permissible under the circumstances.
their natural defensive strength and the ob-
Characteristics of personnel and individual
servation afforded. Fortification measures in-
weapons emplacements are shown in table 1-
clude clearing fields of fire, digging weapon
1 Located in Back of Manual
AGO 2001JA
1-1
FM 5-15
d. Dispersion. The separation of units and
c. Simplicity and Economy. The emplace-
individuals is a primary means of increasing
ment or shelter should be strong and simple,
protection, particularly from the effects of nu-
require as little digging as possible, and be
clear weapons. If the area occupied by a unit
constructed when
possible with materials
is doubled, it is less vulnerable to shell fire
that are immediately available.
or the effects of nuclear weapons. Proper dis-
d. Progressive Development. Plans for de-
persion can greatly reduce the requirements
fensive works should allow for progressive de-
for high level of protection from field fortifi-
velopment to improve the usefulness of the
cations. The amount that a unit spreads out
fortification. Development of fortification can
depends on the mission, terrain, and the en-
be accomplished in three steps--
emy situation. Fortifications, properly em-
(1) Digging in quickly where speed is the
ployed, can be used in lieu of or to supplement
principal consideration and no special tools or
dispersion, but fortifications are particularly
materials are required.
important for units that cannot disperse suf-
(2) Improvising with local materials.
ficiently to obtain adequate protection.
(3) Refining, using stock materials.
e. Alternate and Dummy Positions. When
e. Convealment. Fortifications should be
time and the situation permit, dummy and al-
built so that the completed work can be con-
ternate positions should be constructed to de-
cealed. It may not be practical to conceal a de-
ceive -the enemy and to allow flexibility in the
fensive position completely but it should be
defense.
concealed enough to prevent the enemy from
spotting the position by ground observation.
1-4. Responsibilities
If possible, dummy positions should be con-
Field fortifications are constructed by person-
structed at the same time as the actual posi-
nel of all arms and services. Hasty shelters
tions.
and emplacements are normally constructed by
f. Ingenuity. A high degree of imagination
the combat units occupying the position. Some
and ingenuity is essential to assure the best
engineer equipment and supervisory assist-
use of available materials as well as the best
ance are frequently required to assist the com-
choice and use of the fortifications constructed.
bat units. Fortifications of a more complex
character may require construction by engi-
1-6. Protection from Conventional Weapons
neer troops. Actually, engineers at all echelons
a. Digging In. Protection against conven-
of command assist in the preparation of plans
tional weapons is best provided by construct-
and orders and furnish technical advice and
ing a thickness of earth and other materials.
assistance in the construction of field fortifi-
This is done by digging into the ground so
cations.
that personnel and equipment offer the small-
est target possible to the line of sight of the
1-5. Basic Requirements for Fortifications
weapon. This means of protection is effective
a. Employment of Weapons. Emplacements
against direct fire of small arms and horizon-
must permit effective use of the weapons for
tally impelled shell fragments. Digging in also
which they are designed. This requirement may
provides some protection against artillery, in-
limit the protection which can be provided
fantry heavy weapons, bombs, and other aerial
and may influence the design and depth of
weapons. Advantage should be taken of all
adjacent shelters.
available natural cover. improvement of the
b. Protection. As far as possible, protection
position continues until the unit leaves the
should be provided against hazards except a
area.
direct hit or a close nuclear explosion. This
b. Overhead Cover. Overhead protection is
means that excavations should be as small as
important particularly in the forward areas
possible consistent with space requirements,
where the threat includes airburst shelling in
so as to obtain maximum protection from the
addition to the possibility of nuclear attack.
walls against airbursts and limit the effective
Covered firing positiops should be built for in-
target area for high trajectory weapons.
dividual riflemen. Small readily accessible
1-2
AGO 20013A
FM 5-15
shelters adjacent to weapons emplacements
presence of the nuclear threat does not ma-
are also necessary. A minimum of 15 to 20
terially alter the principles outlined above.
cm of logs, 45 cm (18 in.) sandbags, rock, and
a. Thermal Effect. Thermal radiation affects
dirt, in that order, is required for overhead
anything that will burn. The thermal effect
protection. Any available material may be used
may be reduced as a potential source of nu-
but cover should be kept low. However, cover
clear casualties by thermal shielding. Shield-
of this type will not protect personnel against
ing may be any opaque and noninflammable
direct shell hits. Overhead cover should be
material which shades the individual from the
strengthened and improved as long as the po-
source of heat. It is normally used as a cover
sition is occupied. Only part of the firing po-
over an excavation and it may be required for
sition should be covered. Sandbags are placed
shelter entrances or other openings. Personnel
over the logs to prevent dirt from falling on
should habitually wear
complete uniforms.
the occupants.
Hands, face, and neck should be covered. Pro-
tective clothing will also reduce casualties
1-7. Protection from Chemical and Biological
from burns.
Weapons
b. Blast. Blast can cause damage by its
Open or partially open emplacements afford
crushing effect. Blast from a nuclear explosion
no protection from chemical or biological at-
builds up against an obstruction, so vertical
tack. Personnel in open emplacements should
or near vertical faces should be avoided in
use the poncho for protection against liquid
earthworks above ground level.
contamination and the protective mask to pro-
c. Earth Shock. Collapse of earthworks, par-
vide protection from chemical vapors and bio-
ticularly unrevetted excavations, may result
logical aerosols. Overhead cover will delay
from the shock of nuclear explosions. To reduce
penetration of chemical vapors and biological
the risk from this effect, excavations deeper
aerosols, thereby providing additional mask-
than 1.4 meters (4 ft. 6 in.) should be revetted.
ing time and protection against direct liquid
For the same reason, overhead cover should
contamination. Covered
emplacements with
not normally exceed 45 cm (18 in.) unless
relatively small apertures and entrance areas
heavy roof supports are constructed.
which can be closed, provide protection from
d. Radiation. The effects of direct gamma
napalm and flamethrowers.
radiation can be reduced by keeping the ex-
posed openings of excavations and shelters as
1-8. Protection from Nuclear Weapons
small as possible and by increasing the thick-
Fortifications which are effective against mod-
ness of overhead protection for large shelters
ern conventional weapons are in varying meas-
to 75 cm (2 ft. 6 in.), supported by heavy roof
ure effective against nuclear weapons. The
timbers.
AGO 20013A
1-3
FM 5-15
CHAPTER 2
PERSONNEL AND EQUIPMENT PROTECTIVE MEANS
Section I. PRINCIPLES AND METHODS
2-1. Materials
a. Natural. Full use is made of all available
natural materials such as trees, logs, and brush
.
in constructing and camouflaging emplace-
CROWBAR
ments, shelters, and overhead cover. Usually,
enough natural material can be found to meet
the requirements for hasty or expedient forti-
fications. Snow and ice may be used in the
SPARE HAND
construction of emplacements and shelters in
MAUL
cold regions.
b. Other Materials.
(1)
Manufactured
materials,
such as
pickets, barbed wire, lumber, sandbags, cor-
rugated metal, and other materials for revet-
D HANDLED
CROSSCUT SAW
ting, camouflage, shelter, and concrete con-
SHOVEL
struction are supplied by support organiza-
tions.
(2) Captured enemy supplies, locally pro-
cured material, and demolished buildings are
PI
CK
MATTOCK
other sources of fortification construction ma-
HANDSAW
terials.
2-2. Methods of Excavating
a. Handtools. The individual soldier is equip-
ped with an intrenching tool and, if necessary,
he can use his helmet or bayonet to assist in
BOLT CUTTER
digging. Pick mattocks, shovels, or machetes
are also useful and frequently available for
this purpose. In addition, captured enemy
equipment may be available. The relative value
of each tool depends on the soil and terrain.
Figure 2-1. Intrenching eqnipment.
In arctic areas, a larger quantity of picks and
pick mattocks are required to aid in the prep-
more acements or shelters can be excavated
aration of emplacements in frozen ground. In-
ing machines,
backhoes, bulldozer,
buket
ing machines, backhoes, bulldozers, bucket
trenching equipment and engineer pioneer
trenching equipment and engineer pioneer
loaders, and scrapers may be used for larger
tools are illustrated in figures 2-1 and 2-2 re-
excavations and trenchmay be used for larger
spectively.
excavations and trenches where the situation
will permit the use of heavy equipment. Usual-
b. Equipment. Relatively narrow cuts with
ly, these machines cannot dig out the exact
steep or nearly vertical sides required for most
shape desired or will dig more earth than
AGO 20013A
2-1
FM 5-15
leaves, snow, or forest humus is removed care-
SHOVELS D
NAILS
fully from both the area to be excavated and
HANNDr
E ~ \/
from the ground on which excavated soil is to
B>/gRUSH '/
be placed. This material is used to cover the
LfONG
HOOK
WIRE
spoil when the work is completed. It is always
WE i
i ft
DGEaoer
using dummy field-works. Construction of
\ T / 47, ,
OPE
large weapons' emplacements in open country
AN
AX
having little or no natural cover can be'con-
cealed by camouflage nets suspended from
MATrOCKr
a7
/
stakes or trees before excavation is started.
The net should be suspended high enough above
-AACHEITE
ADZ
SLEDOGE MAU~L
*the
ground to permit excavation without snag-
HATCHET
ging by equipment or tools. When the excava-
Figure 2-2. Engineer pioneer tools.
tion is completed and the spoil covered with
sod or natural camouflage material, the net is
necessary, requiring completion of the excava-
lowered close to the ground so it is incon-
tion by hand. Additional revetment material
spicious from ground observation.
is usually required when machines are used.
b. Disposal of Soil. Usually excavated soil is
Distinctive scars on the ground resulting from
much lighter in color and tone than surface
the use of heavy equipment require more effort
soil and must be hidden carefully to prevent
for effective camouflage than fortification work
disclosure of the fortification (fig. 2-3). Soil
performed by hand.
may be disposed of by-
c. Explosives. Many fortification tasks are
(1) Using it to form a parapet if the top-
made easier and accomplished more quickly by
soil is carefully saved and used to cover the
using explosive in any type of soil. Special
parapet Turf, sod, leaves, or litter from under
explosive digging aids available include the
M2A3 and M3 shaped demolition charges,_
-.
the foxhole digging and explosive kit, and the
earth rod explosive kit set No. 1 (see TM 9-
1375-200). Details on the use of explosives for
fortifications and the explosive foxhole dig-
ger kit are given in appendix D.
2-3. Concealment and Deception
a. Methods. Concealment is of prime impor-
OIRT CONCEA
LED
tance in constructing defensive works. Con-
i
, T
cealment can be obtained by-
,,
(1) Careful siting, making maximum
use of background to break up outlines.
(2) Strict camouflage discipline through-
S-_
out all stages of construction, including rigid
A.
track discipline and carefully planned disposal
of soil.
(3) Intelligent use of natural and arti-
,
ficial camouflage materials. It may not be pos-
-
sible to conceal the position as a whole, but
-
usually it will be possible to prevent pinpoint-
-;(,
ing of individual works by ground observation.
-
DIRT REMOVED
Before any excavation is begun, all turf, sod;
Figure 2-4. Disposal of soil.
2-2
AGO 20013A
FM 5-1S
nearby bushes or trees are used to make the
(3) Collecting and using it, partly camou-
parapet resemble its surroundings.
flaged, to form parapets for dummy positions.
(2) Removing it and carefully hiding it
(4) Covering mixed snow and earth from
under trees or bushes or in ravines. Care must
excavated emplacements with a layer of fresh
be taken to avoid revealing tracks.
snow to camouflage them.
Section II. INDIVIDUAL EMPLACEMENTS
2-4. Types of Emplacements
offers immediate cover and concealment and
a. Hasty Emplacements. Hasty emplacements
can be quickly made into a hasty position (fig.
are dug by troops in contact with the enemy,
2-5). By digging the crater to a steep face on
when time and materials are limited. Hasty
the side toward the enemy, the occupant can
positions should be supplemented with over-
provide himself with a firing position. A small
head cover and strengthened as conditions per-
crater can later be developed into a foxhole.
mit. If the situation permits, the small unit
Craters, even if developed, are susceptible to
leader will verify the sectors of observation
being overrun by tracked vehicles.
and fire for the individual members of the squad
from their designated positions before they dig
individual foxholes. When the situation is sta-
bilized, even temporarily, positions are selected
-
-
->
-_
so they can be connected by trenches later.
The emplacements described below provide pro-
CRATER
tection against flat trajectory fire. They are
CROSS SECTION OF CRATER
ENEMY
used when there is no natural cover. Hasty
positions (fig. 2-4) are good for a short time
because they give some protection from direct
GROUN LINE
FOR PRONE (ELBOW RESTI
fire. If the unit remains in the area, they must
FOR KNEELING OR SITTING
be developed into well-prepared positions to
DOTTED
LINES INDICATE SPOIL TO REMOVE FOR
provide as much protection as possible.
IMPROVING
CRATER
Figure 2-5. Improved crater.
(2) Skirmisher's trench. This shallow pit
type emplacement (fig. 2-6) provides a tem-
porary open prone firing position for the indi-
vidual soldier. When immediate shelter from
-=.
Aheavy enemy fire is required and existing de-
filaded firing positions are not available, each
soldier lies prone or on his side, scrapes the
soil with his intrenching tool, and piles it in a
low parapet between himself and the enemy.
In this manner a shallow body-length pit can
be formed quickly in all but the hardest
ground. The trench should be oriented so that
it is least vulnerable to enfilade fire. A soldier
__r~F~
presents a low silhouette in this type of em-
placement and is protected to a limited extent
from small arms fire. It can be further devel-
oped into a foxhole or a prone emplacement.
Figure 2-4. Hasty positions in an open field.
(3) Prone emplacement. This emplacement
(1) Shell crater. A shell or bomb crater
(fig. 2-7) is a further refinement of the skirm-
of adequate size, 60 to 90 cm wide (2 to 3 ft),
isher's trench. The berm dimension of this em-
AGO 2001sA
2-3
FM 5-15
Figure 2-6. Skirmisher's trench.
placement, as shown in the parapet detail, is
varied to conform to the position and arm
cm
length of the occupant. It serves as a good
firing position for a rifleman and provides bet-
K
6'
ter protection against small arms or direct fire
t,
(APPROX)
weapons than the improved crater or skirm-
isher's trench.
I
socm
(4) Rocks, snow, and ice. Limited protec-
tion can be provided by piling up rocks, chunks
of ice, or packed snow. Icecrete, formed by
4cm
mixing dirt and water, is very effective as an
PARAPET DETAIL
arctic building material. A minimum of 30 cm
Figure 2-7. Prone emplacement.
of this material will resist penetration of small
arms fire.
must have at least 60 cm (2 ft.) of overhead
b. Foxholes. Foxholes are the individual
clearance if a tank overruns the foxhole. This
rifleman's basic defensive position. They afford
will normally provide protection against the
good protection against enemy small arms fire
crushing action of tanks; however, in loose
and can be developed from well chosen craters,
unstable soils it will be necessary to revet the
skirmishers' trenches, or prone emplacements.
walls of the foxhole in order to provide this pro-
Foxholes should be improved, as time and ma-
tection.
terials permit, by revetting the sides, adding
(b) Water sump. A water sump, 45 by
expedient cover, providing drainage, and exca-
60 cm (18 in. by 2 ft.) and 45 cm (18 in.) deep
vating a grenade sump to dispose of handgre-
below the fire step, is dug at one end of the
nades tossed into the hole by the enemy.
foxhole to collect water and to accommodate
(1) One-man foxhole. The overall dimen-
the feet of a seated occupant. One or two layers
sions and layout of the one-man foxhole are
of large stones are then placed at the bottom
as shown in figure 2-8.
of the hole with smaller stones on top up to
(2) Construction details.
the level of the ground (fig. 3-9). The sump
(a) Fire step. The depth to the fire step
may simply provide a collecting basin from
will vary depending on the height of a com-
which water can be bailed.
fortable firing position for the occupant, usual-
(c) Grenade sump. A circular grenade
ly 105 to 150 cm (31/2 to 5 ft). The occupant,
sump 20 cm (8 in. in diameter), 45 cm (18
crouched in a sitting position on the fire step,
in.) long, and sloped downward at an angle
2-4
AGO 20013A
FM 5-15
camouflage cover for the foxhole. This can be
.
E ;G
O$
>
ijJ/
a light, open frame of branches garnished with
grass or other natural foliage to match the-sur-
roundings,-As an alternate method, the fox-
hole can be covered with a shelterhalf, poncho,
or other expedient material, and further cov-
30
WIDE ELBOW
ered with snow or some other material, accord-
ing to local terrain conditions (fig. 2-9). The
s ,
ANTO(gVAR
I:A
occupant raises one side of the cover for ob-
servation or firing.
(f) Overhead cover. A half-cover (fig. 2-
/G~'~
;.ADE SUU10)
over a one-man foxhole provides good pro-
tection for the occupant and permits full use
of.',
30°5<m
of the weapon. Logs, 10 to 15 cm in diameter
or 15 cm (6 in.) timbers approximately 1.2
meters (4 ft.) in length, support the earth
e
dcover.
They should be long enough to extend
WANT sTOWR toD
at least 30 cm (1 ft.) on each side of the fox-.
GRENADE SUMP
GRENADESUMPO.
LONG
hole to provide a good bearing surface. Dirt
should be removed on each side of the foxhole
so that the supporting logs or timbers are even
Figure 2-8. One-man foxhole.
with the ground surface. If the ground is soft
of 300 is excavated under the fire step begin-
and tends to break away, a bearing surface
ning at the lower part of the fire step riser.
of planks or timbers should be provided for
'Handgrenades thrown into the foxhole are ex-
cover supports. Logs or timbers of this size
ploded in this sump, and their fragmentation
will support an earth cover 30 to 45 cm thick.
is restricted to the unoccupied end of the fox-
The walls of the foxhole should be stabilized
hole. For good drainage and to assist in dis-
with revetment material (fig. 2-11) at least un-
posing of grenades, the fire step is sloped to-
der the overhead cover to prevent a cave-in
ward the water sump, and the bottom of the
from the added weight of the cover.
water sump is funneled downward to the gre-
(g) Revetmet material. Use of differ-
nade sump.
ent types of reverting material are shown in
(d) Parapet. If excavated spoil is used
figure 2-11. Expedient material, such as brush-
as a parapet
2(fig.
2-7), it should be placed as
wood, saplings, sheet metal, or dimensioned
a layer about 90 cm (3 ft.) wide and 15 cm
lumber should be thin and tough so that it will
(6 in.) high all around the foxhole leaving an
elbow rest (berm) of original earth about 30
cm (1 ft.) wide next to the foxhole. If sod or
.
topsoil is used to camouflage the parapet, the
sod or topsoil should be removed from the fox-
hole and parapet area, set aside until the para-
pet is complete, and then placed on top in a
natural manner.
(e) Camouflage. Whether or not a para-
pet is constructed in wooded or brushy type ter-
rain, a foxhole can be camouflaged effectively
with natural materials, as shown in figure 2-
9. In open or cultivated areas, it may be prefer-
Q FOXHOLE WITH CAMOUFLAGE
COVER IN PLACE
able to omit the parapet, remove the excavated
spoil to an inconspicuous place, and improvise a
Figure 2-9. Camouflaged one-man foxhole.
AGO 20013A
2-5
FM 5-1S
BRUSHWOOD
()
METHOD OF CONSTRUCTING
COVER
Figure 2-9-Continued.
CHICKEN WIRE AND BURLAP
Figure 2-11. Types of revetting material.
of barbed wire or 14 gauge wire attached to
anchor stakes (fig. 2-12). Five or six strands
of wire should be stretched between the revet-
ment and anchor stakes at ground level and
tightened by twisting. The distance between the
revetment and anchor stakes should be approx-
imately twice the depth of the excavation. The
wire between the stakes should not pass over
w__
I,.wr
the parapet in any case.
ENEMY
Figure 2-10. One-man foxhole with half-cover.
ANCHORWIRE
--
2im (MIN)
support the sides of the emplacement when
properly staked and tied.
,,
ANCHOR
1. Stakes. Revetment stakes, either
STAKE
metal or wood 1.8 meters (6 ft.) in length,
SPACED 30oc
APART
should be spaced not more than 60 cm (2 ft.)
REVETMENT MATERIAL
apart and driven into the ground 30 to 45 cm.
AP ED
REVETENT
ICKET
(APP~ROX)7Pm .
L.SM REVETMENT PICKET
2. Anchor stakes. The revetment
4fCm IN GROUND
stakes are held firmly in place by anchor wires
Figure 2-12. Supporting and anchoring revetment.
2-6
AGO 20013A
FM 5-15
S.a SOO CAVUFLAGE
(3) Open two-man foxhole. In a defensive
TO BLEND WITH TERRAN
position, the two-man foxhole (fig. 2-13) is
CARDOOAO
generally preferred to the one-man emplace-
ment.
2o0m DA BY
TWO MAN FOXHOLE
16O8e LONG LO1
2.
Iafdrlrt
f
: I,
o s FOVarinable
s e
tSI
otNer
obn
SUMP
GRENADE
SUIMP
4 5LN
M DnAT A 3 ANGLe
WArER SUMP
ITh O SLMNT
TOWAR MEN ESUMP
Figure 2-14. Two-man foxhole with offset.
Figure 2-1e. Open two-man foxhole.
(a) Advantages.
1. One man can provide protection
while the other is digging.
2. It affords relief and rest for the
occupants. One man rests while the other ob-
serves. In this manner, firing positions can be
effectively manned for longer periods of time.
3. If one soldier becomes a casualty,
the position is still occupied.
4. The psychological effect of two men
together permits positions to be occupied for
longer intervals.
(b) Disadvantages.
I
1. If a direct hit occurs, two men will
become casualties instead of one.
Figure 2-15. Two-man foxhole with offsets
constructed
2. The area that can be occupied may
of timber and culvert.
be reduced significantly.
(c) Construction. The two-man foxhole
2-5. Fields of Fire
is constructed the same as the one-man fox-
a. Principles. There is little opportunity to
hole except for the location of the grenade
clear fields of fire when a unit is in contact
described in figure 2-14. An alternate method
sitions for expected contact with the enemy,
is shown in figure 2-15.
suitable fields of fire are cleared in front of
AGO 20018A
2-7
FM 5-15
each position. The following principles are
(3) Thin or remove dense brush since it
pertinent:
is never a suitable obstacle and obstructs the
(1) Excessive or careless clearing will dis-
field of fire.
close firing positions (fig. 2-16).
(4) Cut weeds when they obstruct the
(2) In areas organized for close defense,
view from firing positions.
clearing should start near the position and
(5) Remove brush, weeds, and limbs that
work forward at least 100 meters or to the
have been cut to areas where they cannot be
maximum effective range of the weapon if time
used to conceal enemy movements or disclose
permits.
the position.
(3) A thin natural screen of vegetation
(6) Do only a limited amount of clearing
should be left to hide defensive positions.
at one time. Overestimating the capabilities of
the unit in this respect may result in a field
of fire improperly cleared which would afford
the enemy better concealment and cover than
the natural state.
(7) Cut or burn grain, hay, and tall weeds.
7.
--
-*.
ORIGINAL TERRAIN
WRONG.-AFTER IMPROPER CLEARING
WRONG-TOO MUCH CLEARING. DEBRIS
*~
e~
=~ ,,_~~
-~
-.-
~~
INOT
REMOVED. ENEMY WILL AVOID
in
RIGHT-AFTER PROPER CLEARING
Figure 2-16. Clearing fields of fire.
b. Procedure.
(1) Remove the lower branches of large
scattered trees in sparsely wooded areas.
(2) In heavy woods, fields of fire may
RIGHT-NLY UNDERBRUSH AN
TREES
neither be possible nor desirable within the
IN LINE OF FIRE REMOVED. ENEMY SURPRISED
time available. Restrict work to thinning the
Figure 2-17. Clearing fire lanes.
undergrowth and removing the lower branches
of large trees. Clear narrow lanes of fire (fig.
(8)
Whenever possible, check position
2-17), for automatic weapons.
from the enemy side to be sure that the posi-
2-8
AGO 20018A
FM S-15
tions are effectively camouflaged and they are
not revealed by clearing fields of fire.-
Section III. CREW-SERVED INFANTRY WEAPONS EMPLACEMENTS
2-6. Principal Considerations
a. Firing Positions. While it is desirable to
give maximum protection to personnel and
equipment, the principal consideration must be
the effective use of the weapon. In offensive
combat, infantry weapons are sited wherever
natural or existing positions are available or
where weapons can be emplaced with a mini-
mum of digging. The positions described in this
section are designed for use in all types of ter-
rain that will permit excavation.
ENME
b. Protection. Protection
of crew-served
weapons is provided by emplacements which
give some protection to the weapon and crew
while in firing positions. As the positions are
,
developed, the emplacements are deepened and
provided with half overhead cover, if possible.
-s
Then, if the positions are occupied for an ex-
tended period of time, shelters adjoining the
E
emplacement or close to it should be built.
-
d
Characteristics of crew served infantry weap-
ons empacements are shown in table 2-1.
Located in Back of Manual
e. Crew Shelters. Shelters immediately ad-
joining and opening into emplacements im-
PARA
prove the operational capability of the crew,
since the men are not exposed when moving
between the shelter and the weapon.
2-7. Machinegun Emplacements
a. Pit Type. The gun is emplaced initially in
a hasty position (fig. 2-18).
Figure 2-18. Plan vime
and cross section of
b. Horseshoe Type. The dimensions and lay-
machinegun emplacement.
out of the completed emplacement are shown
to the gun position as illustrated in figure 2-
in figure 2-19. The horseshoe shaped trench,
20. The parapet is low enough for all-round
about 60 cm wide, is dug along the rear and
fire and good protection for the crew. A fox-
sides, leaving a chest-high shelf in the center
hole is dug for the gunner at the rear of the
to serve as the gun platform. The spoil from
gun and another foxhole is dug for the assist-
this trench is used to form the parapet, making
ant gunner on the left of the gun and 45 cm
it at least 1 m wide and low enough to permit
(18 in.) in front of the gunner's foxhole. The
all-round fire. This type emplacement permits
spoil is piled all around the position to form a
easy traverse of the gun through an arc of
parapet, care being taken to pile it so as to
180°, but the crew cannot fire to the rear ef-
permit all-round fire of the weapon. Although
fectively.
360° fire is possible from this position, fire to
c. Two One-Man Foxhole Type. This em-
the front or rear is most effective since the
placement consists of 2 one-man foxholes close
M60 machinegun is fed from the left side.
AGO 20013A
29
FM 5-15
PARAPET Im WIDE
ALL AROUND
BERM ABOUT 15cm WIDE" ,
)
GUN PLATFORM
-- ENEMY
lm x Im (M-
CHEST HIGH
l,'
DIG HORSESHOE SHAPED
TRENCH 60cm WIDE
Figure 2-19. Horseshoe type emplaemsnt.
Figure 2-20. Two one-man foxhole type machinegun
emplacement.
2-8. Emplacements for Recoilless Weapons
(2) Two two-man foxhole type. The em-
a. Types. Two types of open emplacements
placement shown in 2, figure 2-21 provides
for recoilless weapons are the pit type and the
limited protection for the crew against nuclear
2 two-man foxhole type.
effects and armor except when actually firing.
(1) Pit type. This emplacement is a cir-
b. Blast Effects. Due to the backblast effects
cular pit about 1.2 meters in diameter and about
of the recoilless weapon, it should not be fired
1 meter deep depending on the height of the
from a confined space such as a fully covered
occupants. A parapet should not be constructed
emplacement. Because the backblast will re-
for this emplacement because of the backblast.
veal the firing position, alternate firing posi-
It is large enough for two men and permits
tions with connecting trenches should be con-
the assistant to turn with the traversing weap-
structed if there is sufficient time.
on, to avoid being behind it when it is fired.
The emplacement is shallow enough to permit
2-9. Mortar Emplacements
the rear end of the weapon to clear the top at
a. General. The emplacement illustrated in
maximum elevation, thus insuring that the hot
1, figure 2-22 is circular in shape. The em-
backblast of the rockets is not deflected to the
placement is excavated to the dimensions
occupants. Since this emplacement offers protec-
shown with the sides of the emplacement slop-
tion for the crew against direct fire weapons
ing inward toward the bottom. The floor
only, supplementary personnel emplacements
slopes to the drainage sump located under the
should be provided (1, fig. 2-21).
open gap in the parapet. An ammunition ready
2-10
AGO 20018A
FM S-15
,_------
-
..
.=bags
and the improved emplacement is revetted
S:x
TRENCH
S
c
t=--'IA.
1m
using corrugated metal. Before constructing
TRENCH
W
wtl:>the
parapet, the mortar is laid for direction
FIRE STEP 3Ocm
of fire by the use of an aiming circle or al-
~....,,m.,,,,,,,,.,,,
ternate means. Aiming posts are then normally
DI A.60cm
"
OX
placed out at a referred deflection of 2,800 mils.
The parapet is then constructed, leaving a 1-
I
'
OAPPOX)
meter gap for the line of sight. This imaginary
, l
if :--
'''
line of sight should be so positioned that it is
30 cm from the right edge of the gap. This
SHELTER,
"
|
C
will allow an approximate 1,500-mil sector of
%%,
*.~ /
fire without moving any portion of the parapet.
The parapet should be not more than 50 cm
-: L, -
a-/
ENTRANCE
TRENCH
high and a minimum of 90 cm wide. Dirt
:tTt= /'XHOL
1.
should not be placed within 45 cm of the edges
-\ "",,,,,,,
DISTANCE FROM PIT
of the sighting gap; in order that sandbags
5, TWO-MAN
FOXHOLE
WITH
I", W
OFFSET
-A
positioned here may be removed to provide a
......
,,,,,,,
_
greater sector of fire when necessary. An exit
(DPIT TYPE ........
trench may be constructed leading to person-
nel shelters and to other mortar positions.
Figure 2-21. Emplacement for recoilless weapons.
LINE OF SIGHT (MY BE
COINCIDENT WITH ENTRYWAY)
4cmI EARTH
4
COVER
NOT
TW.
Mortar emplacements.
I
,
'
,.
Figur I 21
0
'
RmE
S
WEAPO
4.2
-1.3 /I,
(NOT
TO SCALE)
Q CIRCULAR TYPE
©
TWO TWO-MAN FOXHOLE
TYPE
Figure 2-2,. Mortar emplacement8.
Figure e2-21-Continued.
b. The 81-mm Mortar. A pit type emplace-
rack or niche, located so that it is convenient
ment for the 81-mm mortar is shown in 2,
for the gunner, is built into the side of the
figure 2-22.
emplacement. The bottom of the ammunition
c. Emplacement for 4.2-Inch Mortar. The
rack is elevated from the floor of the emplace-
4.2-inch mortar emplacement is identical to
ment. Another ready rack may be constructed
the one described above for the 81-mm mortar
in one side of the trench leading to the position.
except for dimension changes shown in 1, fig-
The initial emplacement is revetted using sand-
ure 2-22.
AGO 20018A
2-1 1
FM 5-15
FRONT EDGE OFt
l{ I
EMPLACEMENT SLOPED T7
CLEAR LINE
F SIGHT TO
AIMING POSTS 50 8 IOm
AMINO POSTS
IN FRONT OF WEAPON
PRINCIPA
PI TYPE
1 2 ' >
DIRECTION
'Rifle
t3.6n
. 5 m4.5m
(g) PIT
TYPE
2-10. Emplacement for 106-mm Recoilless
Rifle
This weapon is often fired from its !/-ton
truck mount since the weapon should be mobile
Figure 2-23. Enplacemnent for 106-mm rifle.
and moved to a new position after firing a
few rounds. In a defensive operation several
so the vehicle can move out quickly. Emplace-
open pits should be constructed with concealed
ments of this type require approximately 30
routes from these firing positions to a con-
man-hours to construct since alternate posi-
cealed shelter position with overhead cover.
tions are required, so the necessity for using
The weapon remains in the shelter until
heavy equipment is obvious. Figure 2-23 illu-
needed, then after firing, it is moved to an-
strates an emplacement for the 106-mm recoil-
other firing position or back to its shelter. The
less rifle which will permit the weapon muzzle
firing pit should protect the sides and front
to extend over the parapet to preclude damage
of the body of the vehicle with the rifle above
to the vehicle from the muzzle blast.
the parapet level. The rear should be ramped
Section IV. VEHICLE AND ARTILLERY EMPLACEMENTS
2-11. Typical Vehicle Pit
Digging in should be restricted to essential
vehicles. Vehicle pits should be as narrow and -
as short as the vehicle size permits. They
should be oriented randomly. All canvas should-
_ -
be removed and the top of the trucks should beE
-OPE
at least 30 cm below the top of the surround-
ing parapet. The excavations should be as
Figure 2-24. Typical vehicle pit.
shown in table 2-2 and figure 2-24. Use of
as well compacted as possible. The majority
soil in construction of the parapet reduces the
of vehicles should be concealed or camouflaged,
depth of cut necessary to properly protect a
with advantage taken of natural features such
vehicle. The parapet should be streamlined and
as woods, defilade, hedgerows, and buildings.
2-12
AGO 20013A
FM 5-15
Table 2-2. Dimensions of Typical Vehicle Pits
%-ton truck
4-ton track
and trailer.
2%-ton truck
5-ton truck
and trailer,
ith radio
and trailer,
and trailer,
ans down
shelter
canvas down
helcanvas
downnv
down
Depth of cut (C) -..
.
.. 0.9 meters
1.8 meters
1.5 meters
1.5 meters
Width of pit -
2.4 meters
3.0 meters
3.5 meters
3.6 meters
Level length of pit (L) ------
6.0 meters
8.1 meters
10.5 meters
10.8 meters
Thickness of parapet (H) -----
60 cm
75 cm
75 cm
75 cm
Width of parapet (P) .-
.....
1.2 meters
2.4 meters
2.7 meters
2.7 meters
Exit slope (A:B)* '
1:1
2:1
2:1
2:1
Total excavation -19
cubic meters
61 cubic meters
71 cubic meters
76 cubic meters
Equipment hours**
0.4
0.8
0.9
0.9
*Entrance slope 1:1.
**For cut and rough parapet construction only, at appropriate rates for D7 or DS type
bulldozers.
2-12. Towed Artillery Weapons
(4) Stage 4. In this stage revetment is
a. Purpose. Emplacements
for artillery
provided for the ground fighting positions and
weapons must provide maximum flexibility in
for the outside and top of the parapet. Over-
the delivery of fire and protect the weapon
head cover is also provided for the personnel
and its crew against the effects of conventional
ready position and the ammunition shelter.
and nuclear weapons.
Stage-four emplacement for a 105-mm howit-
b. Emplacement for 105- and 155-mm
zer is illustrated in 4, figure 2-25 and 2, figure
Howitzer. Artillery
weapons
emplacements
2-26. Dimensions and layout are also shown
are constructed so as to allow for continuous
in figure 2-26.
improvement in order to provide additional
(5)
Use of overhead cover. It is usually
protection and comfort in the event of pro-
difficult to provide overhead cover for artil-
longed occupation. These emplacements are
lery weapons. The widths and heights involved
developed in stages as described in (1) through
make such
construction
impractical under
(4) below.
most conditions. Overhead cover would unduly
(1) Stage 1. This stage provides open
restrict the firing capability of the weapon. In
foxholes for the protection of the crew and
addition, under most conditions, it is not de-
open emplacements for infantry weapons used
sirable to excavate an emplacement for the
to defend the position. Provision is made for
weapon much below ground level or to con-
only minimum essential shifting of the gun
struct a high all-round parapet for the fol-
trail and ammunition is stored in the open.
lowing reasons:
Stage-one emplacement for a 105-mm howitzer
(a) A high all-round parapet restricts
is illustrated in 1, figure 2-25.
the direct fire capability of the weapon.
(2) Stage 2. This stage provides trail logs
(b) An emplacement excavated below
for all around traverse of the weapon, a low
ground creates difficulty in rapid removal of
parapet to protect the weapon, and covered
the weapon from the emplacement.
ermplacements for the crew, defensive weap-
c. Accessory Structures.
ons, and ammunition. Stage-two emplacement
(1) Ammunition shelters. Sectional shel-
for a 105-mm howitzer is illustrated in 2, fig-
ters as shown in figure 3-13 may be used with
ure 2-25.
overhead cover as ammunition shelters with
(3) Stage 3. In this stage a parapet re-
the types of weapons emplacements discussed
vetted on the inside which permits all around
above.
direction fire is provided. Work is begun on
(2) Accessory shelters. Ready shelters
covered shelters for personnel and ammuni-
for personnel and shelters for fire direction
tion. Stage-three emplacement for a 105-mm
centers and switchboards are constructed us-
howitzer is illustrated in 3, figure 2-25.
ing standard shelter designs (ch 3).
AGO 20018A
2-13
FM 5.15
4:~
~~~~~~~~~~~~~
',
;.¥
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A,
(:
K
r
it
2-14
AGo 20018.4
FM 5-15
i~,
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h~
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< :1.
II t4 M~~~~~~,,
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.L ~
-,.ii
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:
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i-15
it:~~~~~~~~~~~~~~~~~~~~~~~~~
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·
~E
..
24
12
fr
AGO
20018A
2-15~i't,
FM 5-15
'I''~~~~~~~~~~~~~~~~~~~~~~~·"
,-16
2-16
AGO 20018A
FM 5-15
;I
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,
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, ).
..
,,.
,
*;# ;,,,i,
/ -ttl
:own 4t'
,
,,..
r'
:~~~
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·
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nb
t.Ss
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<~~~~~~~~~--
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20013A
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AGO
20013A
S
FM S-15
STEP O
2-13. Self-Propelled Artillery and Tank.
120cm_l
1.-
7.2m
| GROUND
LINE
Mounted Weapons Emplacement
45 cm
/
Sdl.'.ir,
-"z
a. Self-Propelled Artillery. Large caliber
60 cm:,
", ':':'1i~''
self-propelled weapons have a limited traverse
without turning the vehicle. For this reason it
is seldom practical to construct emplacements
for this type of weapon. When positions for
self-propelled weapons are prepared, a sloped
ramp is built to facilitate the vehicle's entry
into and withdrawal from the gunpit. In ex-
RAMP
24m
tremely cold weather, gravel, saplings, or sim-
_5
, S
_
_
_
,
I
ilar covering may be necessary for the floor of
the pit so that the tracks of the vehicles will
\ S''
H'ELTER
% ~"
not freeze to the ground. The rear of the pit
and the sloped ramp should be widened suffi-
.05cm BL
ciently to permit driving the vehicle in at an
GROUND
LEVEL
angle in order to compensate for the limited
BERM IS EXTENDED To
traverse of the weapon.
STEP
E 75cm COVER
b. Tanks. A tank is emplaced or protected in
240cm 05m
the same manner as any other vehicle. Natural
ERANCESL x 105cm
defilades such as road cuts or ditches are used
: ', * , , e
__
where available. In open areas, parapets are
provided to protect the sides and front of the
hull of the vehicle, and the rear is left open.
The simplest form of a dug-in position of this
O
LAYOUT
type is shown in figure 2-27. Wherever possi-
ble, such positions are constructed and occu-
Figure 2-26. Final stage of development, howitzer
pied during darkness, with all camouflage
entplacement.
being completed before dawn. The emplace-
PARAPET DIMENSIONS
ment normally includes foxhole protection for
BASE -
165 cm
relief personnel, preferably connected with the
50 CAL MG
TOP-
90cm
W/M63 MOUNT
HEIGHT-APPROX. 120cm
emplacement by a short trench. A dug-in em-
2
150cm
-
60cm
placement of this type should have the follow-
=Ocm
~ing:
-\2
L)ocm
(1) An excavation deep enough to afford
TRAIL LOGS FTOR
35cm DEEP
protection for the tracks and part of the hull
400M
TRAVEROG
PERONNEL
of the vehicle with maximum thickness of the
AMMUNITION
READY
parapet at the front of the emplacement and
~iSHELiiiTE
P S R the rear left open for entry and exit of vehicle.
\
O
AMMUNITIO
N ,¢
0
OSTOVE
(2) Inside dimensions just large enough
UMP
AC ADUBLE
SUMP
to permit entry and exit of vehicle.
lPl=,o,/jcN
l
OEK
(3)
An inside depth permitting the
I: St,|
ESCAPE HATCH
weapon to depress to its minimum elevation.
Tank emplacements must have sufficient space
IIEARTH HEAPED AGAINST
the torage of ammunition.
DRAIN FROM TRAIL
LOG REVETMENT, COVERED
MLOG REVETENT, COVERED
for the storage of ammunition.
FROM
lOS MM
PREVENT EROSION
STEEL CANNISTERS
fire into adjacent units.
(5) Provisions for drainage (if possible)
and frostproof flooring to prevent tracks from
Figure 2-2r6-Continued.
freezing to the ground.
2-18
AGO 20018A
FM 5-15
(6) If it is necessary to deliver fire at
radial sleepers (fig. 2-28). The wooden pad
elevations higher than permitted by the car-
distributes the load over a large area with no
riage design, the floor must be sloped up in
significant settlement and is flexible and strong
the direction of fire.
enough to withstand the turning and move-
ment of self-propelled weapons. The trail logs
are anchored just outside the pad for towed
-A
-
i,
A
weapons. For self-propelled weapons, the re-
,'*IrJ;+QNWfIglo
gI
AiN N
coil spades can be set in compacted material
or a layer of crushed rock just off the pad. A
pad of this type does not take long to con-
struct if materials are pre-cut and assembled
on the site. Revetments and shelters can be
-'-
i
-
4
2-
constructed as described in paragraph 2-12.
12.20 MITR S (4')
OIAM SELF PROPL I
15 S IN 175
"6I0
MElS20') DIAM 10 MM HOWITZER
SPOIL
.
PLAN VIEW
SPOIL
LEVEL
SECTION
A-A
CAMOUFLAGE NOT SHOWN
Figure 2-27. Dug-in emplacement for self-propelled
weapon.
TOP
&
'oTo
LAY ERS S CM
2 LAYERS OF
LUMBER
5 LM tUMBE
2-14. Artillery Emplacements in Soft-Ground
The siting of artillery positions in areas where
the ground is soft require the construction of
pads to preclude differential settlement and
thus the relaying of the weapon after each
2Ox30 CM
SLEEPER
round is fired. Wooden pads can be constructed
Figure 2-28. Load distribution pad for artillery
of two layers of 5-cm lumber with 20- x 30-cm
emplacements in soft ground.
Section V. AIRCRAFT REVETMENTS
2-15. Introduction
2-16. Types of Revetments
Often it is necessary to protect parked aircraft
a. Sandbag. Revetments constructed with
from damage by small arms fire, recoilless
filled sandbags are a practical expedient for
rifles, and mortar fragments. The most practi-
fortifications, particularly when equipment is
cal type of protective emplacement that can be
limited to handtools and when skilled super-
constructed is the three-sided revetment. Sev-
visory assistance is not available to supervise
eral types are discussed here in general. For
the construction of other types of structures.
exact requirements and design procedures
The bags can be filled at the construction site
refer to TM 5-330.
with sand hauled to the location, which is
AGO 20013A
2-19
FM 5-15
preferable, or they can be filled where the sand
(fig. 2-30). The sides have a 1:1 slope or
is available and hauled to the site. The latter
sloped at the angle of repose and are covered
procedure increases possible damage to the
with a waterproof coating. The top of the
bags during handling. Sandbags deteriorate
revetment should have a 10:1 slope to facilitate
rapidly, particularly in damp climates, permit-
drainage.
ting filler material to run out, causing a con-
sequent reduction of protective characteristics
and endangering the stability of the revet-
ment. Shell hits have a similar effect, requiring
replacement of bags. Sandbags may be stacked
without a retaining wall if the sides of the
revetment are sloped approximately 1:4. The
substitution of a soil cement mixture, or coat-
ing the bags with a cement slurry will par-
A
tially overcome deterioration of the sandbags,
which is the principal disadvantage of this
PLAN
type of fortification.
MINIMUM PENET
R-TIO
b. Gravity. This type of revetment is con-
THICKNESS
IT}
I10:1
SLOPE
structed of compacted earthfill placed against
a retaining wall (fig. 2-29). The unconfined
earth side must have a 1:1 slope or be sloped
WATERPROOF
COAT
at the angle of repose. The top of the revet-
SORD
CTi
ment has a slope of 10:1 to facilitate drainage.
GRADE
To prevent erosion and keep the fill dry, the
SECTION A-A
top and sides are waterproofed using asphalt
SECTION A-A
cutback or cement slurry. Traffic on the revet-
ment must be prohibited in order to preserve
the waterproof coating. Sod can be used to
prevent erosion, but moisture is allowed to en-
NOTE:
WATERPROOFING UAY BE ASPHALT
CUTBACK OR CEMENT SLURRY.
ter the fill and will cause a decrease in protec-
TRAFFIC ON THE REVETMENT WST BE PROHIBITED
IN ORDER TO
tion against penetration by projectiles.
PRESERVE THE WATERPROOF MATING.
Figure 2-80. Earth revetment.
l.,
|>Cd.
Bulkhead. This revetment consists of two
|o" acr I
_
retaining walls with earthfill placed between
r r*
_
them (fig. 2-31). After both inner and outer
wall sections are completed and placed up-
/ XCABLE S
right, sturdy spacer blocks are used to hold
o0'
/T
;s,
the walls apart at the specified distances while
se
..j-
_ S
the tie cables are tightened. The filler material
is carefully deposited to avoid displacing the
t .
:
spacer blocks. A waterproof cover must be ap-
LO^
X
plied to the top of the revetment to keep the
fill dry.
e. Free Standing Wall. This revetment can
be constructed of either soil cement (fig. 2-32)
or reinforced concrete (fig. 2-33). This type
of revetment is the most durable but it is the
Figure 2-29. Gravity revetment.
most difficult to construct. Skilled workers and
c. Earth. The malls of this revetment are
supervisors are required to build the forms,
constructed entirely of compacted earthfill
place the reinforcing bars, and place the con-
2-20
AGO 20018A
FM 5-15
crete. Large amounts of cement and reinforc-
ing bars are required and these items are usu-
ally in short supply in the theater of opera-
S
T
'
tions. The exposed surfaces of the soil cement
wall must be waterproofed.
10:1 SLOPE
_
I.
T(2'MIN)
RSPCarED
_
SLOPE
0
|
.FOOTER
MAY BE NECESSARY
pa~,~~~
.~:~~i~~
EARTH'~
~
EXPOSED SURFACES
WATERPROOFUI G
NOTE, WALL
TIES SAME SIZE AS
Figure 2-32. Free standing wall-soil cement revetment.
ANCHOR CABLES
Figure 2S1.
Bulkhead revetment.
2-21
AGO 20013IA
FM 5-15
A1
Per section
3"I I I I
Clear
_ _ _
I I_
___4(_"_)
bars
_/I _
i
,
_ _ _ _ _
_ ____both
ways
H
i
both faces
i-ll
l
……
T…T…| | | | | | |||Groundline
-- \~
~~ r~tst~~sv.A~.
E
Clear
""' Clear
T (I' min)
NOTES
I. Each section butted
but not jointed to
adjacent sections
2. Width of footer varies
H
with soil bearing
capacity
3. Spacing of footing
reinforcing bars
I H
F.
F
+
H
will depend on
J 4
It4
t
detail design
1'Groundline
4t~'K1
_
'-*
-
12" Min
4'
'l
3" C
rClear
180 H
DETAIL
SECTION A-A
4 (-J' bars )
Figure 2-S3.
Free standing wall-reinforced concrete revetment.
2-22
AGO 20018A
FM 5-15
CHAPTER 3
SHELTERS
Section I. HASTY SHELTERS
3-1. Basic Considerations
of the ground or when the surface is so hard
a. Protection. Shelters are constructed pri-
that digging an underground shelter is im-
marily to protect soldiers, equipment, and
practical.
supplies from enemy action and the weather.
c. Underground Shelters. Shelters of this
Shelters differ from emplacements because
type generally provide good protection against
there are usually no provisions for firing weap-
radiation because the surrounding earth and
ons from them. However, they are usually con-
overhead cover are effective shields against
structed near or supplement the fighting
nuclear radiation.
positions. When natural shelters such as caves,
d. Cut-and-Cover Shelters. These shelters
mines, woods, or tunnels are available, they
are dug into the ground and backfilled on top
are used instead of constructing artificial shel-
with as thick a layer as possible of rocks, logs,
ters. Caves and tunnels must be carefully in-
sod, and excavated soil. These and cave shel-
spected by competent persons to determine
ters provide excellent protection from weather
their suitability and safety. The best shelter is
and enemy action.
usually the one that will provide the most pro-
e. Siting. Wherever possible, shelters should
tection with the least amount of effort. Ac-
be sited on reverse slopes, in woods, or in some
tually, combat troops that have prepared de-
form of natural defilade such as ravines, val-
fensive positions have some shelter in their
leys, and other hollows or depressions in. the
foxholes or weapon emplacements. Shelters
terrain. They should not be in the path of
are frequently prepared by troops in support
natural drainage lines. All shelters must be
of frontline units. Troops making a temporary
camouflaged or concealed.
halt in inclement weather when moving into
3-2. Construction
positions prepare shelters as do units in biv-
a. Principles. Hasty shelters are constructed
ouacs, assembly areas, rest areas, and static
with a minimum expenditure of time and labor
positions.
using available materials. They are ordinarily
b. Surface Shelters. The best observation is
built above ground or dug in deep snow. Shel-
from this type of shelter and it is easier to
ters that are completely above ground offer
enter or leave than an underground shelter. It
protection against the weather and supplement
also, requires the least amount of labor to con-
or replace shelter tents which do not provide
struct, but it is hard to conceal and requires a
room for movement. Hasty shelters are useful
large amount of cover and revetting material.
in the winter when the ground is frozen, in
It provides the least amount of protection
mountainous country where the ground is too
from nuclear weapons of the types of shelters
hard for deep digging, in deep snow, and in
discussed in this manual. Surface shelters are
swampy or marshy ground.
seldom used for personnel in forward combat
b. Sites for Winter Shelters. Shelter sites
positions unless they can be concealed in
that are near wooded areas are the most de-
woods, on reverse slopes, or among buildings.
sirable in .winter because these areas are
It may be necessary to use surface shelters
warmer than open fields. They conceal the
when the water level is close to the surface
glow of fires and povide fuel for cooking and
AGO 20013A
3-1
FM 5-15
the snow, it is necessary only to place a layer
of some insulating material such as a shelter
half, blanket, or other material between the
body and the snow.
-4~---
~3-3.
Types
.
/ 5 _~
~~~~a. Wigwam Shelter. This type of shelter (1,
fig. 3-1) may be constructed easily and quickly
~-, < _ "f
when the ground is too hard to dig and shelter
is required for a short bivouac. It will accom-
,4
4 rn#,',g
'/y
modate three men and provide space for cook-
o~et8;;k,
JI
/t-e,)
.';
~8 f
i
. sjv,
ing. About 25 evergreen saplings (5 to 71/2 cm
vr
in diameter, 3 meters long) should be cut.
O BUILT AROUND A TREE
Figure 3-1. Wigwram.
heating. In heavy snow tree branches extend-
ing to the ground offer some shelter to small
4.5 5m
......
units.
c. Materials.
(1) Construction. Work on winter she]-
QBUTT ENDS LASHED
ters should start immediately after the halt so
that the men will keep warm. The relaxation
Figure S-1-Continued.
and warmth offered by the shelters is usually
Leave the limbs on the saplings, and lean them
worth the effort expended in constructing
against a small tree so the butt ends are about
them. Beds of foliage, moss, straw, boards,
2 meters (7 ft.) up the trunk. Tie the butts
skis, parkas, or shelter halves may be used as
together around the tree with a tent rope, wire,
protection against dampness and cold from the
or other means. Space the ground end of the
ground. Snow should be removed from clothing
saplings about 30 cm (1 ft.) apart, around
and equipment before entering the shelter. The
and about 2 meters from the base of the tree.
entrance of the shelter is located on the side
Then trim the branches off inside the wigwam
that is least exposed to the wind, is close to
and bend down on the outside so that they are
the ground and has an upward incline. Plaster-
flat against the saplings. The branches that
ing the walls with earth and snow reduces the
are trimmed off from the inside may be used
effects of wind. The shelter itself should be as
to fill in the spaces that are left. Shelter halves
low as possible. The fire is placed low in fire
wrapped around the outside make it more
holes and cooking pits.
windproof, especially after it is covered with
(2) Insulating. Snow is windproof, so to
snow. A wigwam can also be constructed as
keep the occupant's body heat from melting
shown in 2, figure 3-1 by lashing the butt ends
3-2
AGO 2001aA
FM 5-15
PERSPECTIVE VIEW
LEVEL-
SHELTER
HALF
AT ONE
OR BOTH
SIDE VIEW
ENDS
Figure 3-2. Lean-to shelter.
Of the saplings together instead of leaning
a steep hillside, a deadfall, or some other exist-
them against the tree. _
ing vertical surface, on the leeward side. The
b. Lean-to Shelter. This shelter (fig. 3-2)
ends may be closed with shelter halves or ever-
is made of the same material as the wigwam
green branches.
(natural saplings woven together and brush).
c. Two-Man Mountain Shelter. This shelter
The saplings are placed against a rock wall,
(fig. 3-3) is useful, particularly in winter or
AGO 20012A
3-3
FM 5-15
e. Snow Cave. Snow caves (fig. 3-5) are
3_
made by burrowing into a snowdrift and fash-
ioning a room of desirable size. This type of
-.
a.
0t-r~
c
-~-
shelter gives good protection from freezing
weather and a maximum amount of conceal-
+<j
V-~
-.
o.ment.
The entrance should slope upward for
the best protection against the penetration of
cold air. Snow caves may be built large enough
for several men if the consistency of the snow
is such that it will not cave in. Two entrances
can be used while the snow is being taken out
of the cave; one entrance is refilled with snow
when the cave is completed.
Figure -3. Two-man mountain shelter.
: ..
in inclement weather when there is frequent
.
rain or snow. It is basically a hole 2 meters
.t
long, 1 meter wide, and 1 meter deep. The hole
is covered with 15 to 20 cm diameter logs;
V
i"
.
then evergreen branches, a shelter half, and
.;'
local material such as topsoil, leaves, snow,
and twigs are added. The floor may be covered
.-
.--
with evergreen twigs, a shelter half, or other
.
expedient material. Entrances are provided at
both ends if desired. A fire pit may be dug at
;,
:
one end for a small fire or stove. A low earth
.
'
.
parapet is built around the emplacement to
J:
provide more height for the occupants. This
'
shelter is very similar to an enlarged, roofed,
prone shelter (fig. 2-7).
d. Snow Hole. The snow hole (fig. 3-4) is a.
.
simple, one-man emergency shelter for protec-
tion against a snow storm in open, snow-
covered terrain. It can be made quickly, even
without tools. Lying down in snow at least
.
.
.
I meter deep, the soldier pushes with his feet,
digs with his hands, and repeatedly turns over,
forming a hole the length of his body and as
wide as his shoulders. At a depth of at least
.
:
,
,.b
1 meter, the soldier digs in sideways below the
.
surface, filling in the original ditch with the
snow that has been dug out until only a small
opening remains. This opening may be entirely
?~i
closed, depending on the enemy situation and
the temperature; the smaller the hole, the
warmer the shelter.
Figure 3-4. Making a snow hole without tools.
3-4
AGO 2001oA
FM 5-15
walls consist of snowblocks and may be built
to the height of a man. Snow piled on the
outside seals the cracks and camouflages the
house (fig. 3-7).
.=2
"-
,-.,
--
i
-
,,I
'o1N
SNOW
BLOCK
Figure 3-7. Snowhouse with iceblock walls.
,"~DOOR
EMPIN?_;
=LTFORM
-?
,
p
:
-3-4.
Tropical Shelter
~ -2COLD_
~=__
_
AIR LEV
...
A satisfactory bed and rain shelter (fig. 3-8)
may be constructed in a short time from nat-
Figure 3-5. Snow cave.
ural materials. The bed itself is made first
about 1 meter above the ground. Four forked
f. Snowpit. The snowpit (fig. 3-6) is dug
stakes, about 1.5 meters long and 5 cm in
vertically into the snow with intrenching tools.
It is large enough for two or three men. Skis,
dameter, are dren into the ground. Then,
poles, sticks, branches, shelter halves, and
a timber framework lased together
with
snow are used as roofing. The inside depth of
Stout and pliable reeds, such as bamboo shoots,
the pit depends upon the depth of the snow,
are laid over the framework and covered with
but should be deep enough for kneeling, sitting,
er the framework and covered with
several layers of large, fine ferns. Four longer
and reclining positions. The roof should slope
stakes are driven into the ground alongside
toward one end of the pit. If the snow is not
deep enough, the sides of the pit can be made
the bed stakes for the roof. There must be
higher by adding
snow walls
some pitch to the roof to permit the rain to
run off. Leaves for the roofing are laid with the
NEW SNOW
butt ends toward the high end of the shelter.
IMPROVISED
ROOF
' ' ..
SNOW
STOUT,,S
. IABLE
EREEDS
LAID AC:OSS FREOK
LbR FORKED
-
I~,
1.6 meters
se
_~
TO\
\\m\\
·
---
$EVERSaL
L
FAYERS
O
END VIEW
(
Figure 3-6. Snowpit in shallow snow.
FRAEWK
.
g. Snowhouse. The size and roof of a snow-
house are similar to those of a snowpit. The
Figure 3-8. Jungle rain shelter.
AGO 20013A
3-5
FM 5-15
Section II. DELIBERATE SHELTERS
3-5. Types
The most effective shelters are deliberate, un-
derground, cut-and-cover or cave shelters.
BAFLE WALL
Shelters should be provided with as deep over-
head cover as possible. They should be dis-
persed and have a maximum capacity of 20 to
25 men. Supply shelters may be of any size,
I
depending on location, time, and materials
available. The larger the shelter the greater
ENRAN
SLOPE
TO
the necessity for easy entrance and exit. Large
shelters should have at least two well camou-
flaged entrances spaced widely apart. The far-
ther away from the frontlines the larger,
b. Ventilation. It is particularly important
deeper, and more substantial a shelter may be
to ventilate cave shelters, especially if it is
constructed because of more freedom of move-
necessary to close the entrances during an at-
ment, easier access to materials and equip-
tack. In surface and cut-and-cover shelters,
ment, and more time to spend constructing it.
enough fresh air usually is obtained by keep-
ing entrances open. Vertical shafts bored from
FLOOR DRAINED OR GRADED
within cave shelters are desirable if not abso-
TOWARDS SUMP
lutely essential. A stovepipe through a shaft
\ ~NOT
LESS THAN
assists the circulation of air. Shelters that are
O LS30cm T
not provided with good ventilation should be
used only by personnel who are to remain in-
active while they are inside. Since an inactive
man requires about 1 cubic foot of air per
. .-
DEPTH NOT
minute, unventilated shelters are limited in
LESS THAN
capacity. Initial airspace requirements
for
30cm
shelters for not over 12 men are 350 cubic feet
per man.
c. Entrance Covering. If gasproof curtains
LARGE STONES
are not available, improvised curtains made of
AT BOTTOM
blankets hung on light, sloping frames may
be used. They should be nailed securely to the
Figure S-9. Sump for shelter drainage.
sides and top entrance timbers. Curtains for
3-6. Construction Requirements
cave shelters should be placed in horizontal
a. Drainage. Drainage is an important prob-
entrances or horizontal approaches to inclines.
lem particularly in cut-and-cover and cave
Windows should be covered with single cur-
shelters. After the shelter is dug, drainage
tains. All crevices should be caulked with clay,
work usually includes keeping the surface and
old cloths or sandbags. Flooring or steps in
rain water away from the entrance, prevent-
front of gas curtains should be kept clear of
oing the water from seeping into the interior
mud and refuse. Small, baffled entrances and/
by ditching, and removal of water that has
or right angle turns will reduce the effects of
collected inside the shelter. The floors of shel-
nuclear blasts and will keep debris from being
ters must have a slope of at least 1 percent
blown in. Baffle walls may be constructed of
toward a sump (fig. 3-9) near the entrance,
sods or sandbags. Materials which may be
while the entrance should be sloped more
injurious to the occupants should be avoided.
steeply toward a ditch or sump outside the
d. Sanitary Conveniences. Sanitary conven-
shelter (fig. 3-10).
iences should be provided in all but air-raid
3-6
AGO 20013A
FM 5-15
emergency shelters and surface-type shelters,
where latrines are available. Disposal is by
'
burial or chemical treatment. When water-
borne sewage facilities are available, disposal -
can be into septic tanks or drainage into
AIR VENT
special sewers.
f
-
'
e. Light Security. Blackout curtains should
be installed in the entrance to all shelters to
.D
:
prevent light leakage. To be most effective,
blackout curtains are hung in pairs so that .::
" .
'
one shields the other. Blankets, shelter-halves,
or similar material may be used for this
DRAINA
GE-
purpose.
DITCH
f. Emergency Exits. Emergency exits in
BOARD
ad
larger shelters are desirable in case the main
WALK
exit is blocked. If possible, the emergency exit
CUT-AND-COVER SHELTER IN A HILLSIDE (BAFFLE WALL OF
should be more blast-resistant than the main
ENTRANCE CAMOUFLAGE OMITTED) SHADED AREA AND
entrance. This can be done by making it just
BROKEN LINES SHOW CUTAND-FILL SECTIONT
large enough to crawl through. Corrugated
pipe sections or 55-gallon drums with the ends
"? F
-.
-
removed are useful in making this type of exit.
:I
A simple emergency exit which is blast resist-
ant can be constructed by sloping a section of
corrugated pipe from the shelter up to the
BOARD
::
surface, bracing a cover against the inside,
WALK
and filling the section of pipe with gravel.
/
/
When the inside cover is removed, the gravel
will fall into the shelter, and the occupants
can crawl through the exit without digging.
DRING
DRAINAGE
7
,
-
'
3-7. Surface Shelters
DITCH
SAND BAGS
A log shelter (fig. 3-11) is constructed in the
.<,_
form of a box braced in every direction. The
CUT-AND-COVER SHELTER IN A CUT BANK SHOWING
SAND-BAGGED OUTER WALL. SHADED AREA AND
15 CM UPRIGHTS
BROKEN LINES SHOW AREA OF CUT-AND-FILL.
Figure 3-12. Cut-anld-cover shelter.
\
|
2.A
0
----
_3
framework must be strong enough to support
a minimum of 45 cm of earth cover and to
withstand the concussion of a near-miss of a
shell or bomb or the shock of a distant nuclear
explosion. The size of the logs used is limited
by the size of available logs for the roof sup-
ports and by the difficulty of transporting
large timbers.
a. Size. Shelters 2 to 3 meters wide by 4.2
SPREADER OR
meters long are suitable for normal use. The
FLOOR
JOINT
shelter shown in figure 3-12 will provide from
1.8 to 2 meters of headroom.
b. Timbers. All timbers should be the same
Figure 3-11. Log framed shelter.
size if possible, approximately 15 to 20 cm in
AGoo
2001A
3-7
FM 5-15
diameter depending on the width of the shel-
ter (table 3-1). The uprights should be ap-
proximately 60 cm apart except at the entrance
where they may have to be spaced further
apart. The roof supports should be spaced the
same as the uprights. Holes should be drilled
for driftpins at all joints.
c. Bracing. Boards 2.5 by 10 cm (1 in. by
4 in.) in size for the diagonal bracing is nailed
to caps, sills, and uprights.
d. Walls. The log shelter frame should be
covered with board or saplings and backfilled
with approximately 60 cm of earth, or a hollow
wall may be constructed around the buildings
and filled with dirt.)
TYPICAL CONNECTION OF THREE SECTIONS
e. Cover. A roof of planks, sheet metal, or
other material is then laid over the roof sup-
6-o"
ports and perpendicular to them to hold a
minimum of 45 cm of earth cover.
Table 3-1. Size of Roof Supports
_-
_
_
Size of timber
Maximum span when used to
(
(diameter)
support 45 em of earth
10 cm
(4 in.) --
-
1.2 meters
(4 feet)
12.5 cm (5 in.)
2.0 meters
(5 feet)
15 cm
(6 in.)
......
2.1 meters
(7 feet)
iE
(4
17.5 cm (7 in.)
.-.....
2.7 meters
(9 feet)
RIGHT SIDE
REAR
20.0 cm (8 in.) -
3.3 meters (11 feet)
22.5 em (9 in.)
.-
.
3.9 meters (13 feet)
(
FRAMING
DETAILS
Figure 3-13. Sectiolal shelters.
3-8. Subsurface Shelters
a. Cut-and-Cover Shelters. The log shelter
the required shelter area. The advantages of
shown in figure 3-11 is suited to cut-and-cover
sectional shelters for the purpose of command
construction or surface construction. The best
posts or aid stations are the flexibility of the
location for cut-and-cover shelters is on the
shelter area that can be provided, the depth of
reverse slope of a hill, mountain, ridge, or
cover the shelter will support, and the fact
steep bank as shown in figure 3-12. The shelter
that the design lends itself to prefabrication.
frame is built in the excavation; the spoil is
The principal disadvantage is the degree of
backfilled around and over the frame to ground
skill required in constructing the sections from
level, or somewhat above, and camouflaged.
dimensional lumber of logs of comparable
The protection offered depends on the type of
strength, necessitating engineer assistance and
construction (size of timbers) and the thick-
supervision.
ness of the overhead cover. As in the case of a
(1) Siting. The shelter should be sited on
surface shelter of similar construction, ap-
a reverse slope for cut-and-cover construction.
proximately 45 cm of earth cover can be sup-
(2) Excavation. Assuming that each bent
ported.
or side unit (fig. 3-13 and table 3-2) is
b. Sectional Shelters. Shelters of the type
sheathed before installation, the excavated
shown in figure 3-13 are designed so that the
area should be 2.1 meters (7 ft.) wide and
6- by 8-foot (1.8 by 2.4 meters) sections may
3 meters (10 ft.) long for one section. The
be assembled for use individually or in com-
additional length of the excavated area will
binations of two or more sections to provide
provide working space to install sheathing on
3-8
AGO 20013A
FM 5-15
RIGHT
FRONT
SIDE
DOORWAY
RIGHT SIDE
REAR
LEFT SIDE
FRONT
O
FRAMING
DETAILS
© SHEATHING
DETAILS
Figure 3-13-Continued.
FRONT
1
under engineer supervision, can be used eco-
nomically at the worksite to excavate the shel-
ter area, assemble the roofing and cover mate-
RIGHT SIDE
rials, and construct the overhead cover. Under
favorable conditions a trained engineer squad
TOP
can excavate the area required for the shelter,
and install the shelter and overhead cover in
18 to 20 hours. However, if a backhoe or
bucket loader is available for the excavation,
(d)-©-
)--
the time can be reduced to approximately 6
hours.
LEFT SIDE
FRONT
ENTRANCE
EXIT
® SHEATHING
DETAILS
Figure 8-13-Continued.
_
----------
-
11
the rear unit. The area for the shelter should
.. -
r---
be excavated to a depth of 3.6 meters (12 ft.)
- ----
'-
to allow for a laminated roof and 3.2 meters
I
(10 ft. 6 in.) for stringer roof (para 3-9)..
(3) Assembly. The two bents or side units
may be assembled and sheathed before they
are placed in the excavated area. In this man-
ner driftpins are installed in the sills, caps CUT -
,
t
and posts before units are placed in the ex-
cavated area. Bracing on the side units as well
as the bracing and spreaders on the front and
rear units are toenailed.
DRAINAGE DITCH
(4) Organization of work crews. An en-
ROAD CUT
gineer squad, or a squad other than engineer
Figure 3-14. Supply cave in a road cut.
AGO 20013A
3-9
FM 5-15
Table 3-2. Bill of Materials for One 6' z 8' Sectional Shelter with Post, Cap and
Stringer Construction-Dimensional Timber
(See Metric System conversion table, app. B)
Material list
Quantities
No.
Nomenclature
Rough size
Roof
Front
Right
Left
Rear
1
Cap or sill
6"x8"x8'0"
--...-..
2
2
........
2
Post
-
6"x6"x5'10"
.
--..... ----
3
3 3
3
Stringer
*
6"x6"x6'0"
16
.........--
4
Spreader
3"x6"x5'0"
2
1
5
Post, door
3"x6"x6'6"
1
6
Brace
*3"x6"x7'0"
-_
.......
1
7
Brace
3"x6"x6'10"
--.. ......--...
...
1
2
8
Brace -.--
*3"x6"x8'0"
2
.....--
9
Spreader
2'x6,x3'3"
..............--...
3
10
Spreader
2"x6"x2'9"
----.....-
--....-
2
11
Spreader
2"x6"x2'0"
.....---..-
--.....--
2
12
Scab
3"x6"x2'
-0" .............
.......
13
Siding _
3"xRWx8'0"
---....................--.....
411SSF
14
Siding
-.-
3"xRWx6'0"
36SF
......
.
.....................
15
Siding
3"'xRWx4'0"
-
--..-..-........
24SF
16
Siding
.
...
3"xRWx3'6"-
.
-...........................---.....
21SF
17
Roll roofing
100 sq ft roll
6
................--
18
Driftpin
M
%"x14"
32
6
6
19
Nails
.
..
60d
8 lb
8 lb
8 lb
8 lb
Allowance for double cut ends of braces is included in overall length as shown under rough size.
*Lanminated
wood roof (fig. 3-17) may be substituted if desired.
cave entrance is showvn in figure 3-14. The
Size of round timber
disadvantages of cave shelters include limited
Size of rectangular
timber
requirel
to equal (in inches)
Si..
6x6
7
r~t~gu.~Ub~
T.ir] u ~~l ini...
observation, congested living conditions, small
6x8
8
exits, and difficult drainage and ventilation.
Sx8
10
Their construction is difficult and time consum-
8x10
11
ing. Exits may be blocked or shoring crushed
10x10
12
t10~~~xI~
123~
~
~NATURAL
10x12
13
GROUND LINE
12x12
14
SANDBAGS
12x12
14
OPENING
FOR
O BSERVATION
Construction Notes
1. Any combination of the four types of side panels
)
T45
cm iIART
COVERA
shown may be used in regard to location and number of
doors required.
2. In the construction of two or more basic units, the
2O3m MIN
LENG
exterior wall panels should be based on the number and
A
T
position of doorways required. Panels to be coupled in
.9
the interior of the shelter, forming a double wall, must
,
AUT
be of the same type wall construction and provide door-
AT
ways. Siding is not required on interior walls.
4.m
is
C. Cave Shelters. Caves are dug in deliberate
suMP
FOR
defensive positions, usually by tunneling into
SEAT FORRANAGE
OBSERVER
m
~ 3
hillsides, cliffs, cuts, or ridges, or excavating
OBSERVER
into flat ground. Because of the undisturbed
overhead cover, a cave is the least conspicuous
CROSS-SECTIONAL
VIEW
of all types of shelters if the entrance is cov-
(ENTRANCE
NOT SHOWN)
ered. One of the best locations for a supply
Figure 3-15. Observation post.
3-10
AGO
0016SA
FM 5-15
by a direct hit from a conventional weapon
ter which may be constructed in an emplace-
or ground shock from a nuclear explosion.
ment parapet. If it is necessary to construct
d. Special Use Shelters.
ammunition shelters above ground, particular-
(1) Observation posts. These are located
ly where the water level is close to the surface,
on terrain features offering as good a view as
a log crib built up with dirt is suitable.
possible of enemy-held areas (fig. 3-15). The
3-9. Heavy Overhead Cover
ideal observation post has at least one covered
To provide adequate protection against both
route of approach and cover as well as con-
penetration and detonation of artillery shells
cealment, while offering an unobstructed view
and bombs, a structure would require over-
of enemy-held ground.
head earth cover so thick as to be impracti-
(2) Command posts. Small unit command
cable. By combining materials and using them
posts may be located in woods, ravines, in the
in layers in a logical sequence, the required
basements of buildings, or former enemy for-
protection is provided with less excavation and
tifications. When none of these are available,
construction effort. Two designs of overhead
surface or cut-and-cover shelters previously
cover in functional layers which protect against
described may be modified for this purpose.
the penetration and explosion from a hit by a
LOG
155-mm artillery round are shown in figure
SUPPORT
3-17 and described below.
PARAPET$SAND
BAGS
a. Laminated Roof Construction. In this de-
sign either five 5 cm or seven 2.5 cm layers
DROP CURTAIN
of lumber are used for the laminated roof as
(TARPAULIN)
shown in 1, figure 3-17.
(1) Dustproof layer. Tar paper, canvas,
FLOOR
OF\E
LENT
or tarpaulins lapped and placed above the lam-
inated roof is used to prevent dust and dirt
from shaking down on equipment, weapons,
LOG
and personnel.
(2) Cushion layer. The cushion layer is
intended to absorb the shock of detonation or
LO\GS
penetration. Untamped earth is the best ma-
terial for this purpose and should be at least
30 cm thick. Materials such as loose gravel
SUMP
transmit excessive shock to the layer below
and should not be used in the cushion layer.
PERSPECTIVE
VIEW
This layer extends on all sides for a distance
Figure S-16. Ammunition shelter.
equal to the depth of the shelter floor below
(3) Medical aid stations. Cut-and-cover
the ground surface or a minimum of 1.5 me-
shelters are especially adaptable as aid sta-
ters.
tions since they are easily cleaned and venti-
(3) Waterproof layer. The waterproof
lated. Suitable sites may be found in pits,
layer is constructed of the same materials as
quarries, under banks, or in small buildings
the dustproof layer or similar materials. It is
or ruins.
intended to keep moisture from the cushion
(4) Ammunition shelters. Ammunition
layer in order to retain the cushioning effect
shelters should be located and constructed so
of the soft dry earth, and minimize the dead
that they protect ammunition against the
load the structure must carry.
weather and enemy fire. They should be well
(4) Burster layer. The burster layer is in-
concealed, and large enough to hold the desired
tended to cause detonation of the projectile
cuantity of ammunition close to the firing po-
before it can penetrate into the lower protec-
sition. Figure 3-16 shows an ammunition shel-
tive layers. This layer is made of 15- to 20-cm
AGO 20013A
3- 1
FM 5-15
AMOUFLAGELAYER
5cm
BURSTER LAYER
3cm
broken.
This layer
su
bals3
m30 c
DUSTPROOF LAYER~
s-~.'-c
LAY.LAMINATED
ROOF
5-5cm BOARDS
7- 2.5 cm BOARDS
-:
LAYERS EXTEND BEYOND
,EDGES OF SHELTER A
) LAMINATED
ROOF CONSTRUCTION -
thick. Irregular-shaped rocks are more effec-
b. Stringer Roof Construction. Figure 3-17,
tive for this purpose than flat rocks. If rocks
illustrates stringer roof construction of heavy
are not available, 20-cm logs may be used.
overhead cover. The construction is similar to
They must be wired tightly together in two
laminated roof construction with the addition
layers. The burster layer should extend on each
of-
side of the shelter a minimum of 1.5 meters.
(1) A lower cushion layer 30 cm thick
(5) Camouflage layer. The burster layer
on top of the dustproof layer. This layer of
is covered with about 5 cm of untamped earth
untamped earth does not extend beyond the
or sod, as a camouflage layer. A greater thick-
sides of the shelter.
3-12
AGO 2001SA
FM 5-15
5cm
//
.sL.4v~ ~ i
4iz~.JlliW.uw2
i04
r"'W
"'.
"'.CAMOUFLAGE.' LAYER
30cm
BURSTER LAYER
I~$
?"'Wk'n
-~~
+
~
..WATERPROOF
LAYER
30cm "'USHION
L
STRINGER ROOF CONSTRUCTION
Figure S-17-Continued.
(2) A distribution layer consisting 20-cm
c. Overhead Cover for Fighting Bunker.
timbers. This layer extends beyond each side
Figure 3-18 shows the details for the construc-
of the shelter a minimum of 1.5 meters and
tion of a fighting bunker with heavy overhead
rests on undisturbed earth to transmit part
cover. The material requirements for the con-
of the load of the top layers to the undisturbed
struction of this bunker are found in table 3-
earth on each side of the shelter.
3
3-10. Support of Overhead Cover
ENTRANCE
a. Overhead cover is normally supported on
the roof of the structure and the resultant load
.B-
G
od ~is
transmitted through the caps and posts to
the foundation on which the structure rests.
It may be necessary in some instances, to sup-
'.rl~~i
W-port
the roof directly on the earth outside a
M/f~js
$%\S
Mzrevetted
position. When this must be done, the
roof timber should not bear directly on the
FIRING PORT
earth outside the excavation. The added load
may cause the wall to buckle or cave in. In-
stead, the roof structure is carried on timber
Figure 3-18. Fighting bunker with heavy overhead
sills or foundation logs bedded uniformly in
cover.
the surface at a safe distance from the cut.
AGO 20013A
3-13
FM 5-15
w, 1 6
E E E
E E
.' u u
L
6----
.;
Il
; I
1
~3-14
ACO 2001
E
IO
o]3
co
0
I
I
I
FM 5-15
ECAMOUFLAGE LAYER
NOTE:
WALL TIMBERS ARE 15cm x 15cm
BURSTER LAYER
UNCOMPACTED SOIL LAYER
15cm (APPROX)
0
OVER HANG
INTERIOR VIEW
160cm (APPROX)
Figure 8-18-Continued.
5cm OF CAMOUFLAGE
30cm OF 15cm TO 18cm ROCK
DUST-PROOF LAYER
WATER-PROOF LAYER\
/30cm
OF UNCOMPACTED SOIL
SAND BAGYERS
5X30cm
BOARDS
25cm
..--
z-
'
DETAIL 'A'
E
FIRING PORT
ti1
N~ t
K
i
^
i
S
ENTRANCE
SECTION A-A
Figure J-18--Continued.
AGO 20013A
3-15
FM 5-15
Table 3-3. Bill of Materials, Fighting Bunker
No.
Nomenclature
Derscription
Quantities
1.
Roof ------
---
----------
5cm x 30cm x 2.11m-wood
48 pcs
5cm x 30cm x 4.54m-wood
14 pes
2.
Sidewalls
-
-----------
15cm x 15cm x 2.42m-wood
26 pcs
3.
Entrance wall
..-. .......
15cm x 15cm x 1.21m-wood
26 pcs
4.
Firing port & entrance door ......
15cm x 15cm x 30cm -wood
26 pcs
5.
Front & rear walls -........
15cm x 15cm x 1.51m-wood
13 peC
6.
Firing port & retaining wall ...
15cm x 15cm x 1.00m-wood
8 pcs
7.
Side post
.---
..-.
15cm x 15cm x 2.85m-wood
6 pcs
15cm x 15cm x 1.95m-wood
2 pcs
8.
Sandbags
.--
----
.
300 ea.
9.
Roofing paper
100 sq ft rolls
8 ea.
10.
Driftpins ---
-----------------
" x 12"
210 ea.
11.
Nails
...-
------------
16d
30 lb
This distance should be at least one-fourth the
(3) The roof designs shown here are not
depth of the cut and in no case less than 30
designed to be shellproof, even under a lam-
cm to the nearest edge of the sill. Round logs
inated earth and rock cover. The roofs shown
used for this purpose are embedded to at least
with the cover indicated are fragment proof
half their diameter to provide maximum bear-
and will give substantial radiation protection,
ing area of log to soil. These principles are il-
if properly designed entrances are provided.
lustrated in figure 3-19.
c. Sandbags are never used to support over-
DEPTH OF CUT-
(NEVER LESS THAN 30cm)
head cover.
Table 3-4. Thickness in Inches of Laminated Wood
'_ , -. ^}
IRequired
to Support Various Thicknesses of Earth
Cover over Various Spans
ROUND LOGS
(See Metric System conversion table, app B)
IMBEDDED
DEPTH OF
12 DIAMETER
Thicknesspa
width
in
feet
~~CUT ~of
earth
Span width in feet
cover in
,
___3_
feet
2½
3
31
4
5
6
1%
1
1
2
2
2
2
2
1
2
2
2
3
2½h
1
2
2
2
2
3
3
2
2
2
2
3
3
3h
2
2
2
2
2
3
3
4
2
2
2
2
3
4
Figure 3-1.9. Support of overhead cover on earth banks.
Table 3-5. Center to Center Spacing, in Inches, of
Wooden Stringers Required to Support a 1-inch Thick
b. Laminated planks or stringers are used
Wood Roof with Various Thicknesses of Earth Cover
to support the roof cover.
Over Various Spans
(1) Table 3-4 shows the thickness of lam-
(See Metric System conversion table, app B)
inated plank roof required to support various
thicknesses of earth cover. The planks should
Th
Spa
width i
feet
of earth
Span width in feet
extend from support to support in all layers,
ceetin
2%
3
3%
4
5
6
and adjoining edges should be staggered from
1½
40
30
22
16
10
18*
one layer to the next.
2
33
22
16
12
8/20'
14'
(2)
Table 3-5 shows the spacing of
2h
27
18
12
10
16'
10*
stringers required to support a one-inch plank
3
22
14
10
8/20*
14'
8'
3½
18
12
8/24*
18'
12'
8*
roof under various thicknesses of earth over
4
18
12 8/20
18*
12*
8*
various spans. Stringers are 2" x 4" unless
otherwise indicated.
Note. Stringers are 2" by 4" except th.,ose marked by an asterisk
(*) which are 2" by 6'.
3-16
AGO 2001SA
FM 5-15
3-11. Fighting Bunker with Light Overhead
tion can be obtained by building sandbag
Cover
walls. If sandbags are used inside the building
When establishing positions in wooded areas,
they reduce the useable space, but last longer
it is very important to provide overhead cover
and are not conspicuous. Care should be exer-
to protect personnel from the shrapnel of tree
cised in using sandbags above the first floor due
bursts. A fighting bunker with liglt overhead
to the weight involved.
cover is shown and described in figure 3-20.
(3) Window glass should be removed since
The overhead cover will stop fragments from
it gives no thermal protection and is danger-
tree and airburst artillery, and it is strong
ous when shattered. If it is retained as protec-
enough to withstand the effects of a direct hit
tion from the weather, it should be screened
by an 81-mm mortar. If the side openings are
or boarded.
closed with sandbags to prevent the entry of
(4) Several exits are necessary.
grenades, the fields of fire and observation are
(5) Provisions for fighting fire should be
limited to the front only. This is a serious dis-
made.
advantage with this type of position. Chicken
(6) Blackout arrangements should be
wire can be placed over the firing apertures
made, if not already provided by thermal
to prevent grenades from entering the bunker.
screening of doors and windows.
The chicken wire should be sloped with a ditch
c. Use of Weapons. In using a building as a
dug at the base to catch grenades as they roll
firing position, there are several considera-
off the wire.
tions.
3-12. Buildings as Shelters
(1) The preparatory work should not dis-
a. Protection. Some protection from enemy
close the intended use of the building to the
fire may be achieved for occupants in a build-
enemy.
ing used as a shelter by strengthening the
(2) Weapons must be sited well back from
building, by shoring up ceilings, and bracing
any opening so that neither weapons nor per-
walls. Men inside buildings are reasonably well
sonnel are visible from the outside.
protected against thermal effects and radiation
(3) Several firing positions should be
unless they are near doors or windows. The
available in order to obtain a wide field of
principal danger is from falling masonry and
fire. The shapes of the openings should not
from fire in the building.
be changed for this purpose.
b. Basic Consideration.
(4) Any openings other than the normal
(1) A ground floor or basement is more
ones are very conspicuous unless they are close
likely to make a suitable shelter than any other
to the ground.
floor. The risk
of being trapped
must
(5) There are no fixed designs for wea-
be guarded against. Heavy bars, pieces of pipe,
pons platforms under these circumstances.
or timbers should be available in each room
Platforms must be improvised from materials
that is occupied, for use by the occupants in
immediately available. Sandbags should be used
the event the building is demolished.
sparingly if there is any doubt about the
(2) Small arms fire will not penetrate the
strength of the floor.
walls if they are 45 cm (18 in.) thick. The
d. Utilization of Buildings. Utilization of
walls will not usually splinter from small arms
existing buildings as shelters is discussed in
fire if they are 30 cm thick. Additional protec-
detail in TM 5-311.
AGO 20013A
3-17
FM 5-15
CHICKEN WIRE FOR
_
- GRENADE PROTECTION
GRENADE
-S ID
i
<~SIDE
LOOSE EARTH
...
-
CUSHION
a-m'
_
-1
15 CM(BURSTER
LAYER
LAYER)
20CM
30CM---}_~
30CM
SECTION
FRONT
Figure 3-20. Fighting bunker with light overhead cover.
3-18
AGO 20013A
FM 5-15
CHAPTER 4
TRENCHES AND FIELDWORKS
Section I. TRENCHES
4-1. Purpose
about 60 cm wide. This trench is the narrowest
a. Defensive Area. Trenches are excavated
practicable for most purposes and of the least
as fighting positions and to connect individual
width that can be dug without difficulty. It
foxholes, weapons emplacements, and shelters
should be zigzagged or winding. The spoil is
in the progressive development of a defensive
thrown up onto parapets, normally on each
area. They provide protection and concealment
side of the trench. If the trench runs across
for personnel moving between fighting posi-
a forward slope, it is better to throw all the
tions or in and out of the area. Trenches should
spoil on the enemy side to make a higher
be included in the overall layout plan for the de-
parapet.
fense of a position. The excavation of trenches
b. Fighting Trench. In developing a trench
involves considerable time, effort, and materials
system the outline of the trench is marked out
and is only justified when an area will be oc-
on the ground if time permits; if the digging
cupied for an extended period. Trenches are us-
is to be done at night, the ground is taped.
ually open excavations but sections may be cov-
ered to provide additional protection if the
30RM
ELBOW REST
overhead cover does not interfere with the fire
FRONT
PET
mission of the occupying personnel. Trenches
0cm
are difficult to camouflage and are easily de-
--
I
a
tected, especially from the air.
b. Development. Trenches are developed pro-
60cm
90cm
gressively as is the case for other fighting po-
.
sitions. As they are improved they are dug
deeper, from a minimum of 60 cm to approxi-
(i
ISt STEP
mately 1.7 meters. As a general rule, there is
a tendency to excavate deeper for other than
fighting trenches to provide more protection or
30cm
45cm
to allow more headroom. Some trenches may
/_
also have to be widened to accommodate more
traffic including stretchers. It is usually neces-
,
sary to revet trenches that are more than 1.5
REAR
-
AMUNITION
meters deep in any type of soil. In the deeper
PARAPET
RECESS
trenches some engineer advice or assistance
135cm
may be necessary in providing adequate drain-
age.
4-2. Construction
a. Crawl Trench. The crawl trench is used
I
to conceal movement into or within a position
(
2 d STEP
and to provide a minimum of protection.
Crawl trenches should be 60 to 75 cm deep and
Figure 4-1. Development of a fighting trench.
AGO 20018A
4-1
FM 5-15
The berm line is indicated about 45 cm from
(4) Rear parapet. The rear parapet is
the front edge of the trench. The trench is dug
made of spoil that is not required for the front
by men working in the same direction (not
parapet. If the spoil is available the rear para-
facing each other or back to back), and far
pet should be higher than the front parapet
enough apart so that they do not interfere
to prevent silhouetting of soldiers' heads when
with each other.
firing. The rear parapet may be up to 45 cm
(1) First step. The trench is dug to a
high and should be at least 45 cm wide at the
depth of 90 cm (3 ft.) below ground level (1,
top, sloped steeply in front. Parapets may be
fig. 4-1). At this point both men are able to
omitted to aid concealment or when ground
fire in either direction, in a kneeling or crouch-
provides background and protection to the
ing position. In ordinary soil this step can be
firer's rear.
completed in approximately 2 hours. The sides
(5) Concealment. Parapets are finished off
of the trench are kept vertical, or as steep as
by replacing turf or topsoil. The trench and
possible. If the soil is not stable, the sides
parapets are covered with any available camou-
require revetting immediately. Spoil is thrown
flage material, arranged to permit firing.
to each side of the trench in alternate shovel-
(6) Drainage. A sump is dug at the lowest
fuls beyond the berm lines until each parapet
point to prevent the floor of the trench from
is about 30 cm high and at least 45 cm wide on
becoming wet and muddy.
the back parapet. The remaining spoil is
c. Standard Trench. The standard trench is
thrown on the front parapet until it is at least
developed from the fighting trench by lowering
150 cm wide (fig. 4-1).
it to a depth of 1.7 meters (51/. ft.) It may be
(2) Second step. The second step consists
constructed with fighting bay (fig. 4-2) or
of deepening the trench until it is approxi-
with a fighting step (fig. 4-3). Fighting posi-
mately 135 cm deep from the level of the
tions are constructed on both sides of the
trench parapet (2, fig. 4-1). Normally, the
trench to provide alternate positions to fight
front parapets are 30 cm high and the dirt
to the rear, to provide step off areas for foot
settles 5 to 10 cm. Parapets are then shaped
traffic in the trench, and to provide protection
and camouflaged.
against enfilade fire. This trench provides more
(3) Front parapet. The front parapet
protection than the fighting trench due to its
must be made according to the lay of the
depth. Additional protection in the form of
ground and the requirements of the weapon.
A front parapet is often unnecessary on a
FIGHTING BiY
steep forward slope. At most sites a front para-
WIDTH-DEPTH-90Cm
pet improves the field of fire and should be
constructed as follows:
(a) Height. A convenient height for the
'
*,
front parapet for firing purposes is 23 to 30 cm
when the ground is level. It should be higher to
fire uphill and the crest should be irregular to
.
- -
aid concealment. The height shown in figure
4-1 is average.
(b) Width. A reasonably bulletproof
parapet should be 1 meter in width. Since it
is sloped in front and rear, the total width on
;
' "
the bottom will be approximately 2 meters.
\
(c) Berms. The berm on the front of
,/
the trench forms an elbow rest which is usually
about 45 cm wide. If an M60 machinegun on a
I60'
bipod is to be fired, the firing platform should
be 90 cm from front to rear.
Figure 4-2. Standard trench with fighting bay.
4-2
AGO 20013A
FM 5-15
9 0cm
30
60cm
125cm -
3 0 r
e 90cmt
PARAPET
ELW'*
:4ti;04
~
;24
l -
1
STAGGERED
· _-~?~"ci
FIRE POSITIONS
ELBOWm 4:
RESTC~
~
\EI
mBOTH
SIDES
[1* --
6
0c 3
P AnEi
30
cm
ELBOW RES
D
GCM
Figure 4-3. Standard trench.
overhead cover may also be provided. This
described below to simplify construction. Spe-
trench is primarily a fighting position but it
cial combinations and modifications may be
can also be used for communications, supply,
developed.
evacuation, and troop movements.
(1) Octagonal trace. The octagonal trace
d. Traces. Each trench is constructed to the
(1, fig. 4-4) is excellent for fighting trenches
length required and follows one of the traces
AGO 20013A
43
A(Oo 20013A
4--
FM 5-15
t f-
LGENERAL
LINE
(C)
It facilitates oblique fire along the
PAC
ES|ACES
OF TRACE
front.
--
-[-- -- r- -
-~ _
_(d)
It is economical to construct, both
\ l | -
r -
- -
in labor and material.
6 PACES
(e) It can be provided with a continu-
ous fire step. Its chief disadvantage is that its
layout lacks simplicity of detail.
@ OCTAGONAL TRACE
(2) Zigzag trace. The zigzag trace (2,
fig. 4-4) can provide protection from enfilade
fire and shell bursts by the employment of
short tangents and by the occupation of al-
·5
_
ACES
|-~
GENERAL LINE
ternate tangents. The zigzag trace has the fol-
OF
TRACE
lowing advantages:
(a) It is the simplest and easiest to
6 PACES
trace, construct, revet, and maintain.
(b) It may be readily adapted to the
terrain.
(c) It permits both frontal and flank-
(
ZIGZAG
TRACE
ing fire. This trace has no specific disadvan-
tages.
Figure 4-4. Standard trench traces.
e. Trench Boards. If the sumps are choked
[41·...- I.6"-.
" X 2" OR I" X 4"
with mud, they will cease to function. When
this happens, alternatives include some forms
2"
X
4"°OFFSETo,,
_
of flooring. Trench boards (fig. 4-5) are the
2" X 4"
OFFSET OF
STRINGERS
most practical. Timber planks, metal mats, or
CROSS SECTION
PROVIDES FOR
OVERLAP AT
saplings wired together may also be used.
JOINT
4-3. Drainage
OUTER EDGE OF CROSS PIECES
a. Siting. Emplacements,
shelters,
and
4' FROM END OF STRINGERS
I
2
OR I" X4"
trenches are sited to take advantage of the
1 6'-6"
natural drainage pattern of the ground. They
are constructed so as to provide for-
.... 4_,--,x
..
.
.
(1) Exclusion of surface runoff.
:r--
I
I ',OVERLAP : -i
(2) Disposal of direct rainfall or seepage.
SIDE
ELEVATION
(3)
Bypassing or rerouting natural drain-
age channels if they are intersected by the
emplacement or shelter.
12"
'
x4"
SIDE
ELEVATION
END
ELEVATION
OF SUPPORT
OF SUPPORT
Figure 4-5. Trench board and support.
in most situations. The octagonal trace has the
following advantages:
(a) It affords easy communication.
\
NCH
(b) It
affords
excellent
protection
against enfilade fire.
Figure 4-6. Siting to lessen problem of runoff disposal.
4-4
AGO 20013A
FM 5-15
4-11. When permitted by the tactical situation,
WOODEN FLUME
excavation of trenches should commence at the
flh
\
A
_lowest
level and progress upward in order to
avoid collecting water in the bottom of a par-
tially completed trench. The central collecting
points may be either natural drainage lines or
sumps below the bottom of the excavation as
shown in figure 4-9. Such sumps are located
at points where the water will percolate
Figure 4-7. Use of open flume to direct water
through permeable
soil or can be
piped,
across ditch.
pumped, or bailed out.
Figure 4-8. Use of undertrench drains.
:
;, .
b. Surface Runoff. Proper siting, as illus-
-*-
.
'
trated in figure 4-6, can lessen this problem
,.
'
:'
by locating the emplacement, shelter, or trench
in an area not subject to excessive runoff.
Figure 4-9. Drainage sump in bottom of excavation.
Surface water may be excluded by excavating
interceptor ditches upslope from the emplace-
4-4. Overhead Cover
ment or shelter. It is much easier to prevent
a. Light Cover. Expedient overhead cover
surface water from flowing in than to remove
may be supported as shown in figure 4-10.
it after it is in the excavation. Fortifications
Logs 15 to 20 cm in diameter should be used to
should be sited so as to direct the water to
support light earth cover. Saplings laid in a
natural drainage lines. If this is not possible,
laminated pattern to a depth of 15 to 20 cm
the water is conducted across the trench
may be used as a substitute for the logs. The
through open flumes developed for the purpose
total thickness of the logs or saplings and the
or under the trench using a combination of
earth cover should be a minimum of 45 cm.
trench drains and culverts. An application of
the open flume method for use with trenches
r
is shown in figure 4-7. A typical undertrench
45cm
EARTH
COVER
drain is shown in figure 4-8.
/..
c. Direct Rainfall or Seepage. Water collect-
\,,
ing within an emplacement or shelter is car-
23.
..
4
ried to central points by providing longitudinal
\6
e
,r
slopes in the bottom of the excavation. A very
gradual slope of 1 percent is desirable. In
trenches the slope is best provided for by fit-
ting the trench to the terrain in such a way
that the original surface has a moderate slope,
as shown on the contoured layout in figure
Figure 4-10. Rivetted fighting trench with cover.
AGO 20013A
4-5
FM 5-15
,
z~~~~~~
w~~~~~~~~~~~~~~~~~~~~~~
LL~~~~~~~~~~o
V
0
W~~~~~~~~~~~~~~~~~~~~~
/
''
_LLO
W
[TW
F-
LL~~~~~~~~~~~~~~~~~~~-
-- W 0
4-6
AGO
20013A
w
L
wu~~~
o
Er
,
:zi 0 14
W Z
w
I:
-
X F- r
_j
0
-LL
cn2~~~~ns
fo
0
Cf
4-6
AGO 20013Azr
FM 5-15
b. Heavy Cover. If heavy overhead cover is
used in the construction of trenches it should
be installed in 6- to 12-meter sections and in
conjunction with the overhead cover of em-
placements
and shelters connected by the
trenches. Support for heavy overhead cover is
provided by post-cap-stringer type structures
as shown in figures 4-12 and 4-13. Trenches
must be widened and deepened to accommodate
these structures in accordance with informa-
tion contained in the above illustrations. Bills
of materials are shown in tables 4-1 and 4-2.
4-5. Revetment
a. Wall Sloping. The necessity for revetment
may sometimes be avoided or postponed by
sloping the walls of the excavation. In most
soils a slope of 1:3 or 1:4 is sufficient. This
method may have to be used temporarily if the
TYPICAL TRENCH COVER SECTION
soil is loose and no revetting materials are
X
ONE SECTION
available. However, wall sloping can seriously
reduce the protection due to the increased
3
TWO SECTIONS
width of the trench at ground level. In any
i
i THREE SECTIONS
case where wall sloping is used, the walls
should be dug vertical first and then sloped.
W
FOUR SECTIONS
Multiply the height of the wall as in figure 4-14
FIVE SECTIONS
by the slope to be used 1:4 (1/4). This gives
USE CROSS BRACING ON ALL END SECTIONS.
the amount the wall must be cut back at
MORE THAN FIVE SECTIONS USED (9m
OR GREATER)
CROSS BRACE CENTER SECTION.
ground level. Then, cut out a section about 30
cm wide for a guide, as shown.
Figure 4-12. Trench cover section, dimensioned timber.
t5~10r
4)
(
3
3
TOP VIEW
TOP VIEW
LINE
3-INCH
/
B'////
OF TRENCH
6'-I"
II 4"
LEFT SIDE
FRONT
LEFT SIDE
FRONT
FRAME
WITH ROOF
FRAMING
DETAILS
Figure 4-12-Continued.
AGO 20013A
4-7
FM 5-15
Table 4-1. Bill of Materials, Trench Cover Section, Post, Cap, and Stringer Construction Dimensioned Timber
(fig. 4-12)
(See Metric System conversion table, app B)
Addi-
Basic
tional
section
sections
No.
Nomenclature
Size
as
when
shown
used
in
series
I
Post -......
8" x 8" x 7'4"
4
2
2
Cap ------- -- --- ------..
......
.
. -
8" x 10" x 6'2"
2
2
3
Footing
2" x 8" x 1'4"
16
8
4
Top spreader -...........................
3" x 8" x 3'6"
2
1
5
Bottom spreader -.................
.
..
3" x 8" x 4'0"
2
1
6
Scab
3" x 8" x 2'0"
4
2
7
Stringer-* -----------------------.....
6" x 8" x 5'10"
13
13
8
Bracing -...............................
3" x 8" x 9'6"
2**
2**
9
Driftpin -3
" x 16"
8
4
10
Driftpin
%" x 12"
26
24
11
Nails ..-...................
60d
20 lb
15 lb
* Laminated wood roof, designed in accordance with table 3-4 may be substituted if desired.
*- Change to 4 when cross bracing is required. See bracing details
Suggested Construction Procedure
1. Dig holes for footers.
2. Place footers in holes making them as level as possible.
3. Nail posts to footers.
4. Place caps on top of posts and secure with driftpins (bore one-half-inch holes for pins).
5. Nail scabs in place.
6. Nail top and bottom spreaders in place.
7. Nail side braces in place.
8. Put stringers on top of caps and secure with one-half-inch driftpins.
9. Use typical overhead cover.
Table 4-2. Bill of Materials, Trench Cover Section, Post, Cap, and Stringer, Construction Log (fig. 4-13)
(See Metric System conversion table, app B)
Addi-
Basic
tional
sction
tions
No.
Nomenclature
Size
as
when
shown
used
series
1
Post ------------------------
12" log x 7'4"
4
2
2
Cap .-.-..........
12" log x 7'6"-
2
2
3
Sill -......
12" log x 6'4"
2
1
4
Stringer*** .
.-.......................
10" log x 6'4"
8
8
5
Scab .-.
3" x 8" x 1'6"**
4
2
6
Bracing
6" log x 9'6"
4
4
7
Top spreader
..-...
6" log x 3'6"
2
1
8
Driftpins -'
" x 16
46
34
9
Nails
...-....
....
60d
201b
18 lb
* Or larger multiple thereof.
*- Scab should be dimension timber as indicated, whenever such material is available. When only logs are available the scab should be split
out of the center of an 8" log.
** Laminated wood roof, designed in accordance with table 3-4, may be substituted if desired.
Construction Notes
1. Dig trenches for sills.
2. Place sills and level up.
3. Fasten posts to sills with one-half-inch driftpins.
AGO 20013A
FM 5-15
4. Place caps on posts, secure with driftpins.
5. Nail scabs in place.
6. Nail in top spreaders.
7. Nail cross bracing in place.
8. Place stringers on top of caps and secure with one-half-inch driftpins.
9. Use typical overhead cover.
USE DOUBLE SCAB WITH
WHERE POSSIBLE USE
6'-8
NONCONTINUOU
CAP
CONTINUOUS CAP
-4
40
'- "
IFOOTING
SILL DETAIL
DRILL HOLES FOR
DRIFT
PINS
BOTH LOGS OF THE
TOP VIEW (FOOTERS
OMITTED)
CROSS BRACING IDENTICALLY
(Si)~~~~~~~~~~~~~
~NOTCHED
7'6"
'-61
CUT ALONG LINES
~~(DI<>~~~~~ ~SCAB
DETAIL
CROSS BRACING DETAIL
-O'
t
B '-2..
FLOOR
NOTCH STRINGER /
AND FLATTEN CAP 1/2
THRU-OUT LENGTH
)
TYPICAL TRENCH COVER
SECTION IS 7'-6" FROM
CENTER
TO CENTER
OF POSTS
ISOMETRIC
VIEW
END
VIEW
Figure 4-13. Trench section, log construction.
b. Facing Type Revetment. Facing revet-
Figure 4-13-Continued.
ment serves mainly to protect revetted surfaces
(1) Materials for facing. The facing may
from the effects of weather and damage caused
be constructed of brushwood hurdles, continu-
by occupation. It is used when soils are stable
ous brush, pole and dimensioned timbers, cor-
enough to sustain their own weight. This
rugated metal, or burlap and chicken wire. The
revetment (fig. 4-15) consists of the revetting
method of constructing each type is described
or facing material and the supports which hold
below.
the revetting material in place. The facing
(2) Methods of support. The facing may
material may be much thinner than that used
be supported by-
in a retaining wall. For this reason facing type
(a) Timber frames. Frames of dimen-
revetments are preferable since less excavation
sioned timber are constructed to fit the bottom
is required. The top of the facing should be set
and sides of the position, and hold the facing
below ground level so that the revetting is not
material apart over the excavated width.
damaged by tanks crossing the emplacement.
AGO 20013A
4-9
FM 5-15
FACING
PCKET
-
SLOPE 1:4
90cm
BRACE
Figure 4-14. Method of sloping earth walls.
KES OR
HOLDFASTS
FACING
PICKETFACING
Figure 4-16. Facing revetment supported by pickets.
STAKES OR HOLDFASTS
PLACED HERE AS IN
FIGURE 4-16
:
If
ground on the position side of the facing ma-
5.
...
(3) FaciIg type revetments. Facing type
-- 01-./.
..
stakes
driven into
the ground and tiebacks.
<Hi
EQUAL TO H+2'
(3) Font
tion se
of te facing type
rsci
MyN
revetments may be supported either by timber
Figure 4-17. Method of anchoring pickets.
4sho
i
Figr 41
byraAGO
200 3A
FM 5-15
frames or pickets. The size of pickets required,
and their spacing, are determined by the soil
and the type of facing material used. Wooden
"'
.....
pickets should not be smaller than 7.5 cm in
diameter or in the smallest dimension. The
maximum spacing between pickets should be-
about 2 meters. The standard pickets used to
support barbed wire entanglements are excel-
I
.-
lent for use in revetting. Pickets are driven at
least 45 cm into the floor of the position. Where
.
t
the tops of the pickets are to be anchored, an
a
anchor stake or holdfast is driven into the top
SPACING
of the bank opposite each picket and the top
\
of the picket is racked to it as shown in figure
APPROX
4-17. The distance between the anchor stake
'\ \
0
IOcm
and the facing is at least equal to the height
of the revetted face, with alternate anchors
staggered and at least 60 cm farther back.
Several strands of wire holding the pickets
against
the
emplacement
walls
must
be
Figure 4-19. Continuous brush revetment.
straight and taut. A groove or channel is cut
in the parapet to pass the wire through.
pickets are driven in place and the tops of the
_pickets are tied back to stakes or holdfasts.
The ends of the hurdles are then wired together.
d. Continuous Brush. As shown in figure
4-19, a continuous brush revetment is con-
structed in place. Sharpened pickets, 7.5 cm
'A /lw1~~~
[.,iTin
diameter, are driven into the bottom of the
trench at 1-pace intervals and about 10 cm
from the earth face to be revetted. The space
behind the pickets
is packed
with small
straight brushwood laid horizontally and the
tops of the pickets are anchored to stakes or
holdfasts.
e. Pole and Dimensioned Timber. A pole
revetment (fig. 4-20) is similar to the continu-
ous brush revetment except that a layer of
50 cm
|
small horizontal round poles, cut to the length
r
of the wall to be revetted, is used instead of
1 ·-
n
2|.
brushwood. Instead of poles, boards or planks
are used if available; they have the added ad-
vantage of being more quickly installed. Pick-
c. Brushwood Hurdle. A brushwood hurdle
ets are held in place by holdfasts or struts.
is a woven revetment unit usually 2 meters
f. Metal. A revetment of corrugated metal
long and of the required height. As shown in
sheets, (1, fig. 4-21) or pierced steel plank
figure 4-18, pieces of brushwood about 2.5 cm
may be installed rapidly and is strong and
in diameter are woven on a framework of
durable. It is well adapted to emplacement
sharpened pickets driven into the ground at
construction because the edges and ends of
50 cm intervals. When completed, the 2-meter
sheets or planks can be lapped as required to
lengths are carried to the position, where the
AGO 20013A
4-11
FM 5-15
PARAPET
STRUTS
Figure 4-20. Timber revetment using small poles.
-GOe
QBURLAP
AND CHICKEN WIRE
..
gure
,-~0·
''
mber revet
tFigure
4-21-Continued.
.'-.
*-
.
:
,
4-6. Repair and Maintenance of Trenches
....
it.11>1
*z/X.t
·:.
a. Maintenance.
....
A: 1ta
)
;(1)
Drainage. It is important to keep the
drainage working properly. If water is allowed
to stand in the bottom of a trench, the revet-
ment will eventually be undermined and be-
come useless. Sumps and drains must be kept
; . '
clear of silt and refuse. Trench boards should
id t~'~J'
.,'~
['X:''
be lifted periodically so that the mud can be
cleaned out from beneath them.
~i-'-- l
~
\
~
! ~:
/(2)
Berms. Berms must be kept clear and
of sufficient width to prevent soil from the
parapets falling into the trench.
: } ,1'
/2 CORRUGATED
SHEETS
,(3)
Revetted trenches. When wire and
,/"/.'CORRUGATE
.S
pickets are used to support revetment material;
the pickets may become loose, especially after
Figure 4-21. Type8 of metal revetment.
rain. Improvised braces may be wedged across
the trench at or near floor level, between two
produce a revetment of a given height and
opposite pickets. Anchor wires may be tight-
length. All metal surfaces must be smeared
ened by further twisting. Anchor pickets may
with mud to eliminate possible reflection of
have to be driven in further to hold the tight-
thermal radiation and to aid in camouflage.
ened wires.
Burlap and chicken wire revetments are in-
(4) Sandbag revetments. Periodic inspec-
stalled as shown in 2, figure 4-21. When dam-
tions must be made of sandbags. Any bags
aged, corrugated metal forms dangerous sharp
that are split or damaged should be replaced.
edges. Prompt attention should be given to the
b. Repair.
repair of damaged revetments to prevent in-
(1) Top of trench. If the walls are crum-
juries to personnel or damage to equipment.
bling at the top, making the trench wider at
4-12
AGO 20013A
FM 5-15
SANDBAGS
BEFORE REPPA
FTER
REPAIR
TRENCH DAMAGE AT GROUND LEVEL
2.5cm PLANK
SHORT PICKET
BEFORE REPAIR
AFTER REPAIR
2 DAMAGE NEAR FLOOR LEVEL
Figure 4-22. Trench repair,
ground level, an elbow rest should be cut out
between the planks at floor level. Earth is
of the full width of the berm and about 30 cm
placed in back of the planks.
deep, or until firm soil is reached. Sandbags or
sods are then used to build up the damaged
(3) Collapsed wall. If an entire wall ap-
area (1, fig. 4-22).
pears to be collapsing, the trench must be
(2) Bottom of trench. If the trench walls
completely revetted (para 4-5) or the walls
are wearing away at the bottom, place a plank
sloped (fig. 4-14) so they will stand. If the
on edge, or shift brushwood as shown in 2,
walls are permitted to cave in, the trench usu-
figure 4-22. The plank is held against the trench
ally must be widened at ground level which
wall with short pickets driven into the trench
reduces its protective value. Cave-ins should be
floor. If planks are used on both sides of the
prevented as far as possible by revetting the
trench, they are held in position with a piece
trench in time or by one of the remedial meas-
of timber cut to the right length and wedged
ures described above.
AGO 20018A
4-13
FM 5-15
Section II. FIELDWORKS
4-7. Revetments
cal face. The face must have a slope of 1:4
a. Use of sandbags. Walls are built of sand-
and the base must be on firm ground and dug
bags or sod in much the same way as bricks are
at a slope of 4:1. The sandbag wall should lean
used. Sandbags are also useful for temporary
against the earth if it is to hold in place (fig.
retaining wall
type revetments, especially
4-23).
where silent installation is essential. The two
types of sandbags in use are the cotton osna-
burg and the polypropylene. Both are used in
the same manner but the polypropylene bag
will last approximately seven months, twice as
long as the cotton osnaburg bag. Sandbags used
in revetments rot in damp weather and fade
in the sunlight. The useful life of sandbags can
be prolonged by filling them with a mixture of
dry earth and portland cement, normally in
t
the ratio of 1 part of cement to 10 parts of dry
earth. The cement sets as the bags take on
moisture. A ratio of 1 to 6 should be used for
a sand-gravel mixture. The filled bags may be
dipped in a cement-water slurry as an alterna-
Figure 4-24. Use of combat intrencher to fill sandbags.
tive method.
(a) The bags are uniformly filled about
HEADERS
three-fourths full with earth or with a dry
STRETCHERS
soil-cement mixture and the choke cords are
tied.
d.
(b) The bottom corners of the bags are
tucked in after filling.
SECTION
ELEVATION
SECTION
ELEVATION
(C) As the revetment is built, the re-
CHOKES AND SIDE SEAMS OUT
CHOKES AND SIDE SEAMS IN
vetted face is made to conform to this slope by
backfilling or additional excavation.
(d) Sandbags are laid so that the planes
between the layers have the same pitch as the
foundation, i:e., at right angles to the slope
ELEVIATON
ELEVATION
I
of the revetment.
JOINTS NOT BROKEN
JOINTS BROKEN
(e) The bottom row of the revetment
(WRONG)
(RIGHT)
is constructed with all bags placed as headers
(fig. 4-23). The wall is then constructed using
alternate rows of stretchers and headers with
the joints broken between courses. The top
row of the revetment wall consists of headers.
SECTION
ELEVATION
SECTION
ELEVATION
(f)
All bags are placed so that side
(WRONG)
(RIGHT)
(WL
STRETCHEROG
(TRETCHERIGnND
HT) DES
seams on stretchers and choked ends on head-
ers are turned toward the revetted face.
Figure 4-23. Retaining wall revetment.
(2) Common faults. The common faults in
sandbag revetments are illustrated in figure
(1) Construction. As a rule sandbags are
4-23. Sandbags rot quickly, especially in wet
used for revetting only when the soil is very
climates. Consequently, considerable mainte-
loose and requires a retaining wall to support
nance is required.
it and for the repair of damaged trenches. A
(3) Expedient means of filling sandbags.
sandbag revetment will not stand with a verti-
Often the requirement for filled sandbags far
4-14
AGO 20013A
FM 5-15
ients include earth-filled packing cases or am-
are placed in position and nailed to the lids
of the layer below; the boxes are filled with
.
YX.
:d7
m
earth or rock and the lids fastened in place.
aPlywod
This procedure is repeated for each row. The
tops of the revetments are tied to pickets to
prevent overturning.
4-8. Breastworks
Breastworks may be substituted for trenches,
weapons emplacements, etc., when soil condi-
tions or a high water table makes excavation
Figure 4-25. Expedient funnel for filling sandbags.
to the required depth impossible. Under these
circumstances earth must be built up above
exceeds the capabilities of men using shovels
ground level to form protective walls
This
ground level to form protective walls. This
to fill sandbags. A high speed combat intrench-
to fill sandbags. A high speed combat intrench-
work requires more time and effort than digging
ing machine can be used to fill sandbags if local
trenches of comparable depth. Breastwork de-
trenches of comparable depth. Breastwork de-
soil is to be used as the filler. The bag is filled
fenses are not as good protection against air-
by holding it under the discharge conveyor as
bursts as excavated positions. They also have
the intrenching machine is run forward at a
slow speed (fig. 4-24). This method will pro-
I meter--
duce filled sandbags at a rate of one every four
I ON 4
to five seconds. The spillage can be used to fill
BATT N
sandbags also since it is often loose and easily
GROUND
shoveled. If the sandbags are to be filled from
LINE
...........
a stockpile of sand or other material, the work
0 SANDBAG BREASTWORK
can be made easier and the bags filled faster
meer
ENEMY
by using the funnel as shown in figure 4-25.
I
The funnel can be constructed using either
I ON 4
lumber or steel.
BATTER
GROUND
b. Sod Blocks. Thick sod with good root
LINE
systems provides a satisfactory revetting ma-
terial. Sod blocks cut into sections about 23
by 46 cm are laid flat, using the alternate
mr
ENEMY
stretcher-header method described above forNEMY
use with sandbags. Sod is laid grass-to-grass
ION 2 SLOPE
and soil-to-soil, except for the top layer which
nAK STICK
GROUND
should be laid with the grass upward, to pro-
vide natural camouflage. As each layer of sod
MN. DIAMETER LOG POST
is completed, wooden pegs are driven through
LOG FENCE AND EARTH BREASTWORK
the layers to prevent sliding until the roots
ROUND OR SQUARED TIMBER
grow from layer to layer. Two pegs are driven
through each 23 by 46 cm sod. Sod revetment
PLANKS OR
,
COPACTED SNOW
is laid at a slope of about 1 horizontal to 3
ROUND
vertical.
TIMBER
c. Expedients. In cold weather blocks of ice
PLANKl.\.
may be used to construct retaining wall type
INTERVAL BETWEEN TRESTLES
1.5-2 me1er
revetments. They are stacked in the same man-
OG AND SNOW BREASTWORK
ner as sandbags or sod. Water is applied to
bind them together by freezing. Other exped-
Figure 4-26. Varied types of breastworks.
AGO 20013A
4-15
FM 5-15
serious disadvantages against blast and nu-
c. Equipment. When large cleared areas are
clear radiation.
necessary bulldozers with winches or dozers
a. Construction. When breastworks are con-
with land clearing blades are required for
structed for fire positions and weapons em-
grubbing trees. Bulldozers can clear from
placements their dimensions should conform
10,000 to 12,000 square meters of heavy jungle
to excavated positions. A front breastwork
in 8 hours. Dozers with land clearing blades
should be bulletproof, i.e., of approximately 1
can clear 15,000 to 25,000 square meters of
meter minimum thickness. The outer face
heavy jungle in the same length of time.
should be sloped gently; not steeper than 1:2
d. Drainage. Good drainage is required for
(fig. 4-26). The inner face should be sloped
all excavations and should be considered in the
1:4 and revetted. A rear breastwork may be
initial siting of the position. Trenches, shel-
similar to the front.
ters, and emplacements are floored as soon as
b. Snow Breastworks. Snow breastworks
possible. Stone, or brushwood covered with
can be constructed as shown in 4, figure 4-
bamboo matting may be used.
26.
4-9. Snow Defenses
a. Snow as Protective Material. Snow must
be packed to be effective against small arms
7r///
fire. Drifted snow is usually well compacted by
45Cm
the wind. Loose snow has only about half the
BRUSRWOOD LAIO
value of packed snow in resisting penetra-
tion but shells and grenades bursting on im-
pact are largely ineffective in loose snow be-
DUMY TRENCH
cause the fragmentation is blanketed. The
thickness of snow required for protection
against small arms and shell splinters is as
BOX WITH OPEN END
TO THE FRONT
follows:
Newly fallen snow ..
At least 4 meters
Firmly frozen snow
At least 2.5-3 meters
Packed snow
At least 2 meters
Ice_
._
At least 30 cm
b. Trenches. In deep snow, trenches and
weapons emplacements may be excavated inUMY
MBRSUR
the snow to approximately normal dimensions.
Figure 4-27. Dummy earthworks.
Unless the snow is well packed and frozen,
e. Overhead Cover. Waterproof material
revetment will be required (4, fig. 4-26). In
such as building paper should be included in
shallow snow, not deep enough to permit ex-
the overhead cover for shelters or trenches
cavation to the required depth, snow breast-
and should overlap the sides of the structure
works must be constructed. These should be of
about 60 cm. Material used as overhead cover
compacted snow, at least 2 meters thick, and
must be well supported and sloped so that water
revetted.
will run off.
4-10. Defenses in Tropical Conditions
4-11. Dummy Earthworks
a. Advantages.
a. Dummy Trenches. Dummy trenches are
(1) Concealment is comparatively easy.
dug so as to conceal from the air or ground the
(2) Timber is readily available.
true extent of a defended area or locality.
b. Tools. A variety of cutting tools are re-
Dummy trenches should be dug about 45 cm
quired to-
deep, with brushwood laid in the bottom (1,
(1)
Clear fields of fire.
fig. 4-27). The brushwood has the effect of
(2) Cut tree roots during excavation.
producing an internal shadow similar to that
(3) Cut timber for overhead cover.
cast by a deep trench. Parapets must be simi-
4-16
AGO 2001A
FM 5-15
lar to those of other trenches in the position.
will soon collapse. Therefore, construction of
False parapets should also be concealed.
tunneled defenses is usually limited to-
b. Dummy Emplacements. The most notic-
(1) Hilly terrain-steep hillsides.
able feature of a roofed emplacement is the deep
(2) Favorable soil, including hard chalk,
internal shadow of its embrasure. This appears
soft sandstone, and other types of hard soil
to the enemy from the ground as a black patch
or soft rock.
of regular shape. Usually, it will appear rect-
c. Tunnel Examples. A sketch of tunnels
angular if the roof is flat. A rectangular em-
constructed in Korea is shown in figure 4-28.
brasure can be simulated by means of a box
The soil was generally very hard and only
placed in the ground, with open end to the
the entrances were timbered. The speed of ex-
front, and covered with earth (2, fig. 4-27).
cavation, using handtools, varied according to
Some attempt at concealment and occasional
the soil, seldom exceeding 7.5 meters per day.
signs of occupation will add realism.
In patches of hard rock, as little as 1 meter
was excavated in a day (24 hours). The use of
4-12. Tunneled Defenses
powertools did not alter the speed of excava-
a. Considerations. Tunnels are not used fre-
tion significantly. The work was done by en-
quently in the defense of an area due to the
gineer units assisted by infantry personnel.
time, effort, and technicalities involved; how-
d. Construction. Tunnels of the type shown
ever, they have been used to good advantage.
(fig. 2-48) are excavated about 9 meters (30
Tunneled defenses can be used when the length
ft.) below ground level. They may be horizon-
of time an area must be defended justifies the
tal or nearly so.
effort and the ground lends itself to this pur-
(1) Entrances. The entrances must be
pose.
strengthened against collapse under shell fire
and ground shock from nuclear weapons. The
first 5 meters from each entrance should be
\-- ~.. ~
framed with timber supports using 10 cm x 10
.I\
\
cm or comparable timbers.
NENE.L.
(2) Size. Untimbered tunnels should be
about 1 meter wide and 1.5 to 2 meters high.
't>m
NOISYK\\Xw.
\N>\
'(3)
Chambers. Chambers may be con-
structed in rock or extremely hard soil without
6mf/
'"1
\
,
\
El
~
.
timber supports. If timber is not used the
CHAMNBE -'/
5 5mRANCE.
,
chamber (fig. 4-28) should not be more than
2 meters wide. If timbers are used the width
MG POSITION
may be increased to 3 meters. The chamber
·
N. Y- '-:
-T -7it'
should be the same height as the tunnel and
i-TUNNEL PASSES
up to 4 meters long.
(4) Grenade trap. These should be con-
\TRENCH
structed at the bottom of straight lengths
where they slope. It can be done by cutting a
recess about 1 meter deep in the wall facing
Figure 4-28. Tunneled defenses in Korea.
the inclining floor of the tunnel.
(5) Disposal of soil. A considerable quan-
b. Soil. The possibility of tunneling also de-
tity of spoil from the excavated area must be
pends to a great extent on the nature of the
disposed of and concealed. The volume of spoil
soil, which can be determined by borings or
similar means. Tunneling in hard rock is so
slow that it is generally impractical. Tunnels
in clay or other soft soils are also impractical
since they must be lined throughout or they
AGO 20013A
417
FM 5-15
is usually estimated as one-third greater than
danger that tunnel entrances will be blocked,
the volume of the tunnel. Approximately 100
trapping the occupants. Picks and shovels
tons of spoil were removed from the tunnel
must be kept in each tunnel so that men trap-
system shown in figure 4-28.
ped can dig their way out.
(6) Concealment. Tunnel entrances must
(2) Entrances. At least two entrances are
be concealed from enemy observation and it
necessary for ventilation purposes; whenever
may be necessary to transport spoil by hand
possible one or more emergency exits should
through a hand through a trench. Cold air
be provided. These last may be small tunnels
rising from a tunnel entrance may give away
whose entrances are normally closed and con-
the position.
cealed; a tunnel may be dug from inside the
e. Precautions.
system to within a few feet of the surface so
(1) Picks and shovels. There is always
that a breakthrough can be made if necessary.
4-18
AGO 20013A
FM 5-15
CHAPTER 5
OBSTACLE EMPLOYMENT
Section I. PRINCIPLES
5-1. Basic Considerations
of company size or larger should be blocked by
a. Definition. An obstacle is any terrain
a combination of obstacles and firepower.
feature, condition of soil, climate, or manmade
f. Nontactical Obstacles. Obstacles falling in
object other than firepower, that is used to
this category may be of the same general de-
stop, delay, or divert enemy movement.
sign as obstacles constructed under tactical
b. Purposes. Obstacles should be included in
conditions, but the same considerations of sit-
the overall defense plan to restrict the move-
ing and concealment do not apply. Nontacti-
ment of enemy forces, delay them, or require
cal obstacles may be used-
them to regroup,
(1) For the protection of important in-
c. Tactical Obstacles. The following obsta-
stallations against infiltration or sabotage.
cles are commonly referred to as tactical
(2) In civil policing operations to check
types:
the movements of rioters or to isolate a sec-
(1) Antitank obstacles intended to im-
tion of a town or city.
pede or stop the movement of track vehicles
(3) For administrative purposes.
across country or on roads;
(2) Antipersonnel obstacles constructed
5-2. Characteristics of Natural Obstacles
to slow up, confuse or divert enemy foot troops
Desirable characteristics of a natural obstacle
when they attempt to overrun or infiltrate a
are ease of conversion into a more effective
defended position or locality;
obstacle with a minimum of effort, materials,
(3) Antivehicle obstacles including road-
and time; defilade from enemy observation;
blocks, craters and other means that are used
location where observation and defensive fires
to stop or delay enemy wheeled vehicles so they
can prevent enemy breaching; and difficulty of
can be brought under aimed fire.
bypassing. The most effective natural obstacles
(4) Beach and river line obstacles that de-
against tanks are steep slopes,
unfrozen
lay, obstruct or divert enemy amphibious oper-
swamps, and broad, deep streams. Rice paddies,
ations.
lava fields, and similar areas can also be for-
d. Observation, Tactical obstacles must be
midable obstacles. Usually time, labor, and ma-
under observation and covered by fire for max-
terials can be saved by improving natural ob-
imum benefit. an obstacle which is not covered
stacles rather than constructing artificial ones
imum benefit. An obstacle which is not covered
by observed fire may be ineffective or at best
sae purpose.
a. Steep Slopes. Varying degrees of steep-
e. Offensive Use of Tactical Obstacles. Ob-
ness are required to stop different types of
stacles are used to anchor a flank or flanks of
vehicles. Tanks can negotiate slopes as steep
as 60 percent. However, trees, unfavorable soil
an advancing unit. They may also be used
an advancing unit. They may also be used
conditions, large rocks and boulders can make
behind enemy lines to delay, disorganize, and
slopes of less than 60 percent impassable, even
harass troop movements and communications,
though this would not be true if the same
especially when an enemy force is withdraw-
natural features were encountered on level
ing. The wide intervals between dispersed units
ground. The movement of infantry is also
AGO 20018A
5-1
FM 5-15
slowed down by steep slopes since movement
is slower and the troops tire more rapidly.
45-90cm
4 meters
45-90cm
b. Escarpments. A steep face of rock is a
formidable obstacle to both vehicles and per-
sonnel if it is over 11ll meters in height.
c. Ravines, Gullies, and Ditches. Ravines,
O
gullies, and ditches are generally obstacles to
(A) MARK THE SPACE
TO BE CUT
wheeled vehicles. If they are over 5 meters in
(B) REMOVE
THE SNOW
width, and approximately 2 meters in depth
and the banks are nearly vertical, they are
usually effective against tracked vehicles.)
O..
......
d. Rivers, Streams, and Canals. The major
obstacle value of rivers, streams, and canals
is that they must be crossed by special means,
(C)
SAW OUT THE ICE, CUTTING
ONE EDGE OBLIQUE
either deepwater fording, surface or aerial.
() FORCE
THE
ICE BLOCK
UNDER
The width, depth, velocity of the water, and
THE SURFACE
bank and bottom conditions determine the
WOODEN FRAME
COVERED
ease of crossing a water obstacle by deepwater
WITH TAR PAPER OR BRUSH
fording and floating equipment. However, a
river over 150 meters wide and over 11/. meters
deep is a major obstacle, limited only by the
presence of bridges, favorable sites for amphib-
ious vehicles, and fording sites. The obstacle
(E) CONSTRUCT
THE FRAME
value of fordable rivers, streams, and canals
is significant when the stability of the banks
and bottoms is considered. Although a few
SNOW COVER
vehicles may be able to ford a water obstacle,
the poor condition of the banks and bottom
CE4.5
meters min.
may prevent further use of the ford without
time-consuming improvement of the crossing
®.,
site. Stream velocity may likewise limit the use
.
of a ford and enhance its value as an obstacle.
/,
4 meters
e. Frozen Streams. Antitank obstacles (fig.
(F) REPLACE
THE SNOW
5-1) can be improvised in frozen streams by
cutting an opening about 3 to 4 meters wide
Figure 5-1. Antitank trap in ice.
in the ice and forcing the cut blocks of ice
under the solid surface so the blocks will be
are frozen solid enough to support vehicles and
carried downstream by the current. The open-
personnel.
ings are then closed with a light frame covered
g. Swamps and Marshes. The principal ob-
with cloth, brush, or tar paper with about a
stacle value of swamps and marshes is the
10 cm covering of snow. The effectiveness of
canalization of vehicular movement onto cause-
this type of obstacle depends on keeping the
ways thereby exposing the columns to air or
water in the channel from freezing. A well
artillery attacks. Swamps and marshes over 1
made trap will be effective for an extended
meter in depth may be better obstacles than
period of time if it is inspected frequently to
rivers, since causeways are usually more diffi-
maintain the snow cover. If the ice freezes
cult to construct than bridges. The physical
solid in the area of the trap, the procedure
effort required for foot troops to cross swamps
outlined above must be repeated.
and marshes is an important factor in thier
f. Lakes. Lakes are usually unfordable and
usefulness as an obstacle. All roads and cause-
unbridged and must be bypassed unless they
ways through swamps and marshes should be
5-2
AGO 20013A
FM 5-15
extensively cratered, mined, or blocked by aba-
be constructed to slow up or prevent the use
tis (fig. 7-8).
of floating equipment. The following obstacles
h. Forests. Forests have the effect of canal-
are effective against foot movement in the
izing movement, since the roads, trails, and
jungle:
fire breaks through them provide the only
(1) Punji jungle trap. Punji traps (fig.
means for rapid movement. The obstacle value
5-2) are most effective when they merge with
of a forest is dependent on tree size and den-
or resemble natural jungle obstacles. In the de-
sity, soil condition, slope, and depth. If the
fense, they may be used either as barricades
trees are at least 20 cm in diameter and suffi-
around camps or as barriers to impede the
ciently close together, they will seriously ob-
advance of an assault. In the offense, they may
struct or stop the movement of tanks. Even
be constructed behind enemy lines to stop or
though the trees are seldom close enough to-
hinder any retreat. Enemy patrols can be dis-
gether to stop tanks, they may prevent tank
banded by skillful use of these traps in con-
movement when they are pushed over and
nection with covering snipers. A pit 1.5 to 2
tangled. Much smaller trees (10 cm in diamet-
meters deep, about the same length and one
ter) will slow and sometimes stop tanks on 20
meter wide is dug in the middle of a jungle
percent slopes. Tree stumps that are 45 cm in
trail or at a stream crossing. A number of
diameter or larger are obstacles to tank move-
long, sharp punjis (bamboo spikes sharpened
ment. Forest undergrowth in the temperate
to a needle point) are placed upright in this
zone is not usually dense enough to seriously
pit, with the fire-hardened points slightly be-
obstruct foot movement, but such movement
low ground level (fig. 5-2). The pit is con-
will be slowed significantly by steep slopes,
cealed by a flimsy lid consisting of a bamboo
adverse soil conditions, and fallen trees and
lattice covered with a few bamboo creepers
branches. The most effective way of increasing
and camouflaged with mud or leaves to blend
the obstacle value of forests is to-
with the surrounding area. Anyone falling in-
(1) Construct abatis (fig. 7-8) or craters.
to the pit is instantly impaled on the spikes.
(2) Place mines along the roads, trails,
(2) Slit trench. A slit trench can be so
and firebreaks.
placed that enemy troops will be likely to use
(3) Construct log cribs, hurdles, and post
it. Like the cover of the punji pit, the bottom
obstacles if the necessary materials are avail-
able.
i. Jungle Obstacles. Tropical jungles are im-
portant obstacles to the movement of vehicles
and personnel. The ground between the trees
is usually covered by interwoven vines, bushes,
plants, or rotting vegetation. The ground is
often swampy or marshy. The tangled under-
growth and overhead foliage limits the visi-
bility and there are few if any paths or trails
i
except those that permit limited foot traffic.
Vehicles can seldom operate satisfactorily un-
less routes are prepared or extensively im-
proved. Foot troops are required to cut trails
through the dense undergrowth or move with
extreme difficulty. Since the jungle is an ef-
fective obstacle to movement, any roads or
trails that exist should be blocked and the
stream fords and amphibian vehicle entry and
exit sites should be mined. If the streams and
rivers provide the best routes, obstacles should
Figure 5-2. Punji jungle trap.
AGO 20013A
5-3
FM 5-15
of this trench is false, and underneath it are
type are most effective when they are sited on
sharp punjis, which will impale anyone jump-
an upgrade.
ing into the trench.
k. Deserts. The obstacle value of deserts is
that specially equipped vehicles and specially
po Snowf
Snow is considered deep for pur-
trained personnel are required to operate suc-
poses of foot or vehicle movement when the
cessfully in this environment Minefields are
meterage Snow at this
depth above
ground even deepervaton
is 1
comparatively easy to install and relocate in
meter. Snow at this depth and even deeper is
not unusual in the Arctic and the northern-
most regions of the temperate zone. It is found
C-
at these depths also in mountainous regions.
C
Deep snow and the accompanying ice and in-
tense cold combine to make obstacles of major
significance. Deep snow is an obstacle to move-
ment of both foot troops and vehicles. It also
4.0-4smtrs '
maters
4.8-i mtr
blankets terrain features such as boulders,
rocky areas, ditches, small streams and fallen
Figure 5-3. Antivehicular obstacle of packed snow.
trees so as to effectively impede movement.
The obstacle value of snow can be increased
cover up the usual signs of mine installation.
cover up the usual signs of mine installation.
~~~~~~~by-
1~~I.
Built-Up Areas. The natural obstacle of
(1) Erecting snow fences or breaks so
built-up areas can be increased by cratering
that the prevailing winds will accelerate the
streets, demolishing walls, overturning or de-
accumulation of snow into drifts to form snow
railing street or railroad cars, and construct-
obstacles of packed snow.
ing roadblocks from steel rails, beams, and rub-
(2) Building snow walls (fig. 5-3) as ob-
ble. When combined with mines and barbed
stacles against armor. The snow must be
wire, such obstacles are effective against ve-
packed hard for this purpose. Walls of this
hides and personnel.
Section II. ARTIFICIAL LAND OBSTACLES
5-3. Basic Considerations
into one of these three groups. More often
a. Definition. An artificial obstacle is any
than not an obstacle may be used for two or
manmade object constructed to hinder move-
three purposes. This arbitrary classification
ment. Artificial obstacles include minefields,
of-obstacles merely clarifies their primary uses.
antitank ditches, contaminated areas, hedge-
(1) Protective. Protective obstacles are
hogs, road craters, demolished bridges, and
those obstacles used to provide security. Ob-
barbed wire. They may be constructed en-
stacles of this type are usually artificial and
tirely on land or partially under water as in
include such items as wire, minefields, and
the case of beach and river line obstacles.
various warning devices. They are intended
b. Use. Major types of artificial obstacles
primarily to prevent the enemy from making a
are discussed separately in subsequent chap-
surprise assault from areas close to a position.
ters; however, they are normally used in con-
(2) Defensive. Defensive obstacles are ob-
junction with natural obstacles and in combin-
stacles used to delay the enemy force in areas
ations of two or more types of artificial ob-
where it can be engaged with heavy, intense,
stacles. When artificial obstacles are used in
defensive fire. They may be either natural or
barriers, a variety of them should be used,
artificial. A defended roadblock or an obstacle
when practicable, to increase effectiveness and
in front of a defensive position which stops or
as an aid to surprise and deception. Obstacles
delays the enemy force once it is in range of
can be divided into three groups according to
defensive weapons are examples of this type.
their uses. Seldom does an obstacle fall clearly
Defensive obstacles should be covered by ap-
AGO 20013A
FM 5-15
propriate fire, kept under observation, and
able of discouraging breaching, bypass, or
should be employed in conjunction with pro-
capture by personnel but should also be capable
tective obstacles.
of stopping any vehicles that may be used in
(3) Tactical. Tactical obstacles are ob-
the assault. Also, antivehicular obstacles must
stacles used to break up enemy attack forma-
be covered by fire that will not only destroy
tions and canalize the enemy force into areas
vehicles but will prevent troops from breach-
where it is blocked by defensive obstacles or
ing the obstacles and clearing a path for the
can be brought under intensive defensive fires.
vehicles.
Tactical obstacles delay, harass, or demoralize
(b)
Obstacles are best covered by dir-
the enemy by forcing him to employ dangerous
ect-fire weapons, but when this is not feasible,
or exhaustive breaching measures.
observed artillery fire and tactical air should
be used. Artillery covering obstacles should be
5-4. Principles of Employment
prepared to deliver fire that is effective against
a. Coordination with Tactical Plan. Obstac-
both personnel and vehicles. When it is impos-
les should be coordination with the tactical
sible to cover obstacles by fire, they should be
plan. All obstacles should contribute to the
contaminated or heavily boobytrapped to cause
success of this plan, and all units concerned
the enemy to employ dangerous and exhaustive
should know the location of and understand
breaching measures.
the purpose and type of obstacles employed.
c. Employment in Conjunction with Natural
In addition, all concerned should know when
and Other Artificial Obstacles. It is fundamen-
the obstacles are to be executed, and how long
tal that an obstacle system should usually be
they are to be defended. Only by coordina-
as difficult to bypass as it is to breach except
tion with all elements can an integrated plan
when the obstacle is intended to divert or de-
be prepared that will use all defensive meas-
flect the enemy rather than to delay or stop
ures to their best advantage against the enemy.
him. Artificial obstacles must be sited to take
b. Covering by Observation and Fire.
full advantage of natural and other artificial
(1) Observation. If accurate fire is to be
obstacles, so as to keep logistic and construc-
delivered on an obstacle or obstacle system, it
tion requirements to a minimum. Natural ob-
must be under observation. The observation
stacles are improved and exploited to the full-
and defense of obstacles for close-in defense
est extent as described in paragraph 5-2.
is the responsibility of the unit occupying the
d. Employment in Depth. Obstacles do not
ground. However, when an obstacle system
seriously hamper the enemy's movement until
covers a large area, observation is normally
they overload or heavily tax his breaching cap-
the responsibility of roving patrols, an out-
abilities. ThTs cannot be accomplished unless
post system, Army aviation, or tactical air.
obstacles are employed in depth. With the ex-
Their final defense is a mission for mobile
ception of contaminated areas it is usually pro-
forces that can be brought quickly to any
hibitive in time and materials to construct a
point of the system. At times it is not feasible
large deep area of continuous obstacles. The
to have an obstacle under direct observation.
same end is accomplished by constructing suc-
When this is the case, warning devices or
cessive lines of obstacles, one behind the other,
alarm systems such as tripflares, boobytraps,
as time and conditions permit. These succes-
in connection with noisemakers should be used.
sive lines require the enemy force to continual-
(2) Fire. Covering an obstacle by fire us-
ly deploy and regroup, thus dissipating, can-
ually means the difference between causing the
alizing, and dividing its effort until friendly
enemy only small delay and annoyance and
forces can destroy it or force its withdrawal.
forcing him into a costly engagement.
e. Camouflage and Concealment.
(a) Both antivehicular and antiperson-
(1) Camouflage. Obstacles should be cam-
nel obstacles should be covered by both antive-
ouflaged or employed in such a way that they
hicular and antipersonnel fire. Fire that covers
come as a surprise to the enemy. When the
antipersonnel obstacles should not only be cap-
enemy has no prior knowledge of an obstacle,
AGO 20018A
5-5
FM 5-15
he has to reduce it without benefit of prior
Lanes and gaps should be covered by fire to
planning. If the obstacle is defended the de-
preclude the possibility of the enemy rushing
fender has the advantage of the enemy's first
through them before they can be closed.
reaction, which is usually confusion, and the
g. Affording No Advantage to the Enemy.
enemy may be caught without the men and
Enemy forces may use certain obstacles to an
material to breach the obstacle.
advantage as they are breached or assaulted.
(2) Siting. Proper siting is often the
Antitank ditches should be so constructed as
easiest solution to obstacle camouflage pro-
to be useless to the enemy as fighting trenches.
blems. Large obstacle systems cannot be con-
Log cribs should be so located that the enemy
cealed by siting alone, but when proper ad-
cannot deliver effective fire on defending
vantage is taken of the terrain and the ob-
weapons while using the crib as a breastwork.
stacles are located in folds of the ground,
Care should be taken that obstacles are not
around blind curves in roads, or just over the
located so that the enemy can use handgrenades
tops of hills, they can be made inconspicuous
against the defenders from cover or conceal-
from the enemy's ground observation. To help
ment provided by the obstacles. Barbed wire,
camouflage obstacles from aerial observation,
mines, and boobytraps should be used exten-
regular geometric layouts of obstacles and bar-
sively to deny use of any cover or concealment
rier systems should be avoided and phony ob-
that might be provided to the enemy by na-
stacles used to confuse the enemy as to the
tural or artificial obstacles. Care should be
exact location and extent of the system.
taken to guard against the inadvertent plac-
(3) Concealment. The best way to conceal
ing of an obstacle which might later hinder
an obstacle usually is to postpone its execution
friendly maneuver.
or construction as long as possible, without in-
terfering with its readiness when needed. This
5-5. Minefields
cannot be done when large barrier systems
Minefields are not only an obstacle to the ad-
are involved but is possible when preparing
Vance of the enemy but unlike obstacles of a
obstacles to block narrow avenues of approach,
passive nature, they can also inflict significant
such as roads or bridges. Obstacles created
casualties; therefore minefields are considered
by demolitions lend themselves readily to this
the best form of artificial obstacle. The instal-
procedure. When their use is contemplated
lation of minefields changes favorable terrain
they should be completely prepared for firing
to unfavorable terrain and materially enhances
at the last minute.
the strength of the defense system. Mines and
f. Provision for Lanes and Gaps. Whenever
minefields are covered in FM 5-31, FM 20-32,
obstacles are employed around a defensive posi-
and TM 9-1345-200.
tion or area, lanes or gaps through the sys-
5-.
Caltrops
tem are left and concealed. These lanes are
a. Description. A caltrop (fig. 5-4) has four
provided so that patrols, counterattacks, and
sharpened prongs oriented so that one prong
friendly troops on other missions may move
will always be vertical regardless of how the
through the system without difficulty. Under
caltrop lands. The prongs are 3/32 inches in
normal circumstances the lanes or gaps nec-
diameter and 11/ inches long.
essary to mount a general offensive through
b. Uses. Caltrops are employed as antiper-
the obstacle system are not provided during
sonnel obstacles either by themselves or in
construction, but prepared later when the need
conjunction with barbed wire. When emplaced
for them arises. It is important that there be
with a density of 38 per meter of barrier front,
a sufficient number of lanes to allow for alter-
an effectiveness equivalent to triple standard
nate use and that they be concealed and
concertina is achieved. Caltrops are designed
changed periodically to insure that they are
to cause injury by penetrating the footgear of
not discovered by the enemy. Prior plans must
a man who steps on one. Serious injury will
exist to insure that all lanes or gaps can be
result if a man quickly falls to the ground to
blocked quickly when enemy action is expected.
avoid small arms or artillery fire. Caltrops can
5-6
AGO 20013A
FM 5-15
be dispensed by hand, from the rear of a
truck, or from fixed and rotary winged air-
craft.
5-7. Barbed Wire Entanglements
Obstacles constructed from barbed wire are
simple, flexible and effective against personnel.
They may also be used to impede the movement
of vehicles. Barbed wire entanglements are
discussed in detail in chapter 6.
5-8. Antivehicular Obstacles
In defensive positions, antivehicular obstacles
are used to obstruct gaps between natural ob-
stacles or they can be placed in a continuous
line of considerable length in open terrain.
Antivehicular obstacles are usually employed
in conjunction with wire entanglements, mine-
fields, and other obstacles. Under some condi-
tions they may be continuous in areas just in-
land of beaches. Antivehicular obstacles are
discussed in detail in chapter 7.
Figure 5-4. Caltrop.
Section III. BEACH AND RIVER LINE OBSTACLES
5-9. Responsibility
requires adequate anchorages for assault ship-
In unilateral Army shore-to-shore amphibious
ping and shore for beaching large landing
operations, Army forces are responsible for the
craft. Where the overwater distance is short,
installation and removal of beach and under-
however, or where the enemy can develop a
water obstacles. In joint Army-Navy amphibi-
nearby base in neutral or unoccupied territory,
ous operations, Navy forces are normally
shore-to-shore operations are practicable, using
responsible for removal of obstacles on a hos-
smaller craft capable of landing troops and
tile shore seaward from the high waterline. The
vehicles at almost any point. Against either
underwater demolition teams (UDT) of the
of these types of operation, antiboat and anti-
Navy have the responsibility of removing ob-
personnel obstacles at wading depths are de-
stacles from the high waterline to the 3-fathom
sirable in most situations. Antipersonnel ob-
(5.54 meters) line. Beyond that point Navy
stacles so located, however, are not effective
minesweepers clear boat and shipping lanes.
against large landing craft if the latter can
The responsibility for installation of beach
beach at the waterline or can side-carry floating
and underwater obstacles in friendly territory
causeways and use them to get ashore.
is assigned by the commander of the forces
a. Beach Obstacles. Beach obstacles are de-
involved.
signed to force landing craft to unload at low
tide several hundred yards seaward of the
5-10. Ocean Beach Defenses
high watermark. Thus, on beaches with grad-
An assault across an ocean normally involves
ual slopes assaulting infantry must cross a
a ship-to-shore assault in which the enemy
wide expanse of obstacle-studded beach cov-
AGO 20013A
5-7
FM 5-15
ered by heavy defensive fire before reaching
mum obstacle effect at the tide stage at which
the high watermark. At high tide, beach and
an assault is probable and for maximum effec-
underwater obstacles should be covered by just
tiveness
against
amphibious tracked and
enough water so that they cannot be seen by
wheeled vehicles.
personnel in landing craft. When landing craft
b. Beach Slopes. Due to tide and current
strike the obstacles they are disabled and the
action, beaches and river lines tend to fall into
assaulting troops are forced to disembark in
two general types-those with steep slopes
deep water.
into deep water, and those with gradually slop-
b. Antiboat Obstacles. Antiboat obstacles are
ing bottoms for a considerable distance off-
constructed at varying heights so they are
shore. Each type has advantages and disad-
about 30 to 60 cm below the surface of the
vantages for the defense. The steep slope
water at high tide, echeloned in depth in vari-
prevents debarkation until boats reach the
ous arrangements of which those shown in
beach, but it renders placing underwater ob-
figure 5-5 are typical.
stacles more difficult. The gentle slope facili-
tates placing obstacles but it also allows the
attacking troops to disembark while
still
afloat.
(1) Steep. For beaches with steeply slop-
BEAC:
X
* Ad~lling
bottoms, provision should be made for
LO. TIOE
stopping landing craft offshore in deep water.
\-0 'KThe obstacles may include mines of various
types anchored just below the waterline, float-
Figure 5-5. Antiboat obstacles in beach defense.
ing log booms anchored or tied to shore, which
may have mines attached, and heavy chains of
5-11. River line Defenses
wire rope stretched between pile dolphins.
All possible means of crossing are studied, in-
Preferably such obstacles should be submerged
cluding assault boats, footbridges, fixed and
so as to be out of sight but tide variations may
floating vehicular bridges, and the use or re-
make this impracticable. In such cases a com-
habilitation of existing bridges. In addition to
promise must be made between minimum visi-
antiboat and antipersonnel obstacles, the de-
bility and maximum practicable effectiveness.
fender considers the use of obstacles to hamper
Where possible, provision is made for adjusting
the enemy's bridging activities and his instal-
the height of log booms and the like, to con-
lation of booms and other protective devices
form with water level fluctuations.
to protect bridges.
(2) Gradual. For beaches with gradually
sloping bottoms, the defense attempts to pre-
5-12. Effective Obstacles
vent landing craft from reaching the beach or
a. Siting. The basic requirements for arti-
from reaching wading or fording depth for
ficial obstacles and their employment apply
personnel and vehicles. In addition to obstacles
equally to beach and river line obstacles. Of
of the types described above, in water of wad-
particular importance are the requirements
ing depth the bottom is covered thoroughly
that artificial obstacles be used to exploit nat-
with underwater wire entanglements of all
ural obstacles, that they be inconspicuous, be
types. These must be anchored in place very
kept under surveillance, and be capable of be-
securely to prevent damage from surf or cur-
ing covered by fire. Gaps and lanes are pro-
rents and so that both enemy and friendly fire
vided and are marked or referenced for the
will tend to form tangles rather than to clear
use of friendly troops. Antiboat obstacles
lanes. In such entanglements, channels pro-
selected for use should be of a type which will
vided for passage of friendly small boats may
be effective against boats which can operate
be closed rapidly by the use of anchored con-
in the surf, current, and various wind condi-
certinas or weighted spirals.
tions to be expected. They are sited for maxi-
c. Employment in Depth. Beach obstacles
5-4
AGO 2001A
FM 5-15
are typically established in bands in depth,
stacles. These are installed beginning at low
as follows:
waterline and extending inshore across the
(1) Antiboat obstacles. These are located
width of the beach. Mines or other obstacles
from wading depth at low tide to wading
are normally installed at the beach exit.
depth at high tide.
(4) Antivehicular ditches. These are dug
(2) Barbed wire entanglements. These are
beginning at the inshore edge of the beach,
placed from wading depth at high tide, inshore
where concealment is possible.
across the width of the beach.
(5) Other obstacles. These are located in-
(3) Antivehicular and antipersonnel ob-
shore of the beach area, in the same manner
as obstacles for land defense.
AGO 20018A
59
FM 5-15
CHAPTER 6
BARBED WIRE ENTANGLEMENTS
Section I. MATERIALS
6-1. Concept
and to hold the enemy in areas covered by the
a. Purpose. Barbed wire entanglements are
most intense defensive fire. Tactical entangle-
artifical
obstacles designed to impede the
ments extend across the entire front of a posi-
movement of foot troops and, in some cases,
tion but are not necessarily continuous.
tracked and wheeled vehicles. The materials
(b) Protective. Protective wire entan-
used in constructing barbed wire entangle-
glements are located to prevent surprise as-
ments are relatively lightweight and inexpen-
saults from points close to the defense area.
sive, considering the protection they afford.
As in the case of all antipersonnel obstacles,
Barbed wire entanglements can be breached
they are close enough to the defense area for
by fire but are rapidly built, repaired, and
day and night observation and far enough
reinforced.
away to prevent the enemy from using hand-
b. Siting and Layout. To be effective, barbed
grenades effectively from points just beyond
wire entanglements are sited and laid out to
the obstacle, normally 40 to 100 meters. Pro-
meet the following requirements:
tective wire surrounds the individual units of
(1) Under friendly observation, covered
a command, usually the platoons (fig. 6-1).
by fire, and where practicable, protected by
These entanglements should be connected to
antipersonnel mines, flame mines, tripflares,
entanglements around other platoons by sup-
and warning devices.
plementary wire to enclose the entire defen-
(2) Concealed from enemy observation as
sive positions. Protective entanglements
are
far as practicable
by incorporating terrain
erected around rear-area installations in the
features such as reverse slopes, hedges, woods,
same manner and to serve the same purpose
paths and fence lines.
as protective wire around defensive positions
(3) Erected in irregular and nongeomet-
in forward areas. Protective wire also includes
rical traces.
the entanglements which should be installed
(4) Employed in bands or zones wherever
over the tops of installations provided with
practicable.
overhead cover (fig. 6-2).
(5) Coordinated with other elements of
(c)
Supplementary.
Supplementary
the defense.
wire entanglements in front of the forward
c, Classification. Entanglements are classi-
edge of the battle area are used to conceal the
fled according to their use and their depth and
exact line of the tactical wire. To the rear of
whether fixed or portable.
the FEBA, supplementary wire is used to in-
(1) Use. Entanglements are classified by
close the entire defensive position by connect-
use as tactical, protective, or supplementary.
ing the protective wire entanglements. Supple-
The employment of these types in a defensive
mentary wire entanglements used to break up
area is shown schematically in figure 6-1.
the line of tactical wire should be identical to
(a) Tactical. Tactical
wire entangle-
the tactical'
wire entanglements and con-
ments are sited parallel to and along the
structed simultaneously with them whenever
friendly side of the final protective line. They
possible.
are used to break up enemy attack formations
AGO 20018A
6-1
FM 5-15
(2) Depth. Entanglements are classified
(1) Outpost area. The combat outposts
by depth as belts, bands, or zones.
should be surrounded with wire entanglements.
(a) Belt. A belt is an entanglement one
These entanglements should be carefully sited
fence in depth.
to serve as both protective and tactical wire
(b) Band. A band consists of two or
and must be covered by small arms fire. The
more belts in depth, with no interval between
wire obstacle should be supplemented by anti-
them. The belts may be fences of the same
personnel mines, warning devices, and booby-
type, or the band may be composed of two or
traps.
more fences of different types.
(2) Battle position. In the battle area,
(c) Zone. A zone consists of two or more
each company defense position is normally sur-
bands or belts in depth, with intervals between
rounded by a wire entanglement which is con-
them.
nected laterally across the front to the entan-
(3)
Equivalent effectiveness. Entangle-
glements surrounding the other units in the
ment depths are also described or specified in
position.
terms of comparative effectiveness. Tactical
(3) Artillery and reserve area. Wire en-
wire entanglements should be equivalent in ef-
tanglements are used in the outer protection
fectiveness to three
belts of 4- and 2-pace
of howitzer positions. Heavier weapons, and
double apron fence whenever possible. Protec-
shelters or other installations in the reserve
tive wire may employ any type of entangle-
area, are similarly protected if justified by the
ment provided its effectiveness is at least the
situation.
equivalent of that of the 4- and 2-pace double
(4) Antipersonnel obstacles. Barbed wire
apron fence. Supplementary wire should have
entanglements, tripflares, noisemakers, and an-
an effectiveness equivalent to that of the type
tipersonnel mines are sited to warn against
of wire it supplements. It should be equivalent
enemy patrol action or infiltration at night;
to tactical wire or equivalent to the type of
to prevent the enemy from delivering a surprise
protective wire being used if it connects the
attack from positions close to the defenders;
outer perimeters of protective wire at the
and to hold, fix or delay the enemy in the most
flanks and rear.
effective killing ground. Such obstacles should
(4) Portability.
be near enough to defensive positions for ade-
(a) Fixed entanglements
are those
quate surveillance by the defenders by night
types which must be erected in place and
and day and far enough away to prevent the
which cannot be moved unless completely dis-
enemy from using handgrenades against the
assembled.
defender from points just beyond the obstacles.
(b) Portable entanglements are those
f. As Roadblocks. A series of barbed wire
types which can be moved without complete dis-
concertinas as shown in figure 6-3 will stop
assembly. Portable entanglements have been
wheeled vehicles. A series of these blocks
developed for one of the following reasons: To
placed about 10 meters apart should be used.
permit assembly in rear areas, with ease of
The ends of adjacent coils are wired together
transportation and rapid installation in for-
and the obstacle lightly anchored at the sides
ward positions. For the temporary closing of
of the road. The block should be sited to
gaps.or lanes which can be reopened quickly
achieve surprise.
for patrols or counterattacking forces.
g. To Strengthen Natural Obstacles. Deep
rivers, canals, swamps, and cliffs which form
d. Lanes and Gaps. Lanes and gaps are pro-
effective delaying obstacles to infantry, and
vided for the passage of patrols, working par-
thick hedgerows, fences, and woods
which
ties, and attacking or counterattacking forces
are only partial obstacles, can be improved by
When not in use they are kept closed by the use
lacing with barbed wire, by the addition of
of portable obstacles covered by fire. In barbed
parts of standard fences on one or both sides,
wire zones, lanes and gaps are staggered on a
or by entangling with loose wire.
zigzag pattern.
e. Uses.
6-2
AGO 20013A
FM 5-15
LEGEND
6
TACTICAL WIRE
-x-x-
PROTECTIVE
WIRE
=->o<-
SUPPLEMENTARY
WIRE
Figure 6-1. Schematic layout of barbed wire entanglements in a defensive area.
6-2. Standard Barbed Wire
a. Description. Standard barbed wire is 2-
strand twisted No. 12 steel wire with 4-point
bars at 10 cm spacing (fig. 6-4).
b. Handling. In handling barbed wire, the
standard barbed wire gauntlets (FSN 8415-
.:
0t; AdE Ft
~
,
268-7873) shown in figure 6-4 or heavy leather
gloves are worn. They permit faster work and
avoid cuts and scratches. As an added safety
· ,
~precaution, the wire should be grasped with
the palm down.
c. Issue. Barbed wire is issued in reels (fig.
, 6-5) containing about 400 meters of wire. The
wire weighs 40.8 kgs and the reel 0.6 kgs. In
building a fence, two men carry one reel.
d. Bobbins. Bobbins (fig. 6-6) holding about.
II I'
30 meters of wire are prepared, normally in
, ! . _l // I1'
]
rear areas, for use in building short lengths
of fence and in repairing entanglements. In
use, two men handle one bobbin. One unwinds
the bobbin while the other installs the wire.
~,$ " i~~~en~
~
~
Two or more men may make the bobbins as
., c~ :; . ;
~.follows:
(1) The bobbin sticks are prepared.
(2) The reel is rigged on an improvised
trestle or other support.
(3) One man unrolls and cuts 30-meter
Figure 6-2. Protective wire on top of overhead cover.
AGO 2oo01A
6-3
FM 5-15
lengths of wire, fastening one end of each to
the trestle.
(4) The wire is wound in figure-of-eight
shape on the bobbin sticks.
/~2.5
ROUND OR SARE
Figure 6-F. Concertina roadblock.
e.
(5) A piece of white tracing tape should
-
isi
o
20
2.5cm
ROUND
OR SQUARE
5
2
finding it.
3R
IO
RED
ID METHOD OF MAKING BOBBIN
FREE END MARKED
WITH WHI
TAPE
@ COMPLETED BOBBIN
Figu
T
Figure
6-6-6.
Barbed wire bobbin.
should be used instead of the standard gaunt-
(5)
A piecgure
of-.
Standard barbed wire.
lets. Small metal clips on the palm and fingers
63.
Barbed Steel Tape
prevent the barbs of the tape from cutting the
a. Description. Barbed steel tape is 1.91 cm
leather (fig. 6-8).
wide steel tape that is .55-mm thick with a
c. issue. The barbed tape is issued in 50-
barbed interval of 1.27 cm (fig. 6-7).
meter reels weighing 2.4 kg. There are six
b. Harbe
dlinvg. In handling barbed tape, heavy
reels to a cardboard carrying case.
barbed tape gauntlets (FSN 8415-926-1674)
d. Barbed Tape Dispenser. A dispenser (fig.
6-4
AGO 20013A
FM 5-15
f
_
,,I<
;
.-
3.
c
r
%-
t
SCALE
I" GRID
Figure 6-7. Barbed steel tape.
6-9) is required to install barbed tape. It con-
barbed tape is more difficult to breach by crawl-
sists of a frame to hold the 50-meter reel of
ing through than one constructed with stand-
barbed tape and two sets of rollers. The reel
ard barbed wire because the barbs of the
is inserted on the spindle and the tape is
barbed tape are closer together. Because of the
threaded through the two sets of parallel roll-
flat configuration, it is more difficult to cut
ers. The outside set of rollers are then turned
barbed tape with wire cutters.
90 ° in a clockwise direction. The hinged arm
(2) At the present time, the major dis-
of the frame is then closed and locked in place
advantage of barbed tape is the breaking
by the frame of the rotating rollers. As the
strength. Standard barbed wire is twice as
tape unwinds from the reel, the two sets of
strong. Installation of barbed tape requires a
rollers oriented 900 to each other impart a
dispenser. A major problem could arise if the
twist to the tape. To be effective the barbed
dispenser is not available. The tape is not re-
tape must be twisted as it is installed.
coverable to its original condition. However, it
e. Uses. Barbed tape can be used in place of
may be recovered on bobbins in the twisted con-
standard barbed wire in most all cases except
dition. Barbed tape is more easily cut by shell
when it is to be repeatably recovered and re-
fragments than standard barbed wire. Barbed
used. The most effective fence that can be
tape can also be cut with a bayonet.
constructed using barbed tape is the double-
apron fence.
Wire entanglements are supported on metal or
(1) The principal advantages of barbed
wood pickets.
tape are its size and weight. For equal lengths,
a. Metal Pickets. Metal pickets are issued in
barbed tape occupies a third of the space and
two types, screw and U-shaped. The standard
weighs a third as much as standard barbed
lengths are short or anchor, medium, and long
wire. A double-apron fence constructed with
AGO 20013A
6-5
FM 5-15
Screw pickets tend to be less rigid than other
types but are desirable because they can be
,>^f:-,.s
zip
_, !,
installed rapidly and silently. When silence is
necessary, the driftpin used in installing the
pickets should be wrapped with cloth.
(2) U-shaped picket. The U-shaped picket
is a cold-formed steel picket of U-shaped cross
section, pointed at one end for driving. It is
notched for wire ties and the pointed end has
a punched hole for wires used in bundling the
pickets. U-shaped pickets are driven with a
Figure 6-8. Barbed tape-wire gauntlets.
SCREW PICKET
U-SHAPED PICKET
WOODEN PICKET 8pT
(fig. 6-10). The U-shaped picket also comes
4'
7FT.
in an extra long length. Pickets that are serv-
_.
iceable are recovered and used again.
6FT
5 FT.
4_FT
a.
SHORT LONG
SHORT LONG
SHORT EXTRA
NO
_EDIUM
_EDIU L*TRA
LONG LONG
l-
Figure 6-o10. Pickets for use with barbed wire.
sledge hammer. A stake driving cap (FSN
5340-220-8457) is used on tip of the picket
to prevent a sledge from deforming it. Driv-
ing the pickets is noisier than installing screw
pickets. However, noise may be cut down some-
what by placing a piece of rubber tire over the
driving face of the sledge. The pickets are
rigid and sturdy when properly installed and
are preferable to screw pickets in situations
Figure 6-9. Barbed tape dispenser with 50-meter
where noise is not a disadvantage and time is
reel of tape.
available. The pickets are driven with the hol-
low surface or concave side facing enemy fire
because small arms projectiles ricochet from
screwed into the ground by turning it in a
the convex side. An exedient picket driver
clockwise direction using a driftpin, stick, or
which can be locally fabricated is shown in
the picket for leverage. The bottom eye is used
figure
11 Constructed as shown it weighs
approximately 12 kilograms and is operated by
in order to avoid twisting the picket. Screw
pickets are installed so that the eye is to the
two men. One man holds the picket in a vertical
right of the picket, as seen from the friendly
position
hile the other slides the driver over
side, so standard
ties can be easily made.
the picket and starts it into the ground. Then,
side, so standard ties can be easily made.
AGO 200111A
FM 5-15
both men work the picket driver up and down
used as pickets when their location permits.
until the required depth is reached. Short pick-
c. Reference. Table 6-1 lists information per-
ets can be driven by turning the picket driver
taining to materials used in the construction
upside down and using the head as a hammer.
of barbed wire entanglements.
The bucket of a frontloader can be used to push
6-5. Con
ina Fencing
U-shaped pickets into the ground if the tacti-
a. Standard Barbed Wire Concertina. The
cal situation permits the use of equipment.
standard barbed wire concertina (fig. 612)
(3) Arctic adapter. For erecting barbed
is a commercially manufactured barbed wire
wire obstacles with U-shaped drive pickets
obstacle made of a roll of single-strand, high-
under conditions where frozen ground prevents
strength, spring-steel wire with 4-point barbs
driving the pickets, an Arctic adapter is avail-
attached at 5 cm spacing. Wires forming the
able for anchoring the pickets. The adapter is
coils are clipped together at intervals so that
made of steel and consists of a base plate
the concertina opens to a cylindrical shape 15
equipped with an adjustable channel recepta-
meters long and 90 centimeters in diameter.
cle and two anchor pins. It is anchored by
The concertina is easily opened and collapsed
driving the anchor pins through holes in the
and can be used repeatedly because the wire
base plate into the ground. One anchor pin
returns to its original shape after a crushing
drive sleeve with driving pin is provided with
force is applied and then removed. The wire
each 20 adapters to facilitate anchor pin em-
is much harder to cut than standard barbed
placement. When adapters are not available,
wire. The concertina weighs 25.4 kgs.
a hole can be started with a pick and the picket
can be frozen in place by pouring water and
HEAD.¥ 2 MILD STEEL PLATE
snow into the hole.
WELDED TO ENDS OF PIPE
b. Wooden Picket. Expedient wooden pickets
of several types may be used.
(1) Round poles 10 cm in diameter are
cut to standard picket lengths, sharpened on
one end, and driven with a maul. The pickets
are used without peeling the bark to prevent
2STEEPIPE
t~
~
~
MILDSTEEL PIPE
the wire from sliding on the picket and to sim-
FOR HANDLES
plify camouflage. Longer pickets are required
_
ND
in loose or sandy soil or when driving through
a snow cover. The driving of wooden pickets
-3
MILD STEEL
is not as noisy as the driving of steel pickets,
GUIDE PIPE
and the noise can be reduced further by fasten-
ing a section of tire tread over the face of the
RAD ~l
WELD
hammer or maul. For driving in hard earth,
picket tops are wrapped with wire to avoid
(a) SECTION
splitting. Pickets of hardwood, properly in-
stalled, are sturdy and rigid.
8
_,
(2) Dimension lumber ripped to a square
cross section may be used instead of round
.
VRAD
poles. This is equally satisfactory except that
it is more difficult to camouflage. Such pickets
may be dipped in camouflage paint prior to
(b) PLAN OF HEAD
driving.
(3) Standing trees and stumps may be
Figure 6-11. Expedient picket driver.
AGO 20018A
6-7
FM 5-15
Table 6-1. Wire and Tape Entanglement Materials
Approx
Approx
No. car-
Approx weight
Material
weight,
Iength,
ried by
of mn-load
kg
m
one man
kg
Barbed wire reel ---.-------
41.5
400
2
21
Bobbin
.-----.......------
3.5-4.0
30
4-6
14.5-24.5
Barbed tape dispenser --
.--
0.77
0.45
20
15.5
Barbed tape carrying case
14.5
300
1
14.5
Standard barbed tape concertina --
-
14
15.2
1
14
Standard barbed wire concertina
25.4
15.2
1
25
Expedient barbed wire concertina
13.5
6.1
1
13.5
Screw pickets:
Long
- -------
-------------
-
4
1.6
4
16.3
Medium
2.7
0.81
6
16.3
Short
-
-----------------
-
-
-
1.8
0.53
8
14.5
U-shaped pickets:
Extra long
7.25
2.4
3-4
21.8-29.0
Long -4.5
1.5
4
18.1
Medium
2.7
0.81
6
16.3
Short -- --------------------------
1.8
0.61
8
14.5
Wooden pickets:
Extra long ------
1 7.7-10.5
2.13
2
15.4-20.8
Long -------
----------------------
5.4-7.25
1.5
3
16.3-21.7
Short
-------------------------
1.4-2.7
0.75
8
11.0-21.7
around the carrying handle for use in retying
the concertina when it is again collapsed. Four
men open a concertina and extend it to the
15-meter length, with one man working at
each end and others spaced along its length
to insure that it opens and extends evenly.
AND CET
P RB
When necessary, two men can easily open a
concertina by bouncing it on the ground to
prevent snagging as they open it.
~~~EXTENDED LENGTH
~(b)
To collapse concertina. Two men
15m
can collapse a concertina in the following man-
ner: First all kinks in coils are removed. Loose
clips are then tightened or replaced with plain
CLOSED THICKNESS
wire. To close the concertina, one man stands
15cm
'2[
at each end of it and places a foot at the
DIAMETER CLOSEDI
D~IAMEtER~~~
CLbottom
of the coil and an arm under the top
DIAMETER OPEN
of the coil. The two men walk toward each
90cm
other closing the concertina by feeding the
wire over their arms and against their feet.
When closed, the concertina is laid flat and
Figure 6-12. Standard barbed wire concertina.
compressed with the feet. The concertina is tied
with plain wire bindings.
(1) Handling.
(c) To carry concertina. One man easily
(a) To open concertina. The collapsed
carries the collapsed concertina by stepping
concertina is tied with plain wire bindings
into it and picking it up by the wire handles
attached to the quarter points of a coil at one
attached to the midpoints of an end coil.
end of the concertina. In opening the concer-
(2) Staples. Improvised staples approxi-
tina, these bindings are removed and twisted
6-8
AGO 20013A
FM 5-15
mately 45 cm long and made of 1/2-inch drift-
and an expanded length of 15.2 meters. It is
pins or similar material are used to fasten the
formed of barbed tape wrapped around a high
bottoms of concertina fences securely to the
strength, spring steel, core wire. Its configura-
ground.
tion, method of handling, and method of em-
b. Barbed Steel Tape Concertina. Barbed
ployment are similar to standard barbed wire
tape concertina comes in a diameter of 85 cm
concertina. One role weighs only 14 kg.
Section II. CONSTRUCTION PROCEDURES
6-6. Organization of Work
lets. The sequence of operations for each fence
Table 6-2 gives the materials and man-hours
is given in the paragraph describing the erec-
required for entanglements of the various
tion of the fence. The sequence that is outlined
types. The normal sizes of work crews are given
should be followed, and as experience is gained,
in the descriptions of the entanglements. For
the size and composition of the groups may be
each construction project, the senior noncom-
varied. For each section of entanglement, all
missioned officer divides his crew into groups
fence-building operations normally proceed
of approximately equal size, based on his
from right to left, as one faces the enemy. It
knowledge of the skill and speed of each man.
may, however, be necessary to work from left
He organizes them in such a way that construe-
to right, and men should, if time permits, be
tion proceeds in proper order and at a uniform
taught to work in either direction. In case of
rate. Each individual must know exactly
heavy casualties, senior officer or NCO will
what his group is to do and his job in the group.
decide what wires, if any, are to be omitted.
Each man should have barbed wire gaunt-
Table 6-2. Material and Labor Requirements for 300-Meter Sections of Various
Barbed Wire Entanglements
Barbed
Kgs of
Man-hour
Pickets
wire No.
No. of
materials
to erect
Type of entanglement
of 400 m,
concer- Staples
per lin
800 m of
Extra
41.5 kg
tin.'
of
entangle-
long
Long
Medium
Short
reels
entnglement
ment
Double-apron, 4- and 2-pace
100
-
200
14-15(19)'
4.6(3.5)'
59
Double-apron, 6- and 3-pace
_
_
_
66
132
13-14(18)-
3.6(2.6)'
49
High wire (less guy wires)
198
.-- -
17-19(24)
5.3(4.0)'
79
Low wire, 4- and 2-pace
...
.
-
-
100
200
11(15)'
3.6(2.8)'
49
4-strand fence
.-..
100
2
5-6(7)'
2.2(1.8)'
20
Double expedient concertina .
101
--
4
3
100
295
6.9
40
Triple expedient concertina ---
51
101
--
7
4
148
295
10.4
99
Triple standard concertina ----
160
---
4
3(4)-
59
317
7.9(5.4)-
30
1 Lower number of reels applies when screw pickets are used: high number when U-shaped pickets are used. Add difference between the
two to the higher number when wood pickets are used.
'Average weight when any issue metal pickets are used.
a Man-hours are based on the use of screw pickels. With the exception of the triple-standard concertinas, add 20 percent to the man-hours
when driven pickets are used. With experienced troops. reduce man-hours by one-third. Increase man-hours by 50 percent for nightwork.
Based on concertinas being made up in rear areas and ready for issue. One expedient concertina opens to 6-meter length, as compared
with 15 meters for a standard concertina: it requires 92 meters of standard barbed wire. alo small quantities of No. 16 smooth wire
for ties.
Number of 300 m. 14.5 kg barbed tape carrying cases required if barbed tape is used in place of barbed wire.
KCgs of materials required per linear meter of entanglement if barbed tape is used in place of barbed wire and barbed tape concertina
is used in place of Standard barbed wire concertina.
a. Construction at Night. For night con-
(1) Tracing tape should be laid from the
struction the following additional preparations
materials dump to the site of work and then
are made:
along the line of fence where possible.
AGO 20013A
69
FM 5-15
(2) Materials should be tied together in
man loads and pickets bundled tightly to pre-
vent rattling.
(3) Wire fastenings of wire coils and
pickets should be removed and replaced with
string which can easily be broken.
(4) A piece of tape should be tied to the
ends of the wire on each reel or bobbin.
b. Supervision. Proper supervision of en-
TOP EYE TIE
INTERMEDIATE-EYE TIE
tanglement construction includes the follow-
ing:
(1) Proper organization of the work into
tasks.
(2) Making sure the tasks are carried out
-in the proper sequence.
(3) Prevention of bunching and over-
crowding of personnel.
(4) Making sure the wires are tightened
properly and spaced correctly.
(5) Checking ties to see that they are
APRON TIE
POST
IE
being made correctly and at the right points.
c. Construction in
Combat Areas. When
Figure 6-15. Ties for erecting entanglements as seen
working in close proximity to the enemy, the
from friendly side.
necessary precautions include-
(2) Intermediate-eye tie. This tie is used
(1) Provision of security around the work
to fasten standard barbed wire to eyes other
party.
than the top eye, in screw pickets. It is made
(2) Silence.
as shown in figure 6-15. This tie and the other
(3) No working on enemy side of fence
ties described below require more time to make
unless absolutely necessary.
than the top-eye tie and each uses several cen-
(4) Use of screw pickets, if available.
timeters of wire. In making the intermediate-
(5) Men not working should lie down
eye tie shown in figure 6-15, the following
near start of work until they can continue
points are especially important:
their work.
(a) The right hand reaches over the
(6) Individual weapons must be kept
fixed wire and around the picket, with the
nearby at all times.
palm down. The left hand holds the fixed end
d. Wire Ties. Wires are tied to pickets by
for tension.
men working from the friendly side of the
(b) The loops are removed from the
wire and picket, stretching the wire with
free end and wrapped around the picket.
the right hand as the tie is started. The four
(c) One side of the loop should pass
ties used in erecting wire entanglements are
above the eye and the other side below the
shown in figure 6-13. Barbed tape is tied in
eye.
the same manner as standard barbed wire.
(3) Post tie. Standard barbed wire is
fastened to wooden pickets or to the steel U-
fasten standard barbed wire to the top eye of
shaped picket with the post tie shown in figure
screw pickets. It is made in one continuous
16 The wire should be wrapped tightly
movement of the left hand (fign 6-14) while
around the post to keep the barbs from sliding
movement of the left hand (fig. 6-14) while
the right hand exerts a pull on the fixed end of
downr With the U-shaped picket, the wire
the wire. This is a secure tie, is quickly made,
wrapping is engaged in a notch in the picket.
and uses only a short piece of wire.
The method is essentially the same as that of
the intermediate-eye tie.
6-10
AGO 2001sA
FM 5-15
right-handed man to make the ties while re-
maining faced toward the enemy.
FREE
FIXED
(2) A bar is inserted in the reel and the
reel is carried for 23 to 27 meters allowing
the wire to unreel from the bottom. This is
|MOVE FREE END
done on the friendly side of the row of pickets
PICKET
to which the wire is to be tied.
\ WITH THIS HAND E
REDE
FIXED
(3) Slack is put in the wire by moving
(
BRING WIRE UP iNTO EYE
FIXED
()
END
back toward the starting point; the ties are
FRIEE
/
,E"X'
k
then made by two men leapfrogging each other.
If available, two men can be assigned to make
the ties as the reel is unwound.
C , THREAD EYE
f. Tightening Wire. After a wire is installed
it can be tightened, if necessary, by racking
with a driftpin or short stick (fig. 6-18).
FIXED
Wires should not be racked at ties or where
AL
FREE
11
\
they intersect other wires because this makes
AROUND BACK OF EYE
END
salvage of the wire very difficult. Fences are
similarly racked to tighten them when they
sag after having been installed for some time.
END
END
Wires shodlWbe just taut enough to prevent
them from being easily depressed by boards,
mats, or similar objects thrown across them.
.1
C
O
If wires are stretched too tightly they are
FIXED END AND
more easily cut by fragments. Barbed steel
BELOW EYE
tape must never be tightened by racking.
ID JERK FREE END UP
6-7. Four-Strandl Cattle Fence
INTO EYE THUS
COMPLETING TIE
a. Description. The four-strand center sec-
tion of a double apron fence can be installed
Figure 6-14. Top-eye tie.
rapidly to obtain some obstacle effect, and
(4) Apron tie. The apron tie is used
aprons can be added later to develop it into a
whenever two wires that cross must be tied
double apron fence. In country where wire
together. It is tied in the same manner as the
fences are used by farmers, obstacles in the
post tie except that a wire is substituted for
form of four-strand cattle fences (fig. 6-19)
the post (fig. 6-17).
will blend with the landscape. Their design
(5) Barbed tape splices. Connecting slots
should follow as closely as possible the local
at each end of a 50-meter reel provide a quick
custom, usually wooden pickets at about 2- to
method of splicing reels of barbed tape.
4-pace intervals with four horizontal strands
Barbed tape may also be spliced by interlock-
of barbed wire fixed to them. They should be
ing the twisted barbs of two separate lengths,
sited along footpaths and edges of fields or
then completing the splice by twisting a short
crops, where they will not look out of place.
piece of wire to each end of the area where
If conditions permit, this fence may be im-
spliced.
proved by installing guy wires in the same
e. Method of Installing Wires.
manner as the diagonal wires of the double
(1) The end of the wire is attached to
apron fence. All longitudinal wires of this
the first anchor picket. This is the picket at
fence must start and end at an anchor picket.
the right end of a section of entanglement,
b. Construction. Eight men may be employed
from the friendly side. Fences are built from
on short sections of this fence and up to 16
right to left as this makes it easier for a
men on 300-meter sections. The two operations
AGO 20013A
611
FM 5-15
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AGO 20013A
en
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era-~~~~~~~~~~~~~~~o~os
FM 5-15
apron fence, the 4- and 2-pace fence and the
FREE
END
FIXED
END
FREE
END
FIXED END
6- and 3-pace fence. The 4- and 2-pace fence
(fig. 6-20) is the better obstacle of the two
and is the type more commonly used. In this
fence the center pickets are 4 paces apart and
the anchor pickets are 2 paces from the line
of the center pickets and opposite the midpoint
of the space between center pickets. The 6-
and 3-pace fence follows the same pattern with
AROUND PICKET OR POST
(
WRAP LOOP AROUND POST
pickets at 6- and 3-pace intervals. For this
OVER FIXED END AND TAKE
ABOVE
FIXED END
fence, less material and construction time are
LOOP FROM FREE
END
required, but the obstacle effect is substantial-
ly reduced because with the longer wire spans
it is easier to raise the lower wires and crawl
over or under them. Except for picket spacing,
FREE END
R
FIXED
END
the 4- and 2-pace and the 6- and 3-pace fences
are identical. Only the 4- and 2-pace fence
is discussed in detail.
DIAGONAL WIRE
® WRAP
LOOP AROUND FREE
FIXED END
END AT LEAST TWO TURNS
TO COMPLETE
TIE
Figure 6-16. Post tie.
FREE END
DAGONAL WRE
are laying out and installing pickets and in-
-
stalling wire.
/(
0o
(1) First operation. The working party
is divided into two groups of approximatelyFREE
END
equal size. The first group carries and lays out
DRAW AARG\
long pickets at 3-meter intervals along the
FROM SAE
centerline of the fence, beginning and ending
FEE END
WIRE
TE WIRECK
FPEE END
UNDER THE WIRE
the section with an anchor picket and includ-
B
i NRING
LOOP UP AND OVER
ing anchor pickets for guys if needed. The
THE TOP OF THE
\ DIAGONAL WIRE
second group installs the pickets.
/FXED
(2) Second operation. As the first task is
DIAGONAL WIRE
completed, men move individually to the head
\
FIXED END
of the fence and are organized into teams of
a
.
FREE END 7',
two or four men to install wires. For four-
man teams, two men carry the reel and two
men make ties and pull the wire tight. For
two-man teams, the wire must first be unrolled
for 50 to 100 meters, then the men come back
to the head of the work and make the ties,
WIRE
or the wire may first be made up into bobbins
FREE END
FIXED END
to be carried and unwound by one man while
the other man makes the ties. The first team
WIND LOOP AROUND
installs the bottom fence wire, and drawing
FREE END AT LEAST
it tight and close to the ground. Succeeding
TWO COMPLETE TURNS
teams install the next wires in order.
:
6-8.
Double-Apron Fence
a. Types. There are two types of double
Figure 6-17. Standard barbed wire apron tie.
AGO 20018A
613
FM 5-15
b. Construction. A 300-meter
section of
either type of double-apron fence is a platoon
task normally requiring 11/2 hours, assuming
36 productive men per platoon. There are two
operations in building a double apron fence:
laying out and installing pickets and instal-
ing wire. The first operation is nearly corn-
pleted prior to starting the second. The second
operation is started as men become available
and the first operation has moved far enough
ahead to avoid congestion. A platoon is nor-
Figure 6-19. Four-strand cattle fence as viewed from
mally assigned to build a 300-meter section.
the enemy side.
(1) First operation. The working party,
if not organized in three squads, is divided in-
to three groups of approximately equal size.
4 PACES
4 PACES
4 PACES
One squad lays out the long pickets along the
3m
3m -
NM
centerline of the fence at 4-pace intervals at
2 PACES'
I
lRON
the spots where they are to be installed and
I.:m
CENTER
with their points toward the enemy. Another
t
>
FENCE
squad lays out the anchor pickets, with points
2sm .REAR
toward the enemy and positioned 2 paces each
way from the centerline and midway between
PLAN
NOTE:
the long pickets (fig. 6-21). The spacing is
EYES OF ALL PICKETS POINT
readily checked with a long picket. The third
IN DIRECTION FROM WHICH
FENCE IS BEING ERECTED.
squad installs all the pickets, with the help of
the two other squads as the latter finish the
work of laying out the pickets. When installed,
, 1
70cm
the lower notch or bottom eye of the long
I
pickets should be approximately 10 cm off the
45cm
ground to make passage difficult either over
1.5m
or under the bottom wires.
CROSS SECTION
LEGEND:
1-2-3-4 ETC. INDICATES
ANCHOR PICKET
ORDER OF ERECTING WIRE.
I~i~~~e
~ISOMETRIC
VIEW
/
4 f
Figure 6-20. Double apron fence.
The order in which the wires are installed is
Figure 8.
Tightening wire by racking.
shown in figure 6-20 and is further illustrated
in figure 6-22. Care must be taken to avoid
(2) Second operation. As the groups com-
having any of the men cut off between the
plete the first operation, they return to the
fence and the enemy. The men are divided in-
head of the fence and begin installing wire.
to two- or four-man groups and proceed to
6-14
AGO 200ISA
FM 5-15
FRONT APRON
Figure 6-21. Laying out anchor pickets.
install the wires in numerical order; that is,
as soon as the men installing one wire have
moved away from the beginning of the fence
and are out of the way, the next wire is started.
Installation is as follows:
(a) The No. 1 wire is the diagonal wire
CENTER FENCE
on the enemy side and is secured with a top-
eye tie to all pickets. It is important to keep
this wire tight.
(b) The No. 2 wire is the tripwire on
the enemy side of the fence and is secured to
both diagonals just above the anchor picket
with the apron tie. This wire must be tight
enough and close enough to the ground to make
passage over or under the wire difficult.
(c) The No. 3 wire is an apron wire
on the enemy side of the fence. It
…[truncated]