BARBED WIRE ENTANGLEMENTS
Upon completion of this lesson on Barbed Wire Entanglements, you should be able to accomplish the following in the indicated topic areas:
1. Purpose. Describe the two purposes of the use of barbed wire entanglements.
2. Siting and Layout. State the 5 requirements for effective siting and layout of barbed wire entanglements.
3. Classification — by Use. Describe the 3 classes of entanglements — tactical, protective, and supplementary.
4. Classification — by Depth. Describe the 3 types of entanglements — belt, band, and zone.
5. Barbed Tape. State the advantages and disadvantages of barbed tape.
6. Material and Labor Estimates. Estimate the manhours and material needed to construct tactical, protective, and supplementary entanglements of a defensive position.
7. Uses. Describe the 7 uses of entanglements — outpost area, battle position, artillery area, reserve area, antipersonnel obstacles, roadblocks, and to strengthen material obstacles.
8. Pickets and Ties. Describe types and uses of pickets and ties.
9. Fences. Describe fences to include four strand cattle fence, double apron fence, standard concertina fence, and triple standard concertina fence.
10. Portable Barbed Wire Obstacles. Describe the portable barbed wire obstacles and their uses.
Section I. Materials
a. Purpose. Barbed wire entanglements are artificial obstacles designed to impede the movement of foot troops and, in some cases, tracked and wheeled vehicles. The materials used in constructing barbed wire entanglements are relatively lightweight and inexpensive, considering the protection they afford. Barbed wire entanglements can be breached by fire but are built rapidly, repaired, and reinforced.
b. Siting and layout. To be effective, barbed wire entanglements are sited and laid out to meet the following requirements:
(1) Under friendly observation, covered by fire, and where practicable, protected by antipersonnel mines, flame mines, tripflares, and warning devices.
(2) Concealed from enemy observation as far as practicable by incorporating terrain features such as reverse slopes, hedges, woods, paths and fence lines.
(3) Erected in irregular and non-geometrical traces.
(4) Employed in bands or zones wherever practicable.
(5) Coordinated with other elements of the defense.
c. Classification. Entanglements are classified according to their use, their depth, and whether fixed or portable.
(1) Use. Entanglements are classified by use as tactical, protective, or supplementary. The employment of these types in a defensive area is shown schematically in figure 4-1.
(a) Tactical. Tactical wire entangle-ments are sited parallel to and along the friendly side of the final protective line. They are used to break up enemy attack formations and to hold the enemy in areas covered by the most intense defensive fire. Tactical entanglements extend across the entire front of a position but are not necessarily continuous.
(b) Protective. Protective wire entanglements are located to prevent surprise assaults from points close to the defense area. As in the case of all antipersonnel obstacles, they are close enough to the defense area for day and night observation and far enough away to prevent the enemy from using hand grenades effectively from points just beyond the obstacle, normally 40 to 100 meters (131 to 328 ft.). Protective wire surrounds the individual units of a command, usually the platoons (fig 4-2). These entanglements should be connected to entanglements around other platoons by supplementary wire to enclose the entire defensive positions. Protective entanglements are erected around rear-area installations in the same manner and to serve the same purpose as protective wire around defensive positions in forward areas. Protective wire also includes the entanglements which should be installed over the tops of installations provided with overhead cover (fig 4-2).
Figure 4-1. Schematic layout of barbed wire entanglements in a defensive area.
Figure 4-2. Protective wire on top of overhead cover.
(c) Supplementary. Supplementary wire entanglements in front of the forward edge of the battle area are used to conceal the exact line of the tactical wire. To the rear of the FEBA, supplementary wire is used to enclose the entire defensive position by connecting the protective wire entanglements. Supplementary wire entanglements used to break up the line of tactical wire should be identical to the tactical wire entanglements and constructed simultaneously with them whenever possible.
(2) Depth. Entanglements are classified by depth as belts, bands, or zones.
(a) Belt. A belt is an entanglement one fence in depth.
(b) Band. A band consists of two or more belts in depth, with no interval between them. The belts may be fences of the same type, or the band may be composed of two or more fences of different types.
(c) Zone. A zone consists of two or more bands or belts in depth, with intervals between them.
(3) Equivalent effectiveness. Entanglement depths are also described or specified in terms of comparative effectiveness. Tactical wire entanglements should be equivalent in effectiveness to three belts of 4- and 2-pace double apron fence whenever possible. Protective wire may employ any type of entanglement provided its effectiveness is at least the equivalent of that of the 4- and 2-pace double apron fence. Supplementary wire should have an effectiveness equivalent to that of the type of wire it supplements. It should be equivalent to tactical wire or equivalent to the type of protective wire being used if it connects the outer perimeters of protective wire at the flanks and rear.
(a) Fixed entanglements are those types which must be erected in place and which cannot be moved unless completely disassembled.
(b) Portable entanglements are those types which can be moved without complete disassembly. Portable entanglements have been developed for one of the following reasons: To permit assembly in rear areas, with ease of transportation and rapid installation in forward positions. For the temporary closing of gaps or lanes which can be reopened quickly for patrols or counterattacking forces.
d. Lanes and gaps. Lanes and gaps are provided for the passage of patrols, working parties, and attacking or counterattacking forces. When not in use they are kept closed by the use of portable obstacles covered by fire. In barbed wire zones, lanes and gaps are staggered in a zigzag pattern.
(1) Outpost area. Combat outposts should be surrounded with wire entanglements. These entanglements should be carefully sited to serve as both protective and tactical wire and must be covered by small arms fire. The wire obstacle should be supplemented by antipersonnel mines, warning devices, and booby traps.
(2) Battle position. In the battle area, each company defense position is normally surrounded by a wire entanglement which is connected laterally across the front to the entanglements surrounding the other units in the position.
(3) Artillery and reserve area. Wire entanglements are used in the outer protection of howitzer positions. Heavier weapons, and shelters or other installations in the reserve area, are similarly protected if justified by the situation.
(4) Antipersonnel obstacles. Barbed wire entanglements, tripflares, noisemakers, and antipersonnel mines are sited to warn against enemy patrol action or infiltration at night; to prevent the enemy from delivering a surprise attack from positions close to the defenders; and to hold, fix or delay the enemy in the most effective killing ground. Such obstacles should be near enough to defensive positions for adequate surveillance by the defenders by night and day and far enough away to prevent the enemy from using hand grenades against the defender from points just beyond the obstacles.
f. As roadblocks. A series of barbed wire concertinas as shown in
figure 4-3 will stop wheeled vehicles. A series of these concertinas should be placed in blocks about 10 meters in depth. The ends of adjacent coils are wired together and the obstacle lightly anchored at the sides of the road. The block should be sited to achieve surprise.
g. To strengthen natural obstacles. Deep rivers, canals, swamps, and cliffs which form effective delaying obstacles to infantry, and thick hedgerows, fences, and woods, which are only partial obstacles, can be improved by lacing with barbed wire, by the addition of parts of standard fences on one or both sides, or by entangling with loose wire.
Figure 4-3. Concertina roadblock.
4-2. STANDARD BARBED WIRE
a. Description. Standard barbed wire is 2-strand twisted No. 12 steel wire with 4-point barbs at 10 cm (4 in.) spacing (fig 4-4).
b. Handling. In handling barbed wire, the standard barbed wire gauntlets shown in figure 4-4 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 4-5) containing about 400 meters (1312 ft.) of wire. The wire weighs 40.8 kg (90 lb.) and the reel 0.6 kg. In building a fence, two men carry one reel.
d. Bobbins. Bobbins (fig 4-6) holding about 30 meters (98 ft.) of wire are prepared, normally in 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. Two or more men may make the bobbins as follows:
Figure 4-4. Standard barbed wire.
Figure 4-5. Barbed wire reel.
Figure 4-6. Barbed wire bobbin.
(1) The bobbin sticks are prepared.
(2) The reel is rigged on a improvised trestle or other support.
(3) One man unrolls and cuts 30-meter (98 ft.) lengths of wire. One end of each piece is fastened to the trestle.
(4) The wire is wound in figure-eight shape on the bobbin sticks.
(5) A piece of white tracing tape should be tied to the loose end of the wire to facilitate finding it.
4-3. BARBED STEEL TAPE
a. Characteristics. The physical characteristics of barbed tape (fig. 4-7) are as follows:
Width: 3/4 inch (1.91 cm)
Thickness: 0.222 (.056 cm)
Weight: 4.438 lb/50 meters (/164 Ft)
Width of barb: 7/16 inch (1.11 cm)
Interval between barbs: l/2 inch (1.25 cm)
Breaking load: 500 lb. (1111 kg)
b. Handling. In handling barbed tape, heavy barbed tape gauntlets should be used instead of the standard gauntlets. Small metal clips on the palm and fingers prevent the barbs of the tape from cutting the leather (fig. 4-8). The light weight of the barbed tape and compactness, it is much easier to handle, store, and transport than barbed wire.
c. Issue. Barbed tape is issued in 50-meter (164 ft.) reels weighing 2.4 kg. There are six reels to a cardboard carrying case.
d. Barbed tape dispenser. A dispenser (fig. 4-8) is required to install barbed tape. It consists of a frame to hold the 50-meter (164 ft.) reel of barbed tape and two sets of rollers. The reel is inserted on the spindle and the tape is threaded through the two sets of parallel rollers. The outside set of rollers are then turned 90° in a clockwise direction. The hinged arm of the frame is then closed and locked in place by the frame of the rotating rollers. As the tape unwinds from the reel, the two sets of rollers oriented 90° to each other impart a twist to the tape. To be effective the barbed tape must be twisted as it is installed.
Figure 4-7. Barbed steel tape.
Two significant characteristics shown above which are important to field users are the weight and the breaking load. A comparison of pertinent characteristics of barbed tape and barbed wire is shown below.
e. Uses. Barbed tape can be used in place of standard barbed wire in most all cases except when it is to be repeatedly recovered and reused. The most effective fence that can be constructed using barbed tape is the double-apron fence.
(1) The principal advantages of barbed tape are its size and weight. For equal lengths, barbed tape occupies a third of the space and weighs a third as much as standard barbed wire. A double-apron fence constructed with barbed tape is more difficult to breach by crawling through than one constructed with standard barbed wire because the barbs of the barbed tape are closer together. Because of the flat configuration, it is more difficult to cut barbed tape with wire cutters.
(2) At the present time, the major disadvantage of barbed tape is the breaking strength. Standard barbed wire is twice as strong. Installation of barbed tape requires a dispenser. A major problem could arise if the dispenser is not available. The tape is not recoverable to its original condition. However, it may be recovered on bobbins in the twisted condition. Barbed tape is more easily cut by shell fragments than standard barbed wire. Barbed tape can also be cut with a bayonet.
Figure 4-8. Barbed tape equipment.
f. Double-apron fence. The standard double-apron fence is one of the best obstacles that can be made with barbed tape; and the effectiveness of this obstacle is increased by —
(1) Raising the top wire to preclude crossing the obstacle by stepping over it.
(2) Placing low wires 4 inches above ground to prevent personnel from crawling under the obstacle.
g. Tying procedures. In tying barbed tape the wrap-around tie (fig. 4-7) should be used, since the sharp bends of other ties weaken the tape. Steel wire rings, crimped on, provide effective ties and may be used where available (fig. 4-8).
h. Splices. Connecting slots at each end of a 50-meter (164 ft.) reel provide a quick method of splicing reels of barbed tape (fig. 4-9). Barbed tape may also be spliced by interlocking the twisted barbs of two separate lengths, then completing the splice by affixing one steel wire ring to each end of the area where spliced
Figure 4-9. Splicing barbed steel tape.
Wire entanglements are supported on metal or wood pickets.
a. Metal pickets. Metal pickets are issued in two types, screw and U-shaped. The standard lengths are short or anchor, medium, and long (fig. 4-10). The U-shaped picket also comes in an extra long length. Pickets that are serviceable are recovered and used again.
(1) Screw picket. The screw picket is screwed into the ground by turning it in a clockwise direction using a driftpin, stick, or another picket inserted in the bottom eye of the picket for leverage. The bottom eye is used in order to avoid twisting the picket. Screw pickets are installed so the eye is to the right of the picket, as seen from the friendly side
so standard ties to be made easily. Screw pickets tend to be less rigid than other types but are desirable because they can be installed rapidly and silently. When silence is necessary, the driftpin used in installing the pickets should be wrapped with cloth.
Figure 4-10. Pickets for use with barbed wire.
(2) U-shaped picket. 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 sledge hammer. A stake driving cap is used on top of the picket to prevent a sledge from deforming it. Driving the pickets is noisier than installing screw pickets. Noise may be reduced 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 where noise is not a disadvantage and time is available. The pickets are driven with the hollow surface or concave side facing enemy fire because small arms projectiles ricochet from the convex side. An expedient picket driver which can be locally fabricated is shown in figure 4-11. Constructed as shown it weighs approximately 12 kilograms and is operated by two men. One man holds the picket in a vertical position while the other slides the driver over the picket and starts it into the ground. Then, both men work the picket driver up and down until the required depth is reached. Short pickets can be driven by turning the picket driver upside down and using the head as a hammer. The bucket of a front loader can be used to push U-shaped pickets into the ground if the tactical situation permits the use of equipment.
Figure 4-11. Expedient picket driver.
(3) Arctic adapter. For erecting barbed wire obstacles with U-shaped drive pickets under conditions where frozen ground prevents driving the pickets, an Arctic adapter is available for anchoring the pickets. The adapter is made of steel and consists of a base plate equipped with an adjustable channel receptacle and two anchor pins. It is anchored by driving the anchor pins through holes in the base place into the ground. One anchor pin drive sleeve with driving pin is provided with each 20 adapters to facilitate anchor pin emplacement. When adapters are not available, a hole can be started with a pick and the picket can be frozen in place by pouring water and snow into the hole.
b. Wooden picket. Expedient wooden pickets of several types may be used.
(1) Round poles 10 cm (4 in.) 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 the wire from sliding on the picket and to simplify camouflage. Longer pickets are required in loose or sandy soil or when driving through a snow cover. The driving of wooden pickets is not as noisy as the driving of steel pickets, and the noise can be reduced further by fastening a section of tire tread over the face of the hammer or maul. For driving in hard earth, picket tops are wrapped with wire to avoid splitting. Pickets of hardwood, properly installed, are sturdy and rigid.
(2) Dimension lumber ripped to a square cross section may be used instead of round poles. This is equally satisfactory except that is more difficult to camouflage. Such pickets may be camouflaged by painting prior to driving.
(3) Standing trees and stumps may be used as pickets when their location permits.
c. Reference. Table 4-1 lists information pertaining to materials used in the construction of barbed wire entanglements.
4-5. CONCERTINA FENCING
a. Standard barbed wire concertina. The standard barbed wire concertina (fig. 4-12) is a commercially manufactured barbed wire obstacle made of a roll of single-strand, high-strength, spring-steel wire with 4-point barbs attached at 5 cm (2 in.) spacing. Wires forming the coils are clipped together at intervals so the concertina opens to a cylindrical shape 5 to 15 meters (16.4 to 49.2 ft.) long (depending on structure and build of opening) and 90 centimeters (3 ft.) in diameter. The 5-meter (16.4 ft.) length prevents smaller enemy personnel from crawling through the wire as the coils are closer together. Tanglefoot should also be employed in conjunction with the wire to further increase the barrier's effectiveness. The concertina is easily opened and collapsed and can be used repeatedly because the wire returns to its original shape after a crushing force is applied and then removed. The wire is much harder to cut than standard barbed wire. The concertina weighs 25.4 KG (55.8 lb).
Table 4-1. Wire and Tape Entanglement Materials
Figure 4-12. Standard barbed wire concertina.
(a) To open concertina. The collapsed concertina is tied with plain wire bindings attached to the quarter points of a coil at one end of the concertina. In opening the concertina, these bindings are removed and twisted around the carrying handle for use in tying the concertina when it is again collapsed. Four men open a concertina and extend it to the 5- to 15-meter (16.4 to 49.2 ft.) length, with one man working at each end and others spaced along its length to insure it opens and extends evenly. When necessary, two men can easily open a concertina by bouncing it on the ground to prevent snagging as they open it.
(b) To collapse concertina. Two men can collapse a concertina in the following manner: First all kinks in coils are removed. Loose clips are then tightened or replaced with plain wire. To close the concertina, one man stands at each end of it and places a foot at the bottom of the coil and an arm under the top of the coil. The two men walk toward each other closing the concertina by feeding the wire over their arms and against their feet. When closed, the concertina is laid flat and compressed with the feet. The concertina is tied with plain wire bindings.
(c) To carry concertina. One man easily carries the collapsed concertina by stepping into it and picking it up by the wire handles attached to the midpoints of an end coil.
(2) Staples. Improvised staples approximately 45 cm (18 in.) long and made of l/2 inch (1.25 cm) driftpins or similar material are used to fasten the bottoms of concertina fences securely to the ground.
b. Barbed steel tape concertina. Barbed tape concertina comes in a diameter of 85 cm (33 in.) and an expanded length of 15.2 meters (50 ft.). It is formed of barbed tape wrapped around a high strength, spring steel, core wire. Its configuration, method of handling, and method of employment are similar to standard barbed wire concertina. One roll weighs only 14 kg (31 lbs.).
Section II. Construction Procedures
4-6. Organization of Work
Table 4-2 gives the materials and manhours required for entanglements of the various types. The normal sizes of work crews are given in the descriptions of the entanglements. For each construction project, the senior noncommissioned officer divides his crew into groups of approximately equal size, based on his knowledge of the skill and speed of each man. He organizes them in such a way that construction proceeds in proper order and at a uniform rate. Each individual must know exactly what his group isto do and his particular job in the group. Each man should have barbed wire gauntlets. The sequence of operations for each fence is given in the paragraph describing the erection of the fence. The sequence that is outlined should be followed, and as experience is gained, the size and composition of the groups may be varied. For each section of entanglement, all fence-building operations normally proceed from right to left, as one faces the enemy. It may be necessary under some circumstances to work from left to right. If time permits, men should be taught to work in either direction. In case of heavy casualties, the senior officer or NCO will decide what wires, if any, are to be omitted.
Table 4-2. Material and Labor Requirements for 300 Meter Sections of Various Wire Entanglements.
a. Construction at night. For night construction the following additional preparations are made:
(1) Tracing tape should be laid from the materials dump to the site of work and then along the line of fence where possible.
(2) Materials should be tied together in man loads, and pickets bundled tightly to prevent rattling.
(3) Wire fastenings of wire coils and pickets should be removed and replaced with string which can be broken easily.
(4) A piece of tape should be tied to the ends of the wire on each reel or bobbin.
b. Supervision. Proper supervision of entanglement construction includes the following:
(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 overcrowding of personnel.
(4) Making sure the wires are tightened properly and spaced correctly.
(5) Checking ties to verify that they are being made correctly and at the right points.
c. Construction in combat areas. When working in close proximity to the enemy, the necessary precautions include—
(1) Provision of security around the work party.
(3) No working on enemy side of fence unless absolutely necessary.
(4) Use of screw pickets, if available.
(5) Men not working should seek concealment near the work site until they begin work.
(6) Individual weapons must be kept nearby at all times.
d. Wire ties. Wires are tied to pickets by men working from the friendly side of the wire and picket; the wire is stretched with the right hand as the tie is started. The four ties used in erecting wire entanglements are shown in figure 4-13.
Figure 4-13. Ties for erecting entanglements as seen from the friendly side.
(1) Top-eye tie. The top eye is used to fasten standard barbed wire to the top eye of screw pickets. It is made in one continuous movement of the left hand (fig 4-14) while the right hand exerts a pull on the fixed end of the wire. This is a secure tie, quickly made, and uses only a short piece of wire.
Figure 4-14. Top-eye tie.
(2) Intermediate-eye tie. This tie is used to fasten standard barbed wire to eyes other than the top eye, in screw pickets. It is made as shown in figure 4-15. This tie and the other ties described below require more time to make than the top-eye tie and each uses several centimeters of wire. In making the intermediate-eye shown in figure 4-15, the following points are especially important:
(a) The right hand reaches over the fixed wire and around the picket, with the palm down. The left hand holds the fixed end for tension.
(b) The loops are removed from the free end and wrapped around the picket.
(c) One side of the loop should pass above the eye and the other side below the eye.
(3) Post tie. Standard barbed wire is fastened to wooden pickets or to the steel U-shaped picket with the post tie shown in figure 4-16. The wire should be wrapped tightly around the post to keep the barbs from sliding down. With the U-shaped picket, the wire wrapping is engaged in a notch in the picket. The method is essentially the same as that of the intermediate-eye tie.
(4) Apron tie. The apron tie is used whenever two wires that cross must be tied together. It is tied in the same manner as the post tie except a wire is substituted for the post (fig. 4-17).
(5) Barbed tape splices. Connecting slots at each end of a 50-meter (164 ft.) reel provide a quick method of splicing reels of barbed tape. Barbed tape may also be spliced by interlocking the twisted barbs of two separate lengths, then completing the splice by twisting a short piece of wire to each end of the area where spliced.
e. Method of installing wires
(1) The end of the wire is attached to the first anchor picket. This is the picket at the right end of a section of entanglement, from the friendly side. Fences are built from right to left as this makes it easier for a right-handed man to make the ties while remaining faced toward the enemy.
(2) A bar is inserted in the reel and the reel is carried for 23 to 27 meters (75 to 88 ft.), allowing the wire to unwind from the bottom of the reel. This is done on the friendly side of the row of pickets to which the wire is to be tied.
(3) Slack is put in the wire by moving back toward the starting point; the ties are then made by two men leapfrogging each other. If available, two men can be assigned to make the ties as the reel is unwound.
f. ;Tightening wire. After a wire is installed it can be tightened, if necessary, by racking with a driftpin or short stick (fig. 4-18). Wires should not be racked at ties or where they intersect other wires because this makes salvage of the wire very difficult. Fences are similarly racked to tighten them when they sag after having been installed for some time. Wires should be just taut enough to prevent them from being depressed easily by boards, mats, or similar objects thrown across them. If wires are stretched too tightly they are more easily cut by fragments. Barbed steel tape must never be tightened by racking.
Figure 4-15. Intermediate-eye tie.
Figure 4-16. Post tie.
4-7. FOUR-STRAND CATTLE FENCE
a. Description. The four-strand center section of a double apron fence can be installed rapidly to obtain obstacle effect, and aprons can be added later to develop it into a double apron fence. In rural areas where wire fences are used by farmers, obstacles in the form of four-strand cattle fences (fig. 4-19) will blend with the landscape. Their design should follow as closely as possible the local custom, usually wooden pickets at about 2- to 4-pace intervals with four horizontal strands of barbed wire fixed to them. They should be sited along footpaths and edges of fields or crops, where they will not look out of place. If conditions permit, this fence may be improved by installing guy wires in the same manner as the diagonal wires of the double apron fence. All longitudinal wires of this fence must start and end at an anchor picket.
b. Construction. Eight men may be employed on short sections of this fence up to 16 men on 300-meter (984 ft.) sections.
Figure 4-17. Standard barbed wire apron tie.
Figure 4-18. Tightening wire by racking.
The two operations are laying out and installing pickets, and installing wire.
(1) First operation. The work party is divided into two groups of approximately equal size. The first group carries and lays out long pickets at 3-meter (9.8 ft.) intervals along the centerline of the fence, beginning and ending the section with an anchor picket, and including anchor pickets for guys if needed. The second group installs the pickets.
Figure 4-19. Four-strand cattle fence as viewed from the enemy side.
(2) Second operation. As the first task is completed, men move individually to the head of the fence and are organized into teams of two or four men to install wires. Four 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 (164 to 328 ft.), then the men come back to the head of the work and make the ties or the wire may first be made up into bobbins to be carried and unwound by one man while the other man makes the ties. The first team installs the bottom fence wire, and draws it tight and close to the ground. Succeeding teams install the next wires in order.
4-8. DOUBLE-APRON FENCE
a. Types. There are two types of double apron fence, the 4- and 2-pace fence and the 6- and 3-pace fence. The 4- and 2-pace fence (fig. 4-20) 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 pickets at 6- and 3-pace intervals. For this fence, less material and construction time are required, but the obstacle effect is substantially reduced because with the longer wire spans make it is easier to raise or lower the wires and crawl over or under them. Except for picket spacing, 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.
Figure 4-20. Double apron fence.
b. Construction. A 300-meter (984 ft.) section of either type of double-apron fence is a platoon task normally requiring 1 l/2 hours, assuming 36 productive men per platoon. There are two operations in building a double apron fence: laying out and installing pickets, and installing wire. The first operation is nearly completed 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 normally assigned to build a 300-meter (984 ft.) section.
(1) First operation. The work party, if not organized in three squads, is divided into three groups of approximately equal size. One squad lays out the long pickets along the centerline of the fence at 4-pace intervals at the spots where they are to be installed and with their points toward the enemy. Another squad lays out the anchor pickets, with points toward the enemy and positioned 2 paces each way from the centerline and midway between the long pickets (fig. 4-21). The spacing is readily checked with a long picket. The third 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, the lower notch or bottom eye of the long pickets should be approximate 10 cm (4 in.) off the ground to make passage difficult either over or under the bottom wires.
Figure 4-21. Laying out anchor pickets.
(2) Second operation. As the groups complete the first operation, they return to the head of the fence and begin installing wire. The order in which the wires are installed is shown in figure 4-20 and is further illustrated in figure 4-22. Care must be taken to avoid having any of the men cut off between the fence and the enemy. The men are divided into two- or four-man groups and proceed to 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 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 trip wire 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.
Figure 4-22. Sequence of installing wire in a double apron fence.
(c) The No. 3 wire is an apron wire on the enemy side of the fence. It is secured to the first diagonal wire, and thereafter to each alternate diagonal, and then to the last diagonal wire. The No. 4 wire is also an apron wire on the enemy side of the fence. It is secured to the first diagonal wire (No. 1), thereafter to the diagonal wires which are not tied to the No. 3 wire, and then to the last diagonal wire. Apron wires Nos. 3 and 4 are equally spaced along the diagonal wire.
(d) The No. 5 wire is the first one which is not started from the end anchor picket. It is started at the first long picket, and ended at the last long picket. It is secured with the intermediate-eye tie and is stretched tightly to prevent passage over or under it.
(e) Wires No. 6, 7, and 8 complete the center portion of the fence and are secured to the long picket No. 6 and 7 with the intermediate-eye tie. They also start at the first and end at the last long picket. No. 8 is secured with the top-eye ties. These wires (No. 6, 7, and 8) for the backbone of the fence and are drawn up tightly to hold the pickets in position.
(f) No. 9 is the diagonal apron wire on the friendly side of the fence and is secured with the top-eye to all pickets. No. 10 and 11 are apron wires and No. 12 is the tripwire on the friendly side of the fence. Wire No. 12 is installed in the same manner as wire No. 2 (b) above).
(g) If the fence is not satisfactorily tight when installed, wires are tightened by racking as described in paragraph 4-6f.
4-9. STANDARD CONCERTINA FENCES
As an obstacle, in most situations, the triple standard concertina fence is better than the double apron fence. The material for the standard concertina fence weighs about 50 percent more than for a triple standard concertina fence of the same length, but it is erected with about one-half the man-hours. Every concertina fence is secured firmly to the ground by driving staples at intervals not more than 2 meters (6.6 ft.). The staples are used on the single concertina fence and on the front concertina of the double and triple types. The two types of fence are as follows:
a. Single concertina. This is one line of concertinas. It is erected quickly and easily but is not an effective obstacle in itself. It is used as emergency entanglement or for the temporary closing of gaps between other obstacles. It is for such purposes that one roll of concertina may be habitually carried on the front of each vehicle in combat units.
b. Double concertina. This consists of a double line of concertinas with no interval between lines. The two lines are installed with staggered joints. As an obstacle, the double concertina is less effective than a well-emplaced, double apron fence. It is used in some situations to supplement other obstacles in a band or zone.
4-10. TRIPLE STANDARD CONCERTINA FENCE
a. Description. This consists of two lines of concertinas serving as a base, with a third line resting on top, as shown in figure 4-23. All lines are installed with staggered joints. Each line is completed before the next is started so a partially completed concertina entanglement presents some obstruction. It is erected quickly and is difficult to cross, cut, or crawl through.
Figure 4-23. Triple standard concertina fence.
b. Detail. A 300-meter (984 ft.) section of this fence is a platoon task normally requiring less than 1 hour. There are two operations: carrying and laying out pickets and concertina rolls and installing pickets, and opening and installing concertinas.
c. First operation. For the first operation, the work party is divided into three groups of approximately equal size: one to lay out all pickets, one to install all pickets, and one to lay out all concertina rolls.
(1) The first group lays out front row long pickets at 5 pace intervals on the line of fence (fig. 4-24) with points of pickets on line and pointing toward the enemy. The rear row long pickets are laid out on a line 90 cm (3 ft.) to the rear and opposite the center of interval between the front row long pickets. An anchor picket is laid out at each end of each line, 1.5 meters (5 ft.) from the end long picket.
Figure 4-24. Laying out long pickets for triple concertina fence.
(2) The second group installs pickets beginning with the front row
(fig. 4-25). As in other fences, eyes of screw pickets are to the right. Concave faces of U-shaped pickets are toward the enemy.
Figure 4-25. Installing front row pickets for triple concertina fence.
(3) The third group lays out concertinas along the rows of pickets (fig. 4-26). In the front row, one roll is placed at the third picket and one at every fourth picket thereafter. Sixteen staples accompany each front row concertina. In the second row, two rolls are placed at the third picket and two at every fourth picket thereafter. As each roll is placed in position, its binding wires are unfastened but are left attached to the hoop at one end of the roll.
Figure 4-26. Laying out concertina.
d. Second operation. As they complete the first operation, all men are organized in four-man parties (fig. 4-27) to open and install concertinas, beginning at the head of the fence. The sequence, shown in general in figure 4-27 is as follows:
(1) Open the front row concertinas in front of the double line of pickets and the other two in its rear.
(2) Lift each front row concertina in turn and drop it over the long pickets, then join concertina ends as shown in figure 4-28.
(3) Fasten the bottom of the concertina to the ground by driving a staple over each pair of end hoops, one over the bottom of a coil at each long picket, and one at the l/2 and l/4 points of the 3.8-meter (12.5 ft.) picket spacing. Securing the front concertina to the ground is essential and must be done before installing another concertina in its rear unless the enemy side of the entanglement is sure to be accessible later.
Figure 4-27. Installing concertina.
Figure 4-28. Joining concertina.
(4) Stretch a barbed wire strand along the top of each front row and fasten it to the tops of the long pickets, using the top eye tie for screw pickets. These wires are stretched as tightly as possible to improve the resistance of the fence against crushing.
(5) Install the rear row concertina as described above for the front row concertina.
(6) Install the top row concertina (fig. 4-27), fastening the end hoops of 15-meter (50 ft.) sections with plain steel wire ties. Begin this row at a point between the ends of the front and rear of the lower rows, thus breaking all end joints.
(7) Rack the top concertina to the rear horizontal wire at points halfway between the long pickets. If there is safe access to the enemy side of the fence, similarly rack the top concertina to the forward horizontal wire.
4-11. LOW-WIRE ENTANGLEMENT
a. General. This is a 4- and 2-pace double apron fence in which medium pickets replace long pickets in the fence centerline (fig. 4-29). This results in omission of the Nos. 6, 7, and 8 wires, and in bringing all the apron and diagonal wires much closer to the ground so passage underneath this fence is difficult. This fence may be used advantageously on one or both sides of the double apron fence. The low wire entanglement is used where concealment is essential. In tall grass or shallow water, this entanglement is almost invisible and is particularly effective as a surprise obstacle. However, a man can pick his way through this low wire fence without much difficulty; therefore, for best results it must be employed in depth.
Figure 4-29. Low wire fence.
b. Construction. Except for the omission of three wires and the substitution of the medium pickets, this fence is constructed in the same manner as the double apron fence.
4-12. High-wire Entanglement
a. Description. This obstacle consists of two parallel 4-strand fences with a third 4-strand fence zigzagged between them to form triangular cells. With two rows of pickets as shown in figure 4-30, the entanglements is classed as a belt; with one or more additional rows of fences and triangular cells it is a band. To add to the obstacle effect, front and rear aprons may be installed and spirals of loose wire may be placed in the triangular cells.
Figure 4-30. High wire entanglement.
b. Construction. A 300-meter (984 ft.) section of high entanglement with two rows of pickets, as shown in figure 4-30, is a platoon task normally requiring about two hours, assuming 38 men per platoon. The two operations are: laying out and installing pickets, and installing wire.
(1) First operation. For this operation the working party is divided into two groups, two-thirds of the men going to the first group and one-third to the second. The first group carries and lays out pickets, front row first and at 3-meter (10 ft.) intervals. Second row pickets are laid out in a line 3 meters (10 ft.) to the rear of the front row and spaced midway between them. The first group also lays out an anchor picket in line with each end of each 4-strand fence, 3 meters (10 ft.) from the nearest long picket. If guys are needed, anchor pickets are also laid out in lines 2 paces from the lines of the front and rear fences, opposite and midpoint of spaces between the long pickets. The second group installs front row pickets, returns to the head of the fence, installs the rear row, and then installs the anchor pickets. When the first group finishes laying out pickets, they begin installing wire and help finish installing the pickets.
(2) Second operation. As the first task is completed, men move individually to the head of the fence and are organized into teams of two or four men to install wires in the same manner as for the 4-strand fence. The order of installation is as shown in figure 4-30, except if front guys are used they are installed before the No. 1 wire; rear guys after the No. 12 wire. The lengthwise wires of each 4-strand fence begin and end at an anchor picket.
4-13. TRESTLE APRON FENCE
The trestle apron fence (fig. 4-31) has inclined crosspieces spaced at 4.8- to 6-meter (15.7 - 19.7 ft.) intervals to carry longitudinal wires on the enemy side. The rear ends of the crosspieces are carried on triangular timber frames which are kept from spreading by tension wires on the friendly side. The crosspiece may be laid flat on the ground for tying the longitudinal wires in place and then raised into position on the triangular frames. The frames are tied securely in place and held by the tension wires. The fence should be sited in such a way it can be guyed longitudinally to natural anchorages and racked tight.
Figure 4-31. Trestle apron fence.
Figure 4-32. Lapland fence.
4-14. LAPLAND FENCE
Figure 4-32 shows the lapland fence which can be used equally well on frozen or rocky ground, and on bogs or marshlands. This fence is wired with six strands of barbed wire on the enemy side, four strands on the friendly side, and four strands on the base. In snow, the tripods can be lifted out of the snow with poles or other means to reset the obstacle on top of newly fallen snow. On soft ground, the base setting of tripods and the base wires give enough bearing surface to prevent the obstacle from sinking.
4-15. PORTABLE BARBED WIRE OBSTACLES
Standard concertinas are readily moved and are well adapted for the temporary closing of gaps or lanes, or for adding rapidly to the obstacle effect of fixed barriers such as the double apron fence. Other portable barbed wire obstacles are described below.
a. Spirals of loose wire. By filling open spaces in and between wire entanglements with spirals of loose wire, the obstacle effect is substantially increased. Spirals for such use are prepared as follows:
(1) Drive four 1-meter (3.3 ft.) posts in the ground to form a diamond 1 by l/2-meter (3.3 by 1.6 ft.).
(2) Wind 75 meters (246 ft.) of barbed wire tightly around the frame. Start winding at bottom and wind helically toward top.
(3) Remove wire from frame and tie at quarter points for carrying or hauling to site where it is to be opened and used. One spiral weighs less than 9.1 kg (20 lbs.) and a man can carry three or more of them by stepping inside the coils and using wire handles of the type furnished with the standard concertina.
(4) If spirals are needed in large quantities, mount the diamond-shaped frame on the winch of a truck and use the winch to coil the wire.
b. Knife rest. The knife rest (fig. 4-33) is a portable wooden or metal frame strung with barbed wire. It is used wherever a readily removable barrier is needed; for example, at lanes in wire obstacles or at roadblocks. With a metal frame it can be used as an effective underwater obstacle in beach defenses. Knife rests are normally constructed with 3 to 4 meters (9.8 to 16.4 ft.) between cross members. They should be approximately 1 meter (3.3 ft.) high. The cross members must be firmly lashed to the horizontal member with plain wire. When placed in position, knife rests must be securely fixed.
Figure 4-33. Knife rest.
c. Trip wires. Immediately after a defensive position is occupied and before an attempt is made to erect protective wire, trip wires should be placed just outside of grenade range, usually 30 to 40 meters (98 to 131 ft.). These wires should stretch about 23 centimeters (9 in.) above the ground and be fastened to pickets at not more than 5-meter (16.4 ft.) intervals. They should be concealed in long grass or crops on a natural line such as the side of a path or the edge of a field. The Trip wires should be placed in depth in an irregular pattern.
d. Tanglefoot. Tanglefoot (fig. 4-34) is used where concealment is essential and to prevent the enemy from crawling between fences and in front of emplacements. The obstacle should be employed in a minimum depth of 10 meters (32.8 ft.). The pickets should be spaced at irregular intervals of from 75 cm to 3 meters (2.5 to 10 ft.), and the height of the barbed wire should vary between 23 to 75 cm (9 to 30 in.). Tanglefoot should be sited in scrub, if possible, using bushes as supports for part of the wire. In open ground, short pickets should be used. Growth of grass should be controlled to help prevent the enemy from secretly cutting lanes in, or tunneling under, the entanglement.
Figure 4-34. Tanglefoot in barrier system.
4-16. COMBINATION BANDS
As noted in paragraph 4-12, the high wire entanglement may be built with additional rows of fences and triangular cells to form bands of any desired depth or may be made more effective by adding front and rear aprons. Other types of fences may be combined in bands to form obstacles which are more difficult to breach than a single belt. Portable barbed wire obstacles may be added as described in paragraph 4-15. The construction of bands of varied types is desirable because this makes it difficult for the enemy to develop standard methods of passage and it permits fitting the obstacles to the situation and to the time and materials available. Six different types of effective combination bands are shown in figure 4-35. Other variations are readily developed.
Figure 4-35. Combination bands of wire obstacles.
Section III. Material and Labor Estimates
4-17. BASIC CONSIDERATIONS
Barbed wire obstacles are constructed primarily from issue materials, thus, both logistical and construction estimates are involved. Table 4-1 gives weights, lengths, and other data required for estimating truck transportation and carrying party requirements. Table 4-2 gives the material and labor requirements for construction of various wire entanglements.
4-18. Requirements for a Defensive Position
a. When estimating materials and labor requirements for wire entanglements deployed along the FEBA, use the following rules of thumb to determine the effective length of the entanglement:
(1) Tactical wire: Front x 1.25 x number of belts.
(2) Protective wire: Front x 5 x number of belts.
(3) Supplementary wire:
(a) Forward of FEBA: Front x 1.25 x number of belts.
(b) Rear of FEBA: Unit depth x 2.5 x number of belts.
b. When estimating material and labor requirements for wire entanglements deployed around a perimeter defensive position, use the following rules of thumb to determine the effective length of the entanglements.
(1) Tactical wire: Mean perimeter of the wire x 1.25 x number of belts.
(2) Protective wire: Mean perimeter of the wire x 1.10 x number of belts.
(3) Supplementary wire: Mean perimeter of the wire x 1.25 x number of belts.
c. Method of estimating. The following step- by-step procedure is recommended for estimating material, labor, and transportation requirements for various lengths and types of wire entanglements.
(1) Determine the employment by use, whether Tactical, Protective, or Supplementary wire will be constructed.
(2) Determine the depth of employment by totaling the number of belts of wire.
(3) Determine the effective length of the entanglement by utilizing the appropriate rule of thumb in a or b above.
(4) In order to utilize table 4-3 to determine the quantities of material and the manhours required for construction, the effective length must be divided by 300. This gives you the number of 300 meter sections you would effectively construct. Carry this number out two decimal places and then round-off to the nearest tenth.
(a) Multiply the number of 300 meter sections times the values in table 4-3 according to the type of wire to be constructed. Pay careful attention to the footnotes for this table. You may have more than one choice of values and various factors may be required to adjust the table values.
(b) The number of 300 meter sections is multiplied by the appropriate value in each column of table 4-2, except for the column entitled Kilograms of materials per linear meter of entanglement. The value in this column is the average weight per meter and should be multiplied by the total effective length of the entanglement to determine the total weight of the required materials. Divide the total weight by the vehicle capacity to determine the number of trucks or truckloads required to haul the material. Footnote b, to table 4-2 states the vehicle capacity should be 2268 kgs, which equates to 2 l/2 tons. Use of this weight limit will enable you to make an accurate estimate of the number of trucks required, whether 2 l/2 ton cargo or 5 ton dump trucks are used. The 5-ton dump has less than l/3 the volume capacity of the 2 l/2-ton cargo truck, and the bulk or volume of wire entanglement materials will limit a 5-ton dump truckload to approximately 2 l/2 tons.
Lesson 4 Practice Exercise
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