French Wire-Entanglement and Obstacle Construction
The following is taken from Trench Fortifications, 1914-1918: A Reference Manual, French Trench Warfare, 1917-1918: A Reference Manual, and the 1916 and 1918 editions of the Manuel du Chef de Section d'Infanterie ("The Manual of the Infantry Section Leader").
The principal accessory defenses on the Western Front were wire-entanglements, followed to a lesser extent by abatis. However, anything and everything that could impede the enemy, holding him under the fire of the defender, was utilized as an obstacle. Wire-entanglements are normally formed from several rows of stakes joined together by a network of wire, primary
Placement of Wire-Entanglements and Accessory Defenses
Wire-entanglements and accessory defenses should be placed at a distance from the trenches which permits easy observation, while at the same time keeping the trench outside the zone of accurate artillery fire directed at the accessory defenses. A distance of about 30-50 meters (100-165 feet) generally satisfies these conditions. Moreover, this distance is variable, for the accessory defenses are not necessary parallel to the trenches which they protect. Rather, they should be traced completely independent of the trace of the firing line so as to confuse the enemy's range finding. Trace all necessary salients so that flank fire will sweep the exterior edge of the defenses. Any defenses should be entirely swept by fire from the first line trenches. Otherwise the enemy can come and destroy them without danger.
Wire-entanglements and accessory defenses should be placed 30-50 meters (100-165 feet) in front of the trenches so that artillery fire or flame-throwers directed against the trench would not strike them. Any defenses should be entirely swept by fire from the first line trenches. Otherwise the enemy can come and destroy them without danger. They should be traced completely independent of the trace of the firing line so as to confuse the enemy's range finding. Trace all necessary salients so that flanking fire will sweep the exterior edge of the defenses. They should be hidden from both ground and aerial observation. If possible, they should be concealed behind a natural or an artificial embankment giving protection from the enemy's artillery fire. Alternately, they can be placed in pre-excavated inundation a meter in depth. Additionally, the vegetation within the entanglement as much as possible should be preserved.
Preferably, an entanglement should consist of several belts 10-15 meters (33-50 feet) deep, separated by a gap of 5-10 meters (16-33 feet), rather than a single belt 20-30 meters deep. The most distant entanglement is to be constructed first. The depth of entanglements should be greater in front of the passive zones of the line than in front of the active ones. Meanwhile, gaps for the coming and going of patrols and fatigue parties should be provided at various points in the entanglements. Such passages are set up in zigzags through the entanglements with movable obstacles left close by to close off them off.
Wire-entanglements and accessory defenses should be closely watched at night from advanced listening-posts placed near by, either just behind or in front of them. These can also aid in repelling enemy fatigue parties. The men assigned to these posts are to sound the alarm by means of signals, bells, shots, etc. Additionally for this purpose, noise-making devices should be attached to the entanglements. These can be simple tin cans or metal scrap. Before an offensive, obstacles are to be removed to give passage to the assaulting waves.
Construction of Wire-Entanglements and Obstacles
Wire-entanglements can be classified in the following categories:
The standard entanglement consists setting up rows of 2' 10" or 5' 4" in length or wooden stakes 5' to 6' 8" in length and 3-4" in diameter. Two rows of stakes made one strip, which were interconnected with a network of wire, preferably barbed, and could be infinitely expanded upon. Each strip comprised three panels:
Note: if wire was lacking, the zigzag panel could be foregone.
Every panel is constituted of 4 categories of wire:
To set up the standard entanglement four steps must be followed, which required ideally 37-40 men to construct.
- Tracing: A NCO or guide knowing the direction the entanglements must take, slowly walks toward the desired point of direction and traces the position of each row. He is followed by a pair of stake setters on each side (4 in total) and 2 paces apart, walking in a parallel direction. At every other pace, these men lightly pound down the stakes brought up by the supply men who carry them.
- Driving: The stake setters are followed by two drivers carrying wooden mauls (some leather cushions to soften the noise) and two helpers who hold the stakes straight and place a sack on top to deaden the noise.
- Wiring: A total of 24 wire men were divided into crews of two men, with 4 crews assigned to each panel of wire. For each panel, one crew handled the lower wire, 1 crew for the top wire and 2 crews for the diagonal wire. For the first panel:
- Supplying: The number of men needed to supply the stake men with stakes depends upon the distance the material has to be transported. One man can carry 3-5 stakes according to their thickness. Eight men are needed then (2 per panel) to supply the group.
The second and third panels are accomplished in the same manner. The wire itself is not cut until the end of the entanglement is reached; the entanglement is one, continuous strand.--The first crew attaches its wire to the lower part of the first stake, winds it around the lower part of the second stake, and so on.
-- The second crew attaches its wire to the lower part of the first stake, winds it once around the top of the second stake, then down again to the bottom of the third stake, and so on.
--The third crew does the same but starts at the top of the first stake.
--The fourth crew attaches the wire at the upper part of the first stake, winds it around the top of the second, and so on.
Note: whenever possible, chicken wire or metallic trellis should be fastened to the furthest row of stakes toward the enemy in such a manner as to prevent the introduction of a long charge of explosive into the entanglement.
Another version of standard entanglement using wooden stakes (and requiring fewer men to construct) consisted in arranging the stakes into a rectangle, with one stake on each corner and a fifth stake in the center. The long-sides of the rectangle were roughly 8 feet in length. All the stakes were then interconnected by a network of iron wire, preferably barbed wire. Seven rows of stakes produced an entanglement roughly 43 feet in width. To construct this entanglement, two men are assigned to drive stakes. The positions for the stakes are marked using a triangle of cord. The stakes are then hammered down with a wooden maul and driven in to irregular depths, so that the stake heads are alternately 2' 8" to 4' high. Two men are detailed to carry the wire spool and unwind it, making a turn around each stake, as another two men fasten the wire to the stakes.
This could be added upon invariably to produce an entanglement of a great depth.
Normally, the wire was brought up on spools or coils by means of a staff or pole passed through the center, carried by two men. However, it could also be brought up in shorter, lighter lengths by wrapping the wire around in a figure-8 fashion around a stick. The stakes were transported in the arms of the men.
In the immediate presence of the enemy, to avoid attracting attention by the noise of driving stakes, special iron stakes were used with cork-screw bottoms which were screwed into place. One type was a T-shaped stake (5' 5" high), which came with a special key allowing for it to be screwed in place (to a depth of 2' 4"). This stake was furnished with holes and notches for the passage of wire. More preferable, however, was the round stake which had three loops worked into its length (giving it the nickname of the "pig-tail" stake). In this case, the wire was fastened through and around the loops. These came in two lengths: one 5' 4" high and the other 2' 10" high (specifically for stringing low wire entanglements). These were screwed down 1' 4" and 1' 2", respectively.
In the case of both the T-shaped and pig-tail stakes, the entanglement is arranged in the manner described above with the exception of the wiring. As holes/notches and loops are already provided, three parallel lines of wire are strung (high, middle, low) for each panel, foregoing the diagonal lines.
If under urgent circumstances the entanglement needed to be set up quickly, pre-prepared wooden stakes (3-4" in diameter) with 3 loops of wire fastened to the top (to attach the interconnecting wire to once in place) could be used. These were hammered into place, and the interconnecting wire attached to the loops to make the three panels of the rows. Alternately, right-angled iron stakes (5' 4" high) can be used which are furnished with holes and notches for the wire to pass through. The stakes are hammered down to a depth of 1' 8". In the case of the angled iron type, a spade is placed on the top of the stake and it is pressed into the earth.
Entanglements comprised of these types of stakes are set up somewhat differently to better facilitate speed (in theory, a dozen men could build a belt almost 75 feet long and 33 feet deep in less than two hours). The stakes are arranged in sets of 5, which take on a rectangular shape by making two equilateral triangles that are joined at the vertex (or, in other words, at the stake placed in the center of the rectangle). Moving parallel to the front, the stakes are placed 6' 8" from each other. Moving perpendicularly to the front, the stakes are placed 5' 7" from each other.
For each panel, the wire is strung in the same pattern as the standard entanglement using wooden stakes, with the order progressing in the order shown below.
Note: the entanglement is anchored in front and in rear by flanking stakes which help to maintain the entanglement.
An entanglement level with the surface of the ground constitutes an accessory defense which may be very effective when it is well concealed and thus takes the enemy by surprise. There were any number of variations on this type of entanglement. The most rudimentary was to simply drive sharpened wooden stakes, about 2 1/2" in diameter, into the ground at an angle so that the ends projected no more than 1 foot. Vegetation renders these entanglements invisible even at a very short distance. Other types of ground-level obstacles consisted primarily in utilizing iron wire loops (non-barbed) to trip up and slow down the enemy.
The 'double lace' is nothing but the same kind of trap used by poachers, consisting of a length of wire (about 2 feet long), the ends of which are looped and tied back to the wire. The wire itself is fastened to a short stakes with a staple or bent nail, which in turn is driven straight into the earth to the depth of about a foot. The 'simple lace' is a clove hitch made with a length of wire, the ends of which are attached to two forked pickets driven into the earth. The loops, placed between the pickets and bound at the top using a short piece of wire, stand about 6" vertically off the ground. Another type of ground-level entanglement used when time or material is limited is can be made simply by unwinding and stretching out wire on the ground. The wire does not have to be laid out perfectly and it is advisable to leave numerous loops scattered on the ground, which are secured to the ground using small pickets.
The Brun entanglement consists of the juxtaposition of a certain number of hollow cylinders or coils, the surface of which is formed by an entanglement of large mesh of either barbed or smooth wire. Each coil weighed 17.5 lbs, was 4' 6" in diameter, and could be stretched out to 30 meters (100 feet) in length. This entanglement is very rapidly put in place and is used especially in the organization of a recently conquered position, being used to create an obstacle in the shortest time possible to hinder enemy counter-attack, or to obstruct a passage or breach. It was forbidden to use the Brun entanglement in front of the second or support line trenches. If properly fastened in place, the Brun entanglement retains the same resistance as a standard entanglement.
To set up a Brun entanglement, five men are required. Two men hold the ends of the coil, one on each end, and extend the entanglement out to its full length or the length desired. Meanwhile, another two men disentangle the turns and jerk the coil about in order to regulate the stretch. Left alone, the coil, when subject to any shock, shortens until it is no more than 20 meters (67 feet) long and 1 meter (3' 4") in diameter. Thus, the fifth man fastens the coil to the ground (and binds it to those already placed, if such is the case) at 4 or 5 points using staples, small wooden forks or (in hard ground) iron hooks.
The coils are laid out in parallel lines (and parallel to the front), starting with the furthest coil first and taking care to alternate joints.
In certain cases, it may be useful to stack the coils into two tiers, fastening them to trees and posts, or lacking these, arranging them in a pyramid fashion.
METALLIC TRELLIS ENTANGLEMENT
Metallic trellis entanglements are comprised of strips of trelliswork 26 meters (84 feet) long, constructed at the rear with thin wooden pickets or stakes (5' 4" high). The pickets are placed at regular intervals, 7' 8" from each other, with smooth or barbed wire arranged in between. The strips are then rolled up for transport, each roll weighing 83.5 lbs. It is carried by two men by means of a staff passed through the center of the roll.
To set up the trellis entanglement, the roll is brought up and unrolled on the ground by two men. Another pair of men fix it vertically in the ground. Other types of rolls, twice as long, are set up solely in the rear. These are unrolled in zigzag lines. An infinite number of lines can be added to both the length and width of such an entanglement, with care being taken to fasten the abutting pickets together.
When not all the trellis entanglement is used and there is left over trelliswork available, several lines of improvised entanglements can be constructed. These are about 2' 4" high and composed of pickets or stakes 1-4" in diameter, spaced about 5-6.5 feet apart and joined to an existing network of barbed wire. Whenever possible, intermediate pickets are placed in the intervals and are joined to the outer pickets by barbed wire, thus increasing the cohesion of the entanglement.
Commercially made trelliswork used to enclose private property can be employed advantageously in particular cases. For instance, in woods the wire can be fastened to trees.
CHEVAUX DE FRISE OBSTACLE
Chevaux de Frise (sing. Cheval de Frise) was the general name used to described a number of mobile, free-standing obstacles which were employed individually as obstacles or as large, networked entanglements. In essence, they consist of a wooden or metal frame which often had wire then stretched around it. Specifically, they can be used to obstruct passages left open in the defenders entanglement, to repair breaches made by the enemy in the accessory defences, or to block roads or trenches (as 'trench blocks'). Moreover, they take the place of barbed wire entanglements when the soil is particularly hard or if the enemy is in close proximity; in both cases the driving of stakes can not be accomplished. In the latter instance, the chevaux de frise are thrown pell-mell in front of the defensive works and, when circumstances are favorable, are gradually secured to the ground. And because the chevaux de frise could be constructed at the front (in the trenches) or in the rear (and then carried up), they were particularly convenient.
There are numerous types in use. One is the chevalet, or "trestle." In the English language, this goes either by the name of the "Spanish Rider" or the "knife rest." It consists of two (St. Andrew's) crosses made of planks or poles nailed or wired together and joined by a pole 3 meters (10 feet) long and 4" in diameter. The pole itself held by nailing the crosses onto the ends, or by resting the pole on top of the crosses and securing it with smooth wire. The whole obstacle, which is 4 feet high, is bound by barbed wire along the sides and diagonals. The trestle could be reinforced by attaching an adjoining plank or "tendeur" to the ends, which also facilitated easier handling. Besides being utilized in the construction of entanglements, the trestle was particularly well adapted for acting as a moveable trench block. It can be placed on the parapet and, in case of enemy intrusion, is easily and rapidly pulled down into place.
A more antiquated form of the trestle consists of a series of poles, stakes or logs (the ends of which were sharpened), or pointed metal stakes, which are again fastened together in a cross-shape with a pole or bar joining them. This type was without wire of any kind and was not as common.
Another second type of cheval de frise was comprised of a frame of poles or logs (3-4" in diameter) joined together to form a rectangular cube. Four of the poles/logs formed the vertical supports with the others horizontal on the sides and ends, all of them fastened together by means of smooth wire. The whole obstacle was then bound in barbed wire. It measured 12 feet long, 8' 8" wide and 5' 4" high. As this type of entanglement was inherently larger and heavier it was more likely reserved for support line areas, such as acting as a road-block or a barrier to a prepared location.
In both cases (trestle or cube obstacle), a formidable entanglement can be created by arranging a certain number of obstacles in rows or in alternating zigzag patterns. By fastening them to the ground and joining them together with wire, a large network may be formed which can be infinitely expanded upon. Whenever possible, pickets can then be placed at intervals between the joining wire. In the case of the soil being particularly hard and not suitable for planting stakes, this presented a real alternative to the standard entanglement. Moreover, if a section was damaged or destroyed, it can be easily replaced by installing another as need be.
A different type of cheval de frise which was smaller and more manageable was the hérisson, or "hedgehog" (as it is also known in English). This consists of 3 triangles formed from logs, poles or angled iron bars (4 feet in length), each perpendicular to the planes of the other two. The ends are all bound together with wire. Like the trestle, the hedgehog was particularly well adapted for acting as a moveable trench block. It can be placed on the parapet and, in case of enemy intrusion, is easily and rapidly pulled down into place.
Cylindrical obstacles are composed of sections of Brun entanglements fastened to 4 (St. Andrew's) crosses made of angled iron bars. They are secured in the centers by smooth wire wrapped about a pole notched to receive the blades of the iron bars.
Protection against grenades can be had by placing above the fire-ledge a vertical panel of wire-mesh (e.g. chicken-wire), which covers over the trench with a roof comprised of two panels of wire-mesh or of joined logs and covering over this roof with a light layer of earth. The example given in the figure below (a pivoting cage in chicken-wire) is very effective and has the added advantage of being able to be utilized instantly as a trench block in the communication trenches.