When siting communication trenches, two considerations come into conflict with one another; the desire for protection, and the necessity of rapid and easy transit. It is obvious that a C.T. is of vital importance to the firing line in the getting up of supporting troops, ammunition and stores rapidly and without undue fatigue. It is also obvious that it must give as much protection as possible to the troops using the C.T., but it must be recognized that the protection given must not interfere with rapid transit by making the C.T. too narrow. It must also be kept in mind that rapid transit in itself gives a certain amount of protection for the simple reason that the easier and quicker the transit, the less time are troops delayed in the C.T.’s in which protection is required, and if troops can cover the danger area in 10 minutes, they are plainly in danger for a less period than if it took 30 minutes to struggle over that same area. This rapid transit, only obtained by a dangerously wide communication trench from support or reserve lines and from dugouts, also makes it possible for less troops to be regularly on duty in the fire-trenches, which are always uncomfortable and dangerous, especially during a bombardment, and it also enables supports and reserves to be rushed up quickly when the occasion demands.

It can be plainly seen now that a compromise must be effected between claims of protection and rapid transit, so that the size and shape of the C.T.’s will vary according to their distance from a danger area. Generally speaking, the nearer to danger, the more must the claims of rapid transit give way to those of protection.

Disregarding for the time being the claims of protection and only considering rapid transit, there are these things to be considered: First, that a C.T. be as short as possible, making use of contours, sunken roads and other natural features to avoid digging as much as possible. Second, that a C.T. be as straight as possible, which not only shortens the distance but avoids turns and corners which interfere with speed and which require renewed effort at every turn. These sharp corners and turns must always be avoided. This can be done without weakening a trench or increasing the risk, and every effort should be made to save troops carrying full equipment, stores, ammunition, or rations from unnecessary tiring, hindrances, and difficulties, such as sharp corners and turns. Third, the C.T.J.’s must be as level as possible, as they are generally slippery, and inclines or declines should be avoided as they very often cause accidents. A longer C.T. following around natural contours is frequently more advantageous for this reason than a straight one over a hill, which it is only possible to make level by an amount of digging out of proportion to the result gained. The C.T. must be wide enough for requirements. These differ according (a) to the proximity of C.T. to the fire-trenches, (b) to the number of C.T.’s available, and (c) to the use for which a C.T. is required, i. e., whether a double C.T. (for both up and down traffic) or a single C.T. (for traffic in one direction only).

When a C.T. is close to the fire-trench, troops moving into it are practically themselves in the fire-trench and as each group has probably to get to a different part of that fire-trench, all necessary traffic up and down the fire-trench and disturbance of the men occupying it must be avoided. Rapid transit can advantageously be obtained by other means than the width of the C.T.; by dividing the single C.T. at some point from 30 to 60 yards in rear of the actual fire-trench into a number of small narrow C. T.’s, each leading to a group of 3 to 6 fire-bays, and these may again be divided into those for up and those for down traffic.

This system requires a fair amount of thinking out and all the trenches should be plainly marked and named. These names are placed on notice boards at the different junctions having the proper indications and rules directing the use of up and down traffic. This is and should be rigidly enforced during both quiet and active periods, but takes on a much greater importance during active periods.

The width of these single C.T.’s running close to the fire-trenches should be enough to allow a man carrying full equipment, stores, or rations to pass along easily and without bumping the sides with his equipment or burden; approximately two feet at the bottom with ample room at all corners. The width of a single C.T. for down traffic only should be wide enough to allow for passage of a laden stretcher, especially at the corners, as a stretcher is a very clumsy thing to get around these corners and often the delay caused has very serious consequences.

As a C.T. leaving a fire-trench gets farther away, the width should be as soon as possible such as will allow two men to pass one another fully equipped without jostling or scraping the sides of the trench, or approximately 4 ft. at the bottom. This width with recesses described later allows rapid transit for troops passing each other in quiet parties and allowing a much greater safety in an emergency when there is no down traffic.

The front is always referred to as “up.”

Another advantage to be gained in the width of the C.T. is in the fact that it is much easier to keep dry and usable. It permits laying of regulation floor boards, allowing enough room on each side of them for the purpose of drainage, and is a means of preventing falling soil from covering the floor boards. Water will not drain off or through soil which is continually trampled on and has become sodden or irregular, and unless the floor boards are kept free from soil, they soon become useless, crooked and immovable. The width of these trenches allows the wind and sun to reach the bottom of the trench, thus helping a great deal in keeping it dry. There is no such thing as a communication trench 18 inches wide at the bottom and 24 inches wide at the top; diggings of these dimensions are nothing more than drains which in an emergency only are struggled through when passing in the open is still more impossible, and they should not be given any consideration whatever as a C.T.

The features required in a communication trench, regardless of the claims of rapid transit and only considering protection, are:

(First) Frequent traverses or turnings to avoid the effect of enfilade fire, to localize the effect of a bursting shell or bomb, to make difficult a hostile advance down the C.T. and to enable bomb parties to resist more easily their advance.

(Second) A trench that is sufficiently narrow will localize the effect of a bursting shell or bomb and minimize the effectiveness of hostile fire, which must have a high degree of accuracy to be effective. But the quicker over the ground the shorter the period of danger, and shell fire of any degree of accuracy will substantially narrow one of these narrower trenches, damaging the walls and causing casualties and other obstructions which will render passage impossible with either one or two results. Delay caused at a critical moment, or the occupants trying to obtain a passage up the trench in order to take any part in the fighting, would have to come out into the open sooner than necessary. The shelling of the C.T.’s usually is heavier for perfectly obvious reasons during an attack and when rapid transit through them is of the utmost importance. A narrow trench generally takes as long to dig as one of the wider type, owing to the restricted area in which to work.

(Third) If invisibility be possible, it is an excellent feature, but in nine hundred and ninety-nine cases out of a thousand it is hardly possible. An observed C.T. indicates the position and direction of supports, stores, reserves, dugouts, etc. This fault can be corrected to a certain extent by the careful use of the contours, dead ground, sunken roads, and all natural features, such as woods and hedges. Artificial cover may and does assist concealment, but sooner or later hostile aerial observation and photographs disclose the position of more easily concealed things than an excavated C.T. It is frequently the shadow at the bottom of a trench which gives its position away to aircraft, and the narrower the trench, the more prominent is the shadow. The soil, which is generally a different color from the surface soil, must be thrown up on either side as time does not allow it being carried away. Unless in a place of artificial cover through the length of the C.T., it is usually necessary to admit the impossibility of concealment and utilize time more profitably by taking protective measures.

Rapid transit to a fire-trench is of greater importance than rapid transit from a fire-trench, and the importance of protection is greater as the fire-trench and its dangers are approached. Methods of construction should be based on this idea and the arguments given above.