T bays may be sited with due and careful consideration while facing the enemy in an existing trench system. Thus it gives you the advantage of being able to take into consideration all the requirements of the field of fire, control of isolated areas, and the obtaining of maximum results from enfilade fire. These T trenches may be dug out from the old system without undue exposure of your men and if distance between the lines permits, and it is entirely possible to construct a new and generally more favorable line of trenches within 100 to 200 yards of the enemy’s trenches. Intervening ground between these T bays must be completely controlled by entanglements and mobile machine guns, or automatic rifles, able to operate from different alternating recesses in the control trench. Fire platforms should be placed in recesses at intervals in the control trench from which covering fire can be given. Artillery fire, to damage a T trench, must be very accurate. In a traversed trench a shell destroys not only lateral communication, but the defenders as well, whereas with a T shape, both fire-bays and control trench have to be ranged and hit. The success of the enemy is entirely local when capturing one of these T-bays, and he may be shelled by your own artillery without any danger or risks to those defending their T-bays. Control trenches should be dug first and zigzagged with the longer stretches facing the enemy. This gives you another fire-trench as well as a communication trench, and is also ready for use at any time needed before the T-bay is completed. On the completion of the T-bay, the corners of the zigzagged trench must be rounded off to make it easier and quicker for the movement of troops and carrying of stretchers.
DUGOUTS
It is only under very exceptional circumstances that under-cutting a trench wall is allowed, and then the shelter should be cut in the rear wall only. These shelters must be carefully supervised and watched by the officer, as men are very often careless, with the result that the shelters are dug in a hurry and poorly. Then it rains, the shelter falls in, and the men are no more. It should be high enough for a man to sit up straight, and long enough for him to lie down in, and deep enough for two men to lie side by side. It should be raised at least a foot above the floor level in the trench to prevent water from the trench floor coming in. A shelter smaller than these dimensions is useless. It has a demoralizing effect, destroying all activity, mental and physical. These shelters can only be properly made by cutting into the rear trench wall the necessary depth and length and right to the top. Then, with any material which is convenient, such as corrugated iron, brushwood, old rubber sheets, revet the sides and back. A corrugated iron roof is supported on posts at a depth of about a foot to a foot and a half below the normal level of the ground. Then, when possible, cover this with rubber sheets. If not possible to procure rubber sheets, simply cover with dirt excavated from shelter, taking care that it does not rise higher than your parados.
Fire Trench, Showing Entrance to Shelter
The shelter is of use only in a narrow or deep trench. Note that the floor is above the bottom of the trench.
A fire-trench, however, is not a proper place for shelters, and they are generally better as a weather protection than a shell-proof shelter. Even this should not be favored too much, as it tends to cause obstruction, delay and inconvenience in the passing of troops. The real dugouts for the accommodation of men holding a line are generally behind the fire-trenches in an immediate support line, or as in the case of T-bays, in the control trench and communication trenches leading to and from them. These are large dugouts, having a depth of 30 and 40 feet, and in some cases capable of holding 100 to 250 men, generally having from 5 to 10 exits and entrances. Here the men stay during bombardments and are generally safe from any caliber shell which may light on top, unless a half dozen should light in the same particular spot.
This work is generally of a very skilled and technical kind. Plans, drawings and labor are supervised by the engineers, expert tunnelers being used in constructing work, although the infantry supplies working parties to dispose of the dirt, etc., resulting from these excavations and to carry the materials and tools needed and required in the construction.
The design and general scheme of a small dugout which can be made by the infantry under the supervision of an officer, without the aid of an engineer, are here given. The dugout should be approximately 6 feet from floor to roof and about 8 feet wide, with an approximate length of 12 feet, thus allowing men to lie down and yet leave room for passage through. The width depends upon the number you intend to have occupy it. Each man requires 18″. Depth to be dug below ground depends entirely to what extent you may raise the roof upon the ground without making an unduly exposed hump which will at once tell the enemy a dugout is there. The thickness of the roof should be approximately 6 feet, constructed with side posts, cross beams, corrugated iron, waterproof oilcloth, sandbags and soil. Sandbag revetments should be used in the strengthening of side posts. When possible, although hardly ever so, walls should be lined with waterproof oilcloth and entrances so placed that they get as much sun as possible.