In determining the area of overhead cover to be provided, allow 6 sq. ft. per man for occupancy while on duty only, or 12 sq. ft. per man for continuous occupancy not of long duration. For long occupation 18 to 20 sq. ft. per man should be provided.
It is not practicable to give complete cover to rifle positions that will successfully withstand the heavy artillery of today. The use of overhead cover is usually limited to that sufficient for protection against rifle fire, machine gun fire, and shrapnel.
[1155]. Cover trenches are constructed to provide safe cover for the supports or reinforcements of the fire trenches or to provide cooking and resting facilities for the garrison of the neighboring fire trenches. The important point in cover trenches is safety. They vary in design from the simple rectangular trenches to elaborately constructed trenches having overhead cover, kitchens, shelters, latrines, dressing stations, etc. Cover trenches must not be mistaken for a secondary position, they are cover for the firing line, supports and reserves until they are required in the fire trenches. The cover trench requires a depth of at least 6 feet to protect men standing. Greater depths may be used when necessary. [Fig. 36] is a section of an open cover trench and [Fig. 37] of a closed one. This section may be used for a communicating trench. [Fig. 38] shows a cover trench close to a fire trench. The character of overhead cover for trenches is shown in the diagrams under overhead cover. The distance of the cover trenches varies with the situation. The experience of the European war places the cover trenches from 15 to 50 yards in rear of the fire trenches. These trenches furnish shelter for at least 2/3 of the firing line and supports.
Fig. 36
| Fig. 37 | Fig. 38 |
The reserves are furnished yet more elaborate shelter, with plenty of room for the men to lie down and rest and when practicable, bathing facilities are provided.
[1156]. Dugouts. An elaborate system of dugouts has developed along the lines occupied by the troops in the European war. These dugouts are located from 14 to 40 feet below the ground and are reached by stairs in timbered passage ways. At the foot of the stairs a tunnel or corridor runs forward and on either side or at the end, rooms have been dug out varying in size. Most of these rooms have been timbered and lined. Many are electrically lighted. In some of these underground shelters, accommodations for several hundred men have been prepared with all of the necessary facilities for making them comfortable. It must be understood that such elaborate preparations can only be made when troops face each other in trenches where operations have developed into practically a siege.
[1157]. Communicating trenches. These trenches as the name implies are for the purpose of providing safe communication between the cover and fire trenches. They may be also constructed just in rear of a series of fire trenches to provide a means of communication from one to the other. Communicating trenches also extend to the rear of the cover trenches and provide safe passage to fresh troops or supplies. These trenches are usually laid out in zig zag or curved lines ([Fig. 39]), to prevent enfilade fire from sweeping them. As a general rule excavated earth is placed on both sides of the trench to afford protection, the depth is usually from 6 to 7 feet. ([Fig. 15]) shows a typical communicating trench.