Prepare for the obstruction of the communicating trenches in case the enemy should capture the fire trench: Have piles of sand bags above the entrance of each trench ready to be dumped into it. Have chevaux de frise lined up on one parapet of the trench and all held up in such a way by a single wire that when the wire is cut they will fall into the trench. Mines can also be prepared to blow up the trench when invaded. The communicating trench between the fire trench and the listening post should be covered with barbed wire screens or be tunnelled.
THE WATCH FROM THE TRENCHES.
12.—Trench Warfare an outpost duty.
Trench warfare, the inevitable form of modern warfare, is a continuous series of outpost duty. Hence it is based wholly on eternal vigilance. The patrols correspond to the scouts; the listening posts to the sentinels; the firing trench to the outguards; the cover trench to the supports. The safety of the sector depends entirely on the vigilance of the advanced elements and the rapidity with which supports and the reserves can be summoned.
Watching is thus the fundamental duty in trench warfare.
The following points should be kept in mind:
AT ALL TIMES
13.—Number of men in the fire trench.