Elements of Trench Warfare

by William H. Waldron

3. Holding the enemy under the effective fires of the defenders.

The conditions that obstacles should fulfil are as follows. They must—

1. Be close to the defender's position. As a rule on the western front they are not more than from 50 to 100 yards distant. If they are too close it may be possible to throw hand grenades from the far edge of them into the defender's trenches.

2. As far as practicable, be sheltered and screened from the enemy. Shell fire is the most effective method of destroying obstacles. If they are not concealed they may furnish aiming points for the enemy's fire against the first line fire trench by his being able to estimate its location with reference to the obstacle.

3. Afford no cover or screen to the enemy.

4. Be so placed that the enemy will come upon them as a surprise.

5. Be so constructed as to be difficult of removal under fire and impracticable to negotiate while still reasonably intact.

6. Be arranged so as not to interfere with a counter attack. The obstacles may have occasional gaps left in them which may be mined.

The different classes of obstacles are: Abatis, low wire entanglements, high wire entanglements, barricades, mines, fougasses, crows feet, military pits with wire entanglements, inundations, etc.