vation.

At night, lookouts are usually posted at listening points located in
or beyond the line of obstacles. These will be discussed under
obstacles.

=1159. Supporting Points.= In some cases small supporting points may
have to be established close behind the general line of trenches for
the purpose of breaking up a successful attack on the trenches and to
aid in delivering a counter attack. These points are strongly
entrenched and have all around wire entanglements and are garrisoned
by from 20 to 40 picked men or by larger forces if the situation
demand it. In some cases machine guns are added to the force in the
supporting point.

=1160. Example of trench system.= Having discussed trenches and
obstacles somewhat in detail, let us take a combination of the whole
showing a complete system such as is used today. (Fig. 40) is a good
example.

[Illustration: Fig. 40

FIRST LINE FIRING TRENCH]

Beginning at the front we have the line of wire entanglements or
obstacles with their listening posts X, for guarding them. Connecting
the listening posts to the fire trenches are the communicating
trenches. The fire trenches are shown by the heavy black line running
about 60 feet in rear of the obstacles. Note the many traverses shown
by the indentations in the line. Points marked M with arrows
projecting to the flanks are machine guns, so located as to sweep the
front of the position with a cross fire. Points marked S are
underground shelters for from 3 to 6 men. Points marked S' are
shelters for 30 men. In rear of the firing trenches at a distance
varying from 100 to 200 feet is the line of cover trenches. This line
is connected with the fire trenches by the zig zagged line of
communicating trenches. Note that the latrines (L) and first aid
stations (F) are just off from the communicating trenches, while the
larger shelter for men (S') are near the cover trenches. As the note
on the diagram shows, the trench requires 250 men to occupy it with
double that number in support. The trench has 108 loopholes with
spaces between provided with a higher banquette so that the whole
parapet may be manned for firing.

On the battlefields of Europe today there are generally three lines of
fire trenches. This permits the defender to fall back to a 2nd or 3rd
prepared position in case he is driven out of his first trench. On a
hill we find a fire trench near the foot of the slope, one just
forward of the military crest, and the thir