LOOKOUT AND LISTENING POSTS
Except when the garrison are actually required to man the parapet, they
will be kept under cover, with the exception of a few lookouts, whose
duty it is to give timely warning of the movements of the enemy.
When the opposing forces are in close proximity to each other mining
operations are generally resorted to by both sides to compass the
destruction of the opposing works and open the way for an attack.
Lookout and listening posts serve the double purpose of having a few
men at the most advantageous places for observation at the front and
flanks and providing points at some distance to the front of the first
line fire trenches from which listeners may be able to discover the
location and direction of enemy mining operations before they really
menace the fire trench.
In the normal case there will be some natural cover available. Such,
however, is not always the case, and specially constructed observation
stations have to be provided.
The posts should be placed in advance of the first line trench, the
distance depending upon circumstances which have to be determined in
each particular instance. They must be fully protected from reverse
fire so that there will be no chance of the observer masking the fire
of his comrades manning the fire trench.
Unless the ground is very favorable it will be found difficult to
provide for observation above ground. Where there are natural features
such as embankments, mounds, hedgerows, ruins of buildings, etc., it
may be possible to make provision for observation even by day.
Where a loophole is used, the type having the narrower end outward
should be provided.
In the open type of post the observation directly to the front may be
greatly facilitated by the use of the periscope. (Plate 11.)
A good, strong parapet thrown up and chopped off at the corners will
enable the observer to cover areas from an oblique direction from the
post and protect him from fire from the front.
In the covered type the observer is provided loopholes having the
splay towards him. These may also be constructed to the oblique rather
than to the front. When this is done, provision must be made to cover
the entire front of the position from the several posts. (Plate 12.)
The post may be connected with the first line fire trench by a narrow
zigzag trench or by an underground passage. If the former, it must be
thoroughly concealed and have no excavated earth visible. If it can be
located along a hedge or some other natural feature its location may
remain unknown to the enemy for a considerable length of time. Where
a communication gallery is constructed the roof and walls must be
suitably shored up by casing and supports.
The sentinel in the listening post carries no accouterments. It has
been found that the creaking noise made by equipment when the sentinel
moves has been taken for mining operations of the enemy by his comrades.
[Illustration: Plate 11.--Open type of listening post.]
[Illustration: Plate 12.--Covered type of listening post.]
Listening galleries should never be left without a sentinel. There
should be a depot of arms and hand grenades near the entrance to the
gallery in case men are attacked while on duty from either above or
below ground.
[Illustration: Plate 13.--A listening and observation post.]
Listening will be conducted at specified times, or on some prearranged
signal, and for a definite period. During this time all within the
listening area, including the trenches, must remain absolutely
motionless.
Infantry manning a trench can assist listening by digging a small pit,
6 feet deep below the trench, and running a bore-hole out 20 feet or
more.
The enemy is always listening for indications of the direction and
position of gallery heads. Work must therefore be carried on with a
minimum of noise. Shouting down the shafts of galleries is absolutely
forbidden.
When the mining operations of the enemy are detected a report should be
made at once to the officer in charge of that section of the trench.