fire on the backs of the troops.

=565. Use in villages.= In villages, machine guns were used with
terrible effect, firing from cellars or windows. The only successful
method of destroying them was with hand grenades and even this was
costly.

=566. Location on the defense.= On the _defense_ machine guns should
be mounted in salients and at points where cross fire can be obtained.
This makes it more difficult for the enemy to locate the guns. Frontal
fire is not so often successful.

=567. Location in attack.= In the _attack_ it is accepted that machine
guns must cover the Infantry at short and long ranges while other
machine guns must accompany the attacking troops to hold the positions
or trenches gained.

The second or third line would seem to be the best position for
machine guns when accompanying troops.

[Illustration: Machine Gun Emplacement: Section aa]

[Illustration: Machine Gun Emplacement: Plan with Cover Removed]

=568. Economy of men.= Owing to its rapid and effective fire, and the
comparative ease with which it can be concealed, the machine gun
permits a great economy of men on a front and the concentrating of the
forces thus freed for use in other parts of the field. This was done
on a large scale on the Russian front by the Germans in 1915. They
constructed miles of wire entanglements in front of positions occupied
with an enormous number of machine guns and comparatively few men. The
main forces were thus free to be transported wherever danger
threatened. In this manner the Germans replaced men by machine guns
and wire and were able to cope successfully with the immense Russian
Armies. The above plate shows a typical machine gun emplacement,
constructed in the field. Many elaborate emplacements have been
constructed in the European war, using steel and concrete, but for a
hasty cover in the field the simple emplacement shown in the figure is
recommended.

(NOTE.--For a more detailed study of machine guns, see Subject XI,
Machine Guns in Action, School of Musketry, Fort Sill, Oklahoma,
and Combined Cavalry and Infantry Drill Regulations for Automatic
Machine Rifle, cal. 30, 1909, War Department, 1915.)

AMMUNITION SUPPLY

=569. Method of supplying ammunition to combat train.= The method of
supply of ammunition to the combat trains is explained in Field
Service Regulations. (547)

=570. Combat train and the major's responsibility for its proper use;
a rendezvous for each