Extraordinary means have been resorted to in hiding the guns until they are needed. In the German line, dugouts underground were constructed to conceal the machine guns and crews. Often they permitted the first line of the attack to pass over them and then appeared in rear and opened a deadly 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.)