3.  DEFENSIVE.—­It is here that the flanking fire is especially necessary.  In the defensive preparation of a position the machine guns must be so placed that they will provide along the front several successive fire barriers.  The machine guns must be ready at all times to stop by instantaneous fire all hostile attack.  In order to have machine gun protection at all, it is absolutely necessary that they be protected from bombardment.  This is best done by the following:  Place the machine guns under solid cover; make their emplacement invisible; echelon the machine guns in depth.  The cover must be placed where it can be hidden from the sight of the enemy, such as a counter slope, a position where it is impossible to blend it, relief with an accentuated slope of the ground, woods, brush, etc.  It is essential that the principal parts of the machine gun casemate be prepared in the rear.  Only in this manner will the work be done solidly and rapidly.  While the machine gunners and helpers do the excavating, specialists in rear prepare the parts for assembling.  The latter are then transported to the position and, the casemate is established, hiding the work with the greatest care from enemy observation.  Remember that it is of the utmost importance that the machine gun be invisible, so the firing emplacements must be made outside of the shelter, but near enough for the gun to be brought out instantly and put into action.  All communicating trenches leading to the firing emplacement must be concealed.  Enough emplacements should be built to avoid firing daily from the emplacements especially reserved for cases of attack.  Do not place too many machine guns in the first line; in case of a violent bombardment they are sure to be destroyed.  The object to be attained is to install the machine guns in conditions such that if the enemy penetrates our first line, by aid of his bombardment or asphyxiating gas, his infantry, as it advances, comes under the fire of machine guns echeloned previously in depth, under whose fire it must stop.  It is not a matter of sweeping a wide sector, but of giving over certain strips of ground flanking fire which will cut down surely the enemy’s waves when they push forward.  The commander should, therefore, divide between the first line and the terrain in rear, the machine guns which he controls, organizing for each particular case a firing emplacement in accord with the surrounding ground and the purpose in view.

GENERAL RULES FOR INSTALLATION.

Machine gunners must under no circumstances abandon their positions.  They must, when necessary, allow themselves to be surrounded and defend themselves in their place to the end.  In many cases the heroism and tenacity of a few machine gunners have permitted the rapid retaking of a lost position.  To provide for this resistance to a finish, the machine gun emplacements must fulfil the following conditions: