Artificial cover may be either excavated or built up, or a combination of both. Excavated cover will usually take the form of a pit of sufficient size to hold the tripod, ammunition, and three men, and deep enough to conceal the gun and men not only from view, but from fire at “effective” range. This form of cover is particularly good on a level plain, the muzzle of the gun being just above the surface of the ground. The rear side of the pit may require to be enlarged to take the long leg of the tripod where time is limited and the pit has not been made large enough to take the tripod in any position, but it is advisable to make the pit of sufficient area to allow the gun to be worked in any direction. With an adjustable tripod, the pit should be so deep that the gun is completely concealed below the surface of the ground, and it is only raised when it is intended to open fire. Other forms of cover consist of epaulements, trenches, sangars, etc., which will not differ essentially from those given in the manual of Military Engineering. In all types of “cover from fire” care must be taken that the cover is high enough to protect No. 1 from bullets fired at ranges up to 1,400 yards, taking into consideration the angle of descent of the bullets at that range and the distance of No. 1 from the cover. Cover can seldom, if ever, combine all the points enumerated here, and it will lie with the section commander to discriminate between them and decide what points he will sacrifice in favour of others more important: thus it may be necessary, where concealment is the chief object, to forgo “cover from fire” at the longer ranges in favour of a low parapet or even none at all. It is only possible to indicate in outline the principles that should be followed; practice in training and the experience thus gained alone will make the reader an expert. Shields will be found of great value in the final stages of the battle, when machine guns are pushed up to close range to assist in the final assault. They are too heavy to carry on the guns, and should be with the ammunition in the first-line transport, where they are easily obtained if required. COVERING FIRE Machine guns will often be used to cover the advance of infantry from “long” to “effective” range when the artillery is still occupied in the artillery duel and the infantry first come under effective rifle fire from the enemy. The ease with which they can instantly open and cease fire, concentrate on a particular spot, or sweep a line of trenches, renders them particularly suited for this purpose, and the Japanese constantly used them to keep down the enemy’s rifle fire in this manner during the late war.