The machine guns allotted to the flanks should form the supports to the cavalry there; and if two batteries are available on each flank, one should accompany the cavalry to enable it to remain mounted, while they provide the fire action necessary to support it in the attack and to cover its retirement in the face of superior numbers. The detail of such action has already been given with the Independent Cavalry. The other batteries will break up into sections and move parallel to the line of retreat in single file at wide intervals, keeping touch with the cavalry by scouts on the outer flank. The object of this battery is to seize and hold good positions on the flank of the line of retreat until the main body has passed. The scouts of the rear section of this battery should get into touch with the scouts of the flank gun of the centre battery from time to time, to ensure proper co-operation between the various batteries. The importance of concealed positions from which to ambush the pursuers must not blind machine-gun commanders to the necessity for seizing and holding to the last possible moment, even at the risk of capture, every position from which the retreat can be effectually covered and the pursuit delayed. Should a river or other natural obstacle be encountered on the line of retreat, machine guns must freely sacrifice themselves in covering the retirement of the cavalry across the bridge or beyond the obstacle. Cavalry is the most costly of all arms, and cannot be replaced during a campaign; machine guns are the least expensive in proportion to their fire value, and the easiest to renew; they must consequently save the cavalry when they can, even if they sacrifice themselves in doing so. ESCORT TO ARTILLERY There is one important duty which machine guns are able to perform better than any other arm, and that is escorting artillery, but more especially horse artillery. When cavalry are detailed for this purpose they not only deprive squadrons of much-needed men, but can only provide three rifles in action to every four men of the escort, owing to the necessity of providing horse-holders. In addition to this drawback, the horses provide a costly fire-trap for the shells of the enemy’s guns which may go wide of the battery. For these reasons, where it is possible to spare them, a section of machine guns should be allotted to each battery of artillery when an escort is necessary.