In _attacks_, supports are useful for filling up accidental gaps in the front line—for prolonging its flanks or covering them obliquely or perpendicularly—for strengthening the skirmishers at any moment that these may find their numbers unequal to important work before them—for relieving them when they or their ammunition become exhausted—for coming up in close order to charge bridges, streets, villages, or other defiles, too strongly occupied to be forced by the skirmishers, and to serve as bases, when time allows it, for the formation of squares against cavalry. In _defences_, in addition to the foregoing duties reversed as to bodies retiring, supports have the highly important responsibilities of leading the skirmishers in the true and best line of retreat—of opening that line in all suitable places for their convenient passage, and of taking care that it be not intercepted by the enemy. Reserves, particularly so called, supply the places of supports when necessary, and go to the front for any object requiring the intervention of a particularly strong, steady, and concentrated force. Without express orders, supports should not move forward to occupy accidental gaps in the extended line, except on ground so intricate, or under circumstances so emergent, that the skirmishers themselves cannot readily regain their lost communications. In most movements, set unvarying sentences of command promote alertness and prevent mistakes. For prolonging in the same direction the flanks of the extended line—for covering them perpendicularly or obliquely—for strengthening the skirmishers by mixing others with them, or for relieving them; the following set, concise orders to supports obviously present themselves:— NO. —— SUPPORT.: PROLONG THE —— FLANK. In the same direction as the general line understood. DO. —— DO.: COVER THE —— FLANK, _perpendicularly_; with moderate licence, according to the features of the ground, understood. DO. —— DO.: COVER OBLIQUELY THE —— FLANK. _An obliquity of one-eighth of the circle_, with the same licence, understood. DO. —— DO.: STRENGTHEN NO. ——. To prevent mistakes, the word “strengthen” to be repeated with sufficient distinctness by the officers and non-commissioned officers of the Support to which it is given, when they arrive near to the skirmishers or the skirmishers near to them. DO. —— DO.: RELIEVE NO. ——. The word “relieve” to be repeated in like manner, for the same reason.