It is the duty of supports to reinforce and extend the firing line, to cover the flanks (par. 222 German I. D. R.), to act as a reserve, and, in case of necessity, as a rallying force upon which the firing line can fall back. The presence of supports increases confidence in attack, and the power of resistance in defense. Supports enable a leader to influence the action, to give a firing line that has been checked the impetus necessary to carry it forward, and to affect the action by sending reinforcements to points where he wishes to gain an advantage. The support follows that part of the firing line which, in all probability, will need its assistance; if part of the same organization as the firing line, it follows in rear of the center, otherwise in rear of a wing. In a company advancing alone over covered terrain, it will sometimes be necessary to place small supports in rear of both flanks. Firing lines can perhaps advance for some time under hostile fire, whether they move by twos, by squads, or by platoons, but the power necessary for pushing home the attack must be imparted to them from the rear; otherwise the energy of the attack will spend itself. The necessity of having supports in rear of the firing line is clearly illustrated in the very instructive engagement at Wagon Hill in front of Ladysmith (6th January 1900). In this fight all attempts to push the firing line forward failed, and the necessary impetus for the decisive advance was not given until fresh supports were fed into the firing line.[100] [100] _The Times History of the War in South Africa_, III, p. 200. In hilly country the supports can fire over the heads of the skirmishers in front of them without neglecting their proper functions. (Switzerland and England). Such opportunities should not be overlooked, as they increase the volume of fire. Distances depend upon the object to be attained by the action and upon the terrain. When a decision is sought, distances should be decreased in the course of the action. When this is the case, the leaders of all grades should be animated by but one desire, that of being in front in order to participate in gaining the victory. The duration of the crisis of an action is usually brief, and in a very few rapidly passing moments the leader must decide what to do with the troops remaining available.