256. In an advance by rushes, leaders of troops in firing positions are responsible for the delivery of heavy fire to cover the advance of each rushing fraction. Troops are trained to change slightly the direction of fire so as not to endanger the flanks of advanced portions of the firing line. 257. In defense, when the target disappears behind cover, platoon leaders suspend fire, prepare their platoons to fire upon the point where it is expected to reappear, and greet its reappearance instantly with vigorous fire. SCHOOL OF THE BATTALION. 258. The battalion being purely a tactical unit, the major's duties are primarily those of an instructor in drill and tactics and of a tactical commander. He is responsible for the theoretical and practical training of the battalion. He supervises the training of the companies of the battalion with a view to insuring the thoroughness and uniformity of their instruction. In the instruction of the battalion as a whole, his efforts will be directed chiefly to the development of tactical efficiency, devoting only such time to the mechanism of drill and to the ceremonies as may be necessary in order to insure precision, smartness, and proper control. 259. The movements explained herein are on the basis of a battalion of four companies; they may be executed by a battalion of two or more companies, not exceeding six. 260. The companies are generally arranged from right to left according to the rank of the captains present at the formation. The arrangement of the companies may be varied by the major or higher commander. After the battalion is formed, no cognizance is taken of the relative order of the companies. 261. In whatever direction the battalion faces, the companies are designated numerically from right to left in line, and from head to rear in column, _first company_, _second company_, etc. The terms _right_ and _left_ apply to actual right and left as the line faces; if the about by squads be executed when in line, the right company becomes the left company and the right center becomes the left center company. The designation center company indicates the right center or the actual center company according as the number of companies is even or odd. 262. The band and other special units, when attached to the battalion, take the same post with respect to it as if it were the nearest battalion shown in Plate IV. CLOSE ORDER. _Rules._ [Illustration: Plate III. THE BATTALION.]