The fraction making the rush should be as large as the hostile fire and the necessity for maintaining fire superiority will permit. Depending upon circumstances, the strength of the fraction may vary from a company to a few men. The advance is made as rapidly as possible without losing fire superiority. The smaller the fraction which rushes, the greater the number of rifles which continue to fire upon the enemy. On the other hand, the smaller the fraction which rushes the slower will be the progress of the attack. 310. Enough rifles must continue in action to insure the success of each rush. Frequently the successive advances of the firing line must be effected by rushes of fractions of decreased size; that is, advances by rushes may first be made by company, later by half company or platoon, and finally by squads or files; but no subsequent opportunity to _increase_ the rate of advance, such as better cover or a decrease of the hostile fire, should be overlooked. 311. Whenever possible, the rush is begun by a flank fraction of the firing line. In the absence of express directions from the major, each captain of a flank company determines when an advance by rushes shall be attempted. A flank company which inaugurates an advance by rushes becomes the base company, if not already the base. An advance by rushes having been inaugurated on one flank, the remainder of the firing line conforms; fractions rush successively from that flank and halt on the line established by the initial rush. The fractions need not be uniform in size; each captain indicates how his company shall rush, having due regard to the ground and the state of the fire fight. 312. A fraction about to rush is sent forward when the remainder of the line is firing vigorously; otherwise the chief advantage of this method of advancing is lost. The length of the rush will vary from 30 to 80 yards, depending upon the existence of cover, positions for firing, and the hostile fire. 313. When the entire firing line of the battalion has advanced to the new line, fresh opportunities to advance are sought as before. 314. Two identical situations will never confront the battalion; hence at drill it is prohibited to arrange the details of an advance before the preceding one has been concluded, or to employ a fixed or prearranged method of advancing by rushes. 315. The major posts himself so as best to direct the reenforcing of the firing line from the support. When all or nearly all of the support has been absorbed by the firing line, he joins, and takes full charge of, the latter. 316. The reenforcing of the firing line by driblets of a squad or a few men has no appreciable effect. The firing line requires either no reenforcement or a strong one. Generally one or two platoons will be sent forward under cover of a heavy fire of the firing line.