=645.= At the first indication for the charge the ground scouts move out from the flanks of the attacking line (par. 569) unless otherwise specially directed. The captain usually sends out any necessary combat patrols; but each leader of a separate group is responsible that any further steps necessary for the immediate protection of his own flanks are taken. THE TROOP IN THE SQUADRON. =646.= The troop in squadron, in mounted attack, has no reserve, but may have a support in the discretion of the major. If on the flank of the squadron, its own flank defense must be provided by the captain in the absence of instructions. PASSING FROM MOUNTED ACTION TO DISMOUNTED ACTION. =647.= The movements are executed by commands and methods corresponding to those already explained for the squad and platoon, with the following modifications and additions thereto: The horses of the captain and of one bugler who accompanies the captain are held by the other bugler or by a man specially designated _in advance_ for that duty. The horses of the first sergeant and other men out of ranks, and not otherwise specially provided for, are secured in the same manner indicated in the corresponding provisions for the squad and platoon. =648.= The guidon, in the absence of instructions to the contrary, takes general charge of the led horses and performs the duties prescribed for the trooper in charge of the horse-holders and horses (par. 431). Should one of the platoon file closers be senior to the guidon, the first sergeant cautions such file closer and the guidon _in advance_ that the senior will have general charge of the led horses of the troop while such senior remains with the horses. In the absence of other special instructions, the file closer of each platoon reports the additional troopers of his platoon to the troop commander after Nos. 2 dismount. The guidon remains in general charge of the other horse-holders and the horses, a designated trooper having, under the guidon, immediate charge of the horse-holders and horses of each platoon.