COMBAT PRINCIPLES.
[342.] The regiment is deployed by the colonel's order to the commanders of battalions and special units. The order should give them information of the situation and of the proposed plan of action. In attack, the order should assign to each battalion not in reserve its objective or line of advance. In defense, it should assign to each its sector. In either case it should designate the troops for, and the position of, the reserve and prescribe the employment of the machine guns and mounted scouts.
Both in attack and defense the order may fix the front to be covered in the deployment.
Encroachment upon the proper functions of subordinates and unnecessary details should be studiously avoided. When the regiment deploys, the colonel habitually places the band at the disposal of the surgeon for employment in caring for the wounded. (C.I.D.R., No. 2.)
[343.] The regiment, when operating alone and attacking, should undertake an enveloping attack if it does not result in overextension.
Assuming a regiment of 1,500 rifles, an extension of more than 1,000 yards between its extreme flanks when making an enveloping attack alone is seldom justifiable; when part of a battle line, a front of 500 yards can rarely be exceeded.
[344.] In defense the front occupied when acting alone or posted on or near the flank of a battle line should seldom exceed 600 yards; when posted as an interior regiment, the front may be increased to 800 yards. The front may be somewhat longer than in the attack, since smaller battalion supports are justifiable. When the regiment is operating alone, however, the regimental reserve should be as strong in the defense as in the attack unless the flanks are secure.
[345.] The colonel should always hold out a reserve—generally one battalion; but when the regiment is operating alone, it is generally advisable to hold out more at first.
[346.] Whereas the support held out in each battalion of the firing line is intended to thicken the diminishing firing line at the proper times and sometimes to lengthen it, the reserve held out in a regiment operating alone is used for this purpose only as a last resort. Its primary functions are: In attack, to protect the flanks, to improve fully the advantage following a victory, or to cover defeat; in defense, to prolong the firing line, to effect a counterattack, or to cover withdrawal. It is the colonel's chief means of influencing an action once begun. It should be conserved to await the proper moment for its employment; the combat will seldom come to a successful issue without its employment in some form.
The reserve of a regiment operating as part of a large force becomes a local reserve. It replaces depleted supports and in attack strengthens and protects the firing line in the charge.