[358]. Trenches. The major locates such fire, communicating, and cover trenches and obstacles as are to be constructed. He assigns companies to construct them and details the troops to occupy them. (See "Field Fortifications," Chapter XVI, Part III.) (321)
[359]. Reënforcement of firing line. The major reënforces the firing line in accordance with the principles applicable to and explained in connection with, the attack, in [pars. 352]–354, maintaining no more rifles in the firing line than are necessary to prevent the enemy's advance. (322)
[360]. Opening fire. The supply of ammunition being usually ample, fire is opened as soon as it is possible to break up the enemy's formation, stop his advance or inflict material loss, but this rule must be modified to suit the ammunition supply. (323)
[361]. Fixing bayonets. The major causes the firing line and support to fix bayonets when an assault by the enemy is imminent. Captains direct this to be done if they are not in communication with the major and the measure is deemed advisable.
Fire alone will not stop a determined, skillfully conducted attack. The defender must have equal tenacity; if he can stay in his trench or position and cross bayonets, he will at least have neutralized the hostile first line, and the combat will be decided by reserves. (324)
[362]. Support to cover withdrawal. If ordered or compelled to withdraw under hostile infantry fire or in the presence of hostile infantry, the support will be posted so as to cover the retirement of the firing line (325)
[363]. Support in case of battalion acting alone. When the battalion is operating alone, the support must be strong and must be fed sparingly into the firing line, especially if a counter-attack is planned. Opportunities for counter-attack should be sought at all times, as explained in [pars. 525]–530. (326)
COMBAT
INTRODUCTION
[364]. Scope of subject of combat tactics in this book. Part II of these regulations treats only of the basic principles of combat tactics as applied to infantry and to the special units, such as machine guns and mounted scouts, which form a part of infantry regiments and battalions.