[644.] In an advance guard consisting of two battalions or less, the reserve and support, if both are used, are approximately equal; in larger advance guards, the reserve is approximately two-thirds of the whole detachment.
In an advance guard consisting of one battalion, the machine guns, if any, form part of the reserve. In an advance guard consisting of two or more battalions, the machine guns form part of the support.
[645.] The support sends forward an advance party. The advance party, in turn, sends a patrol, called a point, still farther to the front. Patrols are sent out to the flanks when necessary. When the distance between parts of the advance guard or the nature of the country is such as to make direct communication difficult, connecting files march between the subdivisions to keep up communication. Each element of the column sends the necessary connecting files to its front.
[646.] A battalion acting as an advance guard should be formed about as follows: The reserve, two companies; the support, two companies; the advance party, three to eight squads (about a half company), depending upon the strength of the companies and the reconnaissance to be made; the point, a noncommissioned officer and three or four men. Or the reserve may be omitted. In such case the advance party will consist of one company preceded by a strong point. The remaining companies form the support.
[647.] The distances separating the parts of an advance guard vary according to the mission of the whole force, the size of the advance guard, the proximity and character of the enemy, the nature of the country, etc. They increase as the strength of the main body increases; they are less when operating in rolling, broken country than in open country; when in pursuit of a defeated enemy than against an aggressive foe; when operating against cavalry than when against infantry.
If there be a mounted point, it should precede the dismounted point by 250 to 600 yards. The advance party may be stronger when there is a mounted point in front. The infantry maintains its gait without reference to the mounted point, the latter regulating its march on the former, (C.I.D.R., No. 2.)
[648.] To afford protection to an infantry column, the country must be observed on each side of the road as far as the terrain affords positions for effective rifle fire upon the column. If the country that it is necessary to observe be open to view from the road, reconnaissance is not necessary.
[649.] The advance guard is responsible for the necessary reconnaissance of the country on both sides of the line of march.
Special reconnaissance may be directed by the commander of the troops, or cavalry may be reconnoitering at considerable distances to the front and flanks, but this does not relieve the advance guard from the duty of local reconnaissance.
[650.] This reconnaissance is effected by patrols sent out by the leading subdivisions of the advance guard. In a large advance guard the support commander orders the necessary reconnaissance.