Its duties are:
(1) To guard against surprise and furnish information by reconnoitering to the front and flanks.
(2) To push back small parties of the enemy and prevent their observing, firing upon, or delaying the main body.
(3) To check the enemy's advance in force long enough to permit the main body to prepare for action.
(4) When the enemy is encountered on the defensive, to seize a good position and locate his lines, care being taken not to bring on a general engagement unless the advance-guard commander is empowered to do so.
(5) To remove obstacles, repair the road, and favor in every way possible the steady march of the column.
STRENGTH AND COMPOSITION
Subject to variation according to the situation, one twentieth to one third of a command may be assumed as a suitable strength for the advance guard. The larger the force, the larger in proportion is the advance guard, for a large command takes relatively longer to prepare for action than a small one. In large commands it is usually composed of all arms, the proportions depending on the nature of the work, character of the country, etc.
DISTANCE FROM THE MAIN BODY
While the distance between these two bodies should be great enough to prevent needless interruptions in the march of the main body, and to give the latter time to deploy should the enemy be encountered, it should never be so great that timely support of the advance guard becomes impracticable.