2.  In case of attack, to check the enemy long enough to enable the main body to make the necessary dispositions.

During an advance the outposts are usually detailed from the advance guard.  During the retreat the outpost for the night usually forms the rear guard the next day.  If the command remains in bivouac, the new outpost generally goes on duty at daybreak.

The vigilance of outpost troops must be unceasing, but they should avoid bringing on combats or unnecessarily alarming the command.  Firing disturbs the rest of troops and, if frequently indulged in, ceases to be a warning.

No trumpet signals except “to arms” or “to horse” are sounded, and all unnecessary noises must be avoided.

As a rule an outpost will not exceed one-sixth the strength of a command.  For a single company a few sentinels and patrols will suffice; for a larger command a more elaborate system must be devised.  The troops composing the outpost are generally divided into a reserve and several supports.

At a proper distance in front of the camp of the main body a line which offers a good defensive position is selected.  This is called the LINE OF RESISTANCE, and should he so located that an advancing enemy will be held in check beyond effective rifle range in case of a small force, artillery range in case of a large force, of the main body until the latter can deploy.  The reserve is stationed at some point in rear of this line, where it can be moved quickly to reinforce any point as needed.  The line of resistance is divided into sections, the limits of each of which are clearly defined.  A support is assigned to each section, which are numbered from right to left, and occupies a position on or near the line, having special regard to covering avenues of approach.  The position occupied should always be intrenched.  The reserve and supports proceed to their respective positions by the shortest routes, providing for their own protection by sending out covering detachments.

Generally speaking, about one-half the Infantry of the advance guard should be in the supports.  As each support arrives at its position it sends out observation groups, varying in size from four men to a platoon, to watch the country in the direction of the enemy.  These groups are called outguards.  For convenience they are classified as pickets, sentry squads, and cossack posts, and should be sufficient in number to cover the front of the section occupied by the support and connect with the neighboring supports.

A picket is a group consisting of two or more squads, ordinarily not exceeding half a company, posted in the line of outposts to cover a given sector.  It furnishes patrols and one or more sentinels, sentry squads, or cossack posts for observation.  Pickets are placed at the more important points in the line of outguards, such as road forks.  The strength of each depends upon the number of small groups required to observe properly its sector.