“As a command on the march protects itself from surprise by covering detachments called advance guards, flank guards and rear guards, so also does a command at a halt protect itself by a system of covering detachments denominated outposts.
“Duties.—Like advance guards on the march, the outpost is charged with the duties of observation and resistance.
“Specifically these duties are:
“1. To protect the main body so that the troops may rest undisturbed.
“2. In case of attack, to check the advance of the enemy long enough to enable the main body to make dispositions to meet him.
“3. To reconnoiter the enemy, prevent his reconnaissance and give timely warning of the approach of hostile bodies.
“Subdivisions.—The outpost is divided into two general lines. The first, which is called the ‘line of observation,’ does the watching for the enemy and prevents his small bodies from getting any information about our troops or annoying them. The second is a ‘fighting line,’ which holds off larger bodies.
“These lines must cover the front and flanks of the troops at rest. The ‘watching line’ must be so located that the watchers out in front will be able to see the enemy before he gets close enough to do damage. The ‘fighting line’ must be so located that it will have what we call a ‘good field of fire;’ that is, the ground in front must not be such that it will hide the movements of the enemy and allow him to get within effective rifle range without coming under our fire.
“Formation.—The formation of an outpost may best be described by referring to an outstretched hand.
“Hold your left hand in front of you with the thumb and fingers extended and pointing to the front, palm of hand down.