order of the commander of a covering detachment should clearly
explain the situation to subordinates, assign the troops to the
subdivisions, prescribe their distances, and order such special
reconnaissance as may be deemed necessary in the beginning.

An advance or flank guard commander marches well to the front and,
from time to time, orders such additional reconnaissance or makes such
changes in his dispositions as the circumstances of the case demand.

_Advance Guards._

639. An _advance guard_ is a detachment of the main body which
precedes and covers it on the march.

640. The advance guard commander is responsible for its formation and
conduct. He should bear in mind that its purpose is to facilitate and
protect the march of the main body. Its own security must be effected
by proper dispositions and reconnaissance, not by timid or cautious
advance. It must advance at normal gait and search aggressively for
information of the enemy. Its action when the enemy attempts to block
it with a large force depends upon the situation and plans of the
commander of the troops.

641. The strength of the advance guard varies from one-twentieth to
one-third of the main body, depending upon the size of the main body
and the service expected of the advance guard.

642. The formation of the advance guard must be such that the enemy
will be met first by a patrol, then in turn by one or more larger
detachments, each capable of holding the enemy until the next in rear
has time to deploy before coming under effective fire.

643. Generally an advance guard consisting of a battalion or more is
divided primarily into the _reserve_ and the _support_. When the
advance guard consists of less than a battalion, the reserve is
generally omitted.

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