n rear is (4) the reserve.

In small commands of an infantry regiment or less there usually will
not be any cavalry to cover the front, and the reserve is generally
omitted. Even the support may be omitted and the observation group or
line of groups be charged with checking the enemy, in addition to its
regular duties of observation. But whatever the technical designation
of these subdivisions, the rearmost one is always in fact a reserve.
For example, if the command is so small that the subdivision formally
designated as the reserve is omitted, the rear element (squad or
platoon or company, etc.) is used as a reserve. As this text deals
principally with small commands and only those larger than a regiment
usually have the subdivision termed the reserve, this distinction
between the element in the Field Service Regulations called the
reserve and the actual reserve, must be thoroughly understood.

The arrangements or formations of all detachments thrown out from the
main force to provide security against the enemy, are very flexible,
varying with every military situation and every different kind of
country. The commander of such a detachment must, therefore, avoid
blindly arranging his men according to some fixed plan and at certain
fixed distances. Acquire a general understanding of the principles of
the service of security and then with these principles as a foundation
use common sense in disposing troops for this duty.

ADVANCE GUARD

=1021. Definition and Duties.= An advance guard is a detachment of a
marching column thrown out in advance to protect the main column from
being surprised and to prevent its march from being delayed or
interrupted. (The latter duty is generally forgotten and many
irritating, short halts result, which wear out or greatly fatigue the
main body, the strength of which the advance guard is supposed to
conserve.)

In detail the duties of the advance guard 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 met on the defenses, seize a good position and
locate his lines, care being taken not to bring on a general
engagement unless the advance guard commander is authorized to do so.

5. To remove obst