owever, the direction
of march of the column is such that there is a great danger of the
enemy's striking it in flank and some special provision is necessary
to furnish additional security on the threatened flank. This is done
by having a detachment, called a flank guard, march off the exposed
flank. The flank guard usually follows a road, parallel to the one on
which the column is marching and at least 1,000 yards (effective rifle
range) beyond it. If hostile artillery is feared this distance is much
greater.

The flank guard regulates its march so as to continue abreast of the
advance guard of the main column. It takes a formation similar to an
advance guard, does most of its patrolling to the front and on the
exposed flank, and keeps in constant touch with the main column by
means of mounted or dismounted messengers.

In case the enemy is encountered the flank guard drives him off if
practicable or takes up a defensive position, protecting the march of
the main column, and preventing the enemy from disturbing the latter's
march.

REAR GUARD

=1047. Definition and Duties.= A rear guard is a detachment of a
marching column following in rear to protect the main column from
being surprised and to prevent the march from being delayed or
interrupted.

When the main column is marching toward the enemy the rear guard is
very small and its duties relatively unimportant. It is principally
occupied in gathering up stragglers.

When the main column is marching away from the enemy (retreating) the
rear guard is all important. It covers the retreat of the main body,
preventing the enemy from harassing or delaying its march.

=1048. Strength.= The strength of a rear guard is slightly greater
than that of an advance guard, as it cannot expect, like the latter,
to be reinforced in case it is attacked, as the main column is
marching away from it and avoiding a fight.

=1049. Form of Order.= The rear guard commander, on the receipt of the
retreat order, issues a rear guard order, according to the form given
in the Field Service Regulations.

The distance of a rear guard from the main body and its formation are
similar to those of an advance guard. The elements corresponding to
the advance cavalry, the point, and the advance party of an advance
guard are termed the rear cavalry, rear point and rear party,
respectively. The support and reserve retain the same designations.

A rear guard formed during an engagement to cove