A mixed outpost is composed principally of infantry. The infantry is
charged with the duty of local observation, especially at night and with
resisting the enemy long enough for the main body to prepare for action.
The cavalry is charged with the duty of reconnaissance, and is very
useful in open country during the day. If the infantry has been severely
taxed by marching or fighting, a large part of the outpost may be
temporarily formed of cavalry.
Artillery is useful to outposts when its fire can sweep defiles or large
open spaces and when it commands positions that might be occupied by
hostile artillery. The guns are carefully concealed or protected and are
usually withdrawn at night.
Machine guns are useful to command approaches and check sudden advances
of the enemy.
The field trains of troops on outpost duty generally join their
organizations; if an engagement is probable, they may be held in rear.