To intercept a corps and prevent its junction with the main body
of the enemy, or to facilitate the approach of your own
reinforcements.
To observe and hold in position a large portion of the opposing
army, while a blow is struck at the remainder.
To carry off a considerable convoy of provisions or munitions,
on receiving which depended the continuance of a siege or the
success of any strategic enterprise, or to protect the march of a
convoy of your own.
To make a demonstration to draw the enemy in a direction where
you wish him to go, in order to facilitate the execution of an
enterprise in another direction.
To mask, or even to invest, one or more fortified places for a certain time, with a view either to attack or to keep the garrison shut up