Envelopment

Envelopment is the military tactic of surrounding an enemy in the field so that they are isolated in a pocket. The friendly forces can choose to attack the pocket or invest it (to stop supplies getting and to prevent breakouts) and wait for a beleaguered enemy to surrender.

To achieve an envelopment several different tactics can be employed:
 * A flanking maneuver can envelop an enemy force if some form of obstacle (such as a river, sea, or a mountain range) prevents the enemy from retreating or obtaining supplies.
 * A pincer movement consists of two simultaneous flanking maneuvers which encircle an enemy. Early in World War II the Germans frequently employed this tactic and encircled huge numbers of the enemy during the Blitzkrieg attacks on both the Western Front during the Battle of France and during Operation Barbarossa on the Eastern Front.
 * A retreat where the enemy advances and then is attacked by friendly forces in the rear as happened at the Battle of Cannae.
 * A vertical envelopment is "a tactical maneuver  in which troops, either air-dropped or air-landed, attack the rear and flanks of a force, in effect cutting off or encircling the force".