separation - the act of dividing or disconnecting

retreat - (military) withdrawal of troops to a more favorable position to escape the enemy's superior forces or after a defeat; "the disorderly retreat of French troops"

armed forces, armed services, military, military machine, war machine - the military forces of a nation; "their military is the largest in the region"; "the military machine is the same one we faced in 1991 but now it is weaker"