A military prison is a prison operate by the military. Military prisons are used variously to house prisoners of war, enemy combatants, those whose freedom is deemed a national security risk by military or civilian authorities, and members of the military found guilty of a serious crime. Thus military prisons are of two types: penal, for punishing and attempting to reform criminals within the military, and confinement-oriented, where captured enemies are confined for military reasons until hostilities cease.