DOD operates six geographic combatant commands, each with an assigned area of responsibility (see fig. 1). Each geographic combatant command carries out a variety of missions and activities, including humanitarian assistance and combat operations, and assigns functions to subordinate commanders. Each command is supported by a service component command from each of the services and by a theater special operations command. The Departments of the Army, Navy, and Air Force have key roles in making decisions on where to locate their forces when they are not otherwise employed or deployed by order of the Secretary of Defense or assigned to a combatant command.