The military chain of command flows from the president of the United States to the secretary of defense (for services under the Defense Department) or secretary of homeland security (for services under the Department of Homeland Security), ensuring civilian control of the military. Within the Department of Defense the military departments, the Department of the Army, United States Department of the Navy, and Department of the Air Force, are civilian led entities that oversee the coequal military service branches organized within. The military departments and services are responsible for organizing, training, and equipping forces, with the actual chain of command flowing through the unified combatant commands.