U.S. Department of Defense
The military forces of the United States, along with the civil servants supporting them, form the Department of Defense (also called U.S. Department of Defense and abbreviated to DoD). It is led by a civilian Secretary of Defense appointed by the President and confirmed by the Senate.
Secretary of Defense
The United States Secretary of Defense is a statutory member of the National Security Council and a member of the Cabinet. Robert M. Gates holds the position at this time.
National Command Authority
The President and Secretary of Defense, or their successors, constitute the National Command Authority (NCA). Only the NCA can order the use of nuclear weapons.
History
In 1789 the new U.S. government created a War Department and in 1798 a Navy department, each headed by a cabinet-level secretary. This arrangement reflected the military capabilities of the time (land and sea).
The National Security Act of 1947,[1] created the "National Military Establishment", which joined together the War Department, Department of the Navy and the newly independent Air Force. Its name was changed in 1949 to Department of Defense. The Congressional Act created the Office of the Secretary of Defense, and established civilian positions as the heads of each branch of the military. Secretaries of the Army, Navy, and Air Force were established, each carrying the equivalent rank of Assistant Secretary of Defense. The United States Marine Corps remained a component reporting to the civilian Secretary of the Navy.
The 1947 act also created the National Security Council, Joint Chiefs of Staff, United States Air Force and Central Intelligence Agency. The Air Force celebrates its "birthday" each year based on the date the National Security Act was signed into law.