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Defense Department

Office Of The Secretary, Joint Chiefs Of Staff, The Department Of Defense In The Response To TerrorismStructure

The Department of Defense (DOD) is the executive department in the federal government that is responsible for providing the military forces needed to deter war and to protect the security of the United States. The major elements of the military forces under its control are the Army, Navy, Air Force, and Marine Corps, consisting of about 1.5 million men and women on active duty. They are backed, in case of emergency, by 1 million members of reserve units. In addition, the DOD employs approximately nine hundred thousand civilians.

Although every state has some defense activities, the central headquarters of the DOD is in northern Virginia at the Pentagon, the "world's largest office building."

The National Security Act of 1947 (50 U.S.C.A. § 401) created the National Military Establishment, which replaced the War Department and was later renamed the Department of Defence. It was established as an executive department of the government by the National Security Act Amendments of 1949, with the secretary of defense as its head (5 U.S.C.A. § 101). Since 1949, many legislative and administrative changes have occurred, evolving the department into the structure under which it currently operates.


The DOD includes the Office of the Secretary of Defense, the military departments and the military services within those departments, the chair of the Joint Chiefs of Staff and the Joint Staff, the unified combatant commands, the DOD agencies, the DOD field activities, and such other offices, agencies, activities, and commands as may be established or designated by law or by the president or the secretary of defense.


Defense LINK-Official Web Site of the US Department of Defense. Available online at <www.defenselink.mil> (accessed November 20, 2003).

U.S. Government Manual Website. Available online at <www.gpoaccess.gov/gmanual> (accessed November 10, 2003).

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