Department of Defense

Headquartered in the Pentagon, one of the world's largest office build­ings, the Department of Defense (DoD) is responsible for all matters relating to the nation's military secu­rity. It provides the military forces of the United States, which consist of about 1 million men and women on active duty. They are backed, in case of emergency, by 1.5 million mem­bers of state reserve components, known as the National Guard. In addition, about 730,000 civilian employees serve in the Defense Department in such areas as research, intelligence communica­tions, mapping, and international security affairs. The National Security Agency, which coordinates, directs, and performs highly special­ized intelligence activities in support of U.S. government activities, also comes under the direction of the sec­retary of defense.

The department directs the separate­ly organized military departments of the Army, Navy, Marine Corps, and Air Force, as well as the four military ser­vice academies and the National War College, the Joint Chiefs of Staff, and several specialized combat commands. DoD maintains forces overseas to meet treaty commitments, to protect the nation's outly­ing territories and com­merce, and to provide air combat and support forces. Nonmilitary responsibili­ties include flood control, develop­ment of oceanographic resources, and management of oil reserves.