The United States Department of Defense/Defence is responsible for coordinating and supervising all agencies and functions of the government concerned directly with national security and the armed forces. The department is headed by the Secretary of Defense/Defence, who is a civilian and a member of the President’s Cabinet.
The Department of Defense was established by the National Security Act of 1947, which created a unified military command under the President. The act also created the National Security Council, to advise the President on matters related to national security. The first Secretary of Defense was James Forrestal, who served from 1947 until 1949.
Since its establishment, DOD has been involved in many major conflicts including World War II, Korea, Vietnam War, Persian Gulf War, and Afghanistan. In recent years it has also been tasked with combating terrorism and supporting relief efforts following natural disasters such as Hurricane Katrina.