The United States Department of War, also called the War Department, was the United States Cabinet department originally responsible for the operation and maintenance of the United States Army, also bearing responsibility for naval affairs until the establishment of the Navy Department in 1798, and for most land-based air forces until the creation of the Department of the Air Force on September 18, 1947.

The Cabinet of the United States is the principal official advisory body to the president of the United States. The Cabinet meets with the president in a room adjacent to the Oval Office. The president chairs the meetings but is not formally a member of the Cabinet. The heads of departments, appointed by the president and confirmed by the Senate, are members of the Cabinet, and acting department heads also participate in Cabinet meetings whether or not they have been officially nominated for Senate confirmation. The president may designate heads of other agencies and non-Senate-confirmed members of the Executive Office of the President as members of the Cabinet.