Office of the Secretary of War

The Office of the Secretary of War was the civilian office that, from 1789, headed the United States Department of War — the executive department responsible for the U.S. Army (and, in its early years, naval affairs and much of the air arm). The War Department existed from August 7, 1789, to September 18, 1947, when the National Security Act of 1947 split it into the Department of the Army and the Department of the Air Force, placed alongside the Department of the Navy within the National Military Establishment. In 1949 that structure was renamed the Department of Defense, and the office of secretary of war was superseded by the secretary of defense. On September 5, 2025, Executive Order 14347, “Restoring the United States Department of War,” authorized “Department of War” and “Office of the Secretary of War” as secondary (non-statutory) titles for the Department of Defense and the Office of the Secretary of Defense, respectively; the statutory names retain “Defense,” and only an act of Congress can change them formally. The department began using the “Department of War” name publicly, including moving its website to the war.gov domain. Its headquarters is the Pentagon in Arlington County, Virginia.