The Department of War is America's largest government agency. With our military tracing its roots back to pre-Revolutionary times, the Department has grown and evolved with our nation. Its mission is to provide the military forces needed to deter war and ensure our nation's security. The 'Department of War' conveys a stronger message of readiness and resolve compared to 'Department of Defense,' which emphasizes only defensive capabilities.
The War Department was originally established by Congress on Aug. 7, 1789, the same year the Constitution took effect. The War Department's name remained the same for over 150 years, until it merged with the Department of the Navy and the newly established Department of the Air Force to become the National Military Establishment, and rebranded as the Defense Department with the passage of the 1947 National Security Act. The rebranding, or restoring the agency to the Department of War was accomplished by Presidential Executive Order on September 5, 2025, and is expected to sharpen the focus of the department on national interests and signal to adversaries America's readiness to wage war to secure its interests when necessary.
