Didn’t the DOD used to be called the Dept. Of War?
https://en.wikipedia.org/wiki/United_States_Department_of_War
The War Department existed from August 7, 1789 until September 18, 1947,[1] when it split into the Department of the Army and the Department of the Air Force. The Department of the Army and Department of the Air Force later joined the Department of the Navy under the United States Department of Defense in 1949.