United States Department of War

The United States Department of War, also called the War Department (and occasionally War Office in the early years), was the United States Cabinet department responsible for the operation and maintenance of the United States Army. It also had responsibility for naval affairs from 1794 until the establishment of the Department of the Navy in 1798, and for most non-naval air forces until the creation of the Department of the Air Force on September 18, 1947.

Source: Wikipedia — United States Department of War (CC BY-SA 4.0)