The War Department was an executive department of the United States government from 1789 to 1947, when its name was changed and it was reorganized. It was created to supervise all military functions and aspects of national defense.
In 1798, Congress separated the Navy from the Army, which created a new Department of the Navy. The War Department continued to supervise the Army. Both department secretaries were answerable to the president, were members of his Cabinet, and cooperated in joint committees and conferences.