No. The Department of Defense didn't exist before 1947. The Department of War was the original name of the Department of the Army, which was separate from the Department of the Navy.
Trump signed an executive order on Friday to rebrand the Department of Defense as the Department of War, a callback to the department’s original name used from 1789 to 1947.
Trump signs executive order rebranding Pentagon as Department of War
Directive will make Department of War secondary title and is way to get around need for congressional approval