President Donald Trump has announced that his administration will begin referring to the Defense Department as the “Department of War,” a title historically used when the agency’s responsibilities were far narrower, overseeing primarily the U.S. Army.
The Defense Department, as it is officially known today, was created by an act of Congress following World War II. Because its name is set in federal law, the president does not have the authority to formally change it without congressional approval. To sidestep this limitation, the White House explained that Trump has authorized the use of “Department of War” as an informal or secondary designation within his administration.
Origins Over Two Centuries Ago
The War Department was originally established in August 1789, tasked with overseeing the Army, Navy, and Marine Corps, according to official Pentagon records. Less than ten years later, in 1798, naval operations were transferred to the newly created Department of the Navy, which also assumed responsibility for the Marine Corps in 1834. From that point forward, the War Department managed the Army and eventually the Army Air Corps, which later evolved into the U.S. Air Force.
Major Post-WWII Reorganization
After World War II, America’s military command underwent sweeping structural changes. In July 1947, President Harry Truman signed the National Security Act, merging the War Department, the Navy Department, and the newly created Air Force into a single body known as the “National Military Establishment.” The act also introduced the position of Secretary of Defense to provide unified civilian leadership.
Two years later, in August 1949, Congress amended the legislation, renaming the National Military Establishment as the Department of Defense — the title that remains in place today.
