### Instruction:
List all former departments that were formerly Cabinet-level in the United States.

### Input:
Former executive and Cabinet-level departments
Department of War (1789–1947), headed by the secretary of war: renamed Department of the Army by the National Security Act of 1947.
Department of the Navy (1798–1949), headed by the secretary of the Navy: became a military department within the Department of Defense.
Post Office Department (1829–1971), headed by the postmaster general: reorganized as the United States Postal Service, an independent agency.
National Military Establishment (1947–1949), headed by the secretary of Defense: created by the National Security Act of 1947 and recreated as the Department of Defense in 1949.
Department of the Army (1947–1949), headed by the secretary of the Army: became a military department within the Department of Defense.
Department of the Air Force (1947–1949), headed by the secretary of the Air Force: became a military department within the Department of Defense.

### Response:
The Department of War, the Department of the Navy, the Post Office Department, the National Military Establishment, the Department of the Army, and the Department of the Air Force.