The Pentagon is seen on Oct. 21, 2021. (Robert H. Reid/Stars and Stripes)

Happy 74th birthday to the U.S. Department of Defense, which was officially established Aug. 10, 1949.

While that may seem a bit young for the government agency that oversees the U.S. Armed Forces, the DOD’s roots go back to the Revolutionary War and the establishment of the War Department in 1789.

The National Security Act of 1947 created the National Military Establishment, merging the War Department, Navy Department and the Department of the Air Force. In 1949, the National Military Establishment officially became the DOD, with the secretary of defense given more power over individual services, according to the Office of the Historian.

Today the DOD, housed in the Pentagon in Arlington, Va., is the largest government agency, employing 3.4 million service members and civilians according to its website. The Army, Navy, Marine Corps, Air Force and Space Force fall under its jurisdiction, with the Army and Air National Guards operating in part under state authority. The DOD has 11 combatant commands, each with its own geographic or functional mission.