Army one of five US armed service branches. Army the dominant land power. The Army generally moves in to an area, secures it, and instills order and values before it leaves. It also guards U.S. installations and properties throughout the world.
As the oldest branch of the U.S. Military, founded in 1775, the Army is a powerful fighting force defending and serving our nation by land, sea and air. Elite groups within the Army, such as the Army Rangers and Special Forces, receive specialized training for advanced combat situations.