United States Department of the Army

The United States Department of the Army (DA) is one of the three military departments within the Department of Defense of the United States of America. The Department of the Army is the federal government agency within which the United States Army (USA) is organized, and it is led by the secretary of the Army, who has statutory authority under 10 U.S.C. § 3013 to conduct its affairs and to prescribe regulations for its government, subject to the limits of the law, and the directions of the secretary of defense and the president.

Source: United States Department of the Army on Wikipedia.