United States Department of the Army | 15,551 followers on LinkedIn. One of the three military departments within the Department of Defense of the United States of America. | The 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 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. The Secretary of the Army is a civilian official appointed by the President and confirmed by the Senate.