HQDA meaning in Governmental ?

The United States Department of the Army (DA) is one of the three military departments within the Department of Defense of the U.S.. The Department of the Army is the federal government agency within which the United States Army (U.S.) is organized, and it is led by the secretary of the Army, who has statutory authority under 10 United States Code § 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. The highest-ranking military officer in the department is the chief of staff of the Army, who is also a member of the Joint Chiefs of Staff. Other senior officials of the department are the under secretary of the Army (principal deputy to the secretary) and the vice chief of staff of the Army (principal deputy to the chief of staff.)

The Department of War was originally formed in 1789 as an Executive Department of the United States, and was split by the National Security Act of 1947 into the Department of the Army and Department of the Air Force on September 18, 1947. By amendments to the National Security Act of 1947 in 1949, the department of the Army was transformed to its present-day status.