The question of how best to organize the United States Army's air arm had been contentious from the time of the First World War. Legislation to give the air arm greater autonomy or even independence had been introduced in the Congress in the interwar years. Although independence would not be achieved until after World War II, the air arm during the interwar period made remarkable progress towards this goal. In 1926 the Army Air Corps was established, and in 1934 the Baker Board directed the formation of the General Headquarters Air Force, giving the Army air arm a measure of autonomy. On the eve of the Second World War, the War Department created the Army Air Forces. Although falling short of independence, these were important steps forward on the road to the creation of today's global Air Force. R. Earl McClendon's classic Autonomy of the Air Arm describes the Army air arm's struggle for autonomy over almost forty years, from 1907 to the close of World War II McClendon's narrative details the contentious evolution of the Army Air Forces (AAF) in March 1942 as a fully coequal branch with the Army Ground Forces (AGF). Following the end of the war, President Harry S. Truman firmly positioned himself in favor of "air parity" and an independent Air Force. Mcclendon emphasizes that "for the first time in the history of American aviation the Commander-in-Chief of the armed forces definitely took a stand in favor of an independent military air arm." Truman's firm leadership on this issue ultimately resulted in passage of the National Security Act of 1947. After four decades of prolonged gestation, the United States Air Force was born.