Arnold, a general in the Army, was the Commanding General of the Army Air Forces throughout World War II, when he was promoted. After his United States Air Force became a separate service on 18 September 1947, Arnold's rank was carried over to the Air Force, just as all Army Air Forces airmen's rank carried over. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.