On June 20, 1941, the Department of War created the Army Air Forces to replace the Army Air Corps, including the aerial reconnaissance capability. At the time of Adolf Hitler’s 1939 invasion of Poland, the AAC – which was created in 1926 and housed the majority of America’s air power – had 20,000 personnel and less than 2,400 planes. Hitler’s continued hostility and the surprise Japanese attack of Pearl Harbor accelerated the expansion of the U.S. air capability to previously unseen levels.
According to U.S. Air Force historical records, during World War II, the Army Air Forces oversaw mobilization of the nation's aviation industry and deployment of the largest air armada of all time. The AAF reached a peak strength of 80,000 aircraft and 2.4 million personnel organized into major commands, numbered air forces, air divisions, groups and squadrons.
The growth of the AAF also meant an increase in the War Department’s aerial reconnaissance capability. Between 1942 and 1945, the USAAF reconnaissance force grew from 475 aircraft to a wartime peak of 2,000. In February 1945, 13 of the 243 USAAF combat groups focused solely on reconnaissance.
On September 18, 1947, the U.S. Air Force subsumed both the Army Air Corps and Army Air Forces as an independent military service.