American aviation development fell behind its European rivals after the mid-1930s when Germany started a continental arms race. The threat of war at the decade's end began to change the situation. During the late 1930s American industry spent over $100 million annually on aviation research. University grants grew and military personnel enrollment in science courses increased. Leaders of the Army Air Forces (AAF) were alarmed by many of the new weapons that would revolutionize air warfare which had emerged from foreign laboratories. Radar, jet aircraft (Messerschmitt Me 262, Fieseler Fi 103 (V-1 flying bomb)) and ballistic missiles (V-2 rocket) had all either originated or been perfected outside the United States. Congress greatly increased funds for R&D. Subsequently, the engineering function resided in the Materiel Command, the AAF Technical Service Command, the Air Technical Service Command, and the Air Materiel Command.