The squadron was activated in late March 1943 at Drew Field, Florida as the 634th Bombardment Squadron, one of the four original squadrons of the 407th Bombardment Group. The squadron was equipped with Douglas A-24 Banshees. In July, the squadron's air echelon deployed to Amchitka Army Air Field, Alaska to reinforce Eleventh Air Force in Operation Cottage, an attack on Kiska, the last Japanese outpost in the Aleutian Islands. The first combat sorties by elements of the 407th Group were flown on 4 August 1943, in an attack against antiaircraft artillery batteries in the main Japanese camp. The returning crews reported only meager small arms and light automatic weapons fire. As it turned out, the Japanese had decided to evacuate Kiska, leaving the United States in control of the Aleutians, and the squadron was returned to its training base in Florida, under its new name, the 517th Fighter-Bomber Squadron.