The 615th Bombardment Squadron was activated March 1943 at Ephrata Army Air Base Washington as one of the original squadrons of the 401st Bombardment Group. The initial cadre for the squadron was drawn from the 395th Bombardment Group at Ephrata and the 383d Bombardment Group at Rapid City Army Air Field, South Dakota. The cadre soon departed for Orlando Army Air Base, Florida, where they conducted simulated combat missions with the Army Air Forces School of Applied Tactics out of Brooksville Army Air Field.