The 539th Fighter Squadron was activated in October 1943 at Westover Field, Chicopee, Mass in October 1943. Shortly after activation, the squadron moved to Seymour Johnson Field, Goldsboro, North Carolina to become part of the 402nd Fighter Group where it operated under the Replacement Training Unit Program of the advanced phase of pilot training. In December 1943, the squadron again moved, this time to Blumenthal Field, Wilmington, North Carolina, and was assigned to the 326th Fighter Group where it remained until disbanded in April 1944.