Renamed Charleston Army Air Field on 15 June 1943, initially the base served mainly as an air depot training station, providing the final phase of training to service groups and air depot groups departing home for the war overseas. Concurrent with its reassignment to First Air Force, in September 1943 the base changed missions. Now it would give the final phase of training to B-24 Liberator crews. The 454th Bombardment Group arrived in September and left Charleston for the European Theater of Operations in December 1943. This same month the 400th Bombardment Group arrived, but this organization was to function as a replacement training unit rather than an operational training unit.