The group was an Eighth Air Force fighter unit stationed in England assigned to RAF Fowlmere.

On the first of those days, when it escorted bombers to a target in Germany and then attacked an aerodrome near Erding, the group destroyed or damaged many enemy planes despite the intense fire it encountered from anti-aircraft guns and small arms.

The following day the bomber formation being escorted to Munich was attacked by enemy fighters, but members of the 339th group destroyed a number of the interceptors and drove off the others and at the same time, other members of the 339th were attacking an airfield near Karlsruhe, where they encountered heavy fire but were able to destroy or damage many of the aircraft parked on the field.

[citation needed] The 339th provided fighter cover over the English Channel and the coast of Normandy during the invasion of France in June 1944.

They strafed and dive-bombed vehicles, locomotives, marshalling yards, anti-aircraft batteries, and troops while Allied forces fought to break out of the beachhead in France.