Halesworth airfield was built as a Class A bomber base. Its close proximity to the North Sea provided an ideal launch site for missions deep into Europe. Construction of its three runways, two hangars and accommodation for some 3000 personnel began in 1942. By July the airfield saw its first operational unit. However, instead of bombers, the 56th Fighter Group of the United States 8th Army Air Force were stationed there.
Using its prime position and size the 56th became one of the leading fighter groups in the 8th and by the end of the war was one of the most successful in aerial combat. They left Halesworth in April 1944.
A month later the 489th Bomb Group arrived and flew its first mission just before June. Flying B24 Liberators they played a full part in the build up to and during D Day on 6th June 1944. From July they switched to strategic offensive bombing until November, when they ceased operations to return to America.
Between January and June in 1945 the 5th Emergency Rescue Squadron operated from the base flying war-weary P47s and B17s. Their mission was to carry dinghies and smoke markers to aid downed crews found at sea. The 5th ERS also flew the OA-I0A Catalina flying boats. During this time 496th Fighter Training group shared the base flying the P51 Mustang.
In June 1945 Royal Air Force Bomber Command gained control of the base, before it was handed over to the Royal Navy in early August to be used as an advanced flying training base, HMS Sparrowhawk.