Constituted 14 September 1943 and activated 20 September 1943 at Ephrata Army Air Base (AAB), Washington. Assigned to 483d Bombardment Group (Heavy) 20 September 1943. Stations: MacDill Army Air Field (AAF), Florida 7 November 1943; Tortorella, Italy, 2-4 March 1944; Sterparone Air Field, Italy, 9 April 1944; Pisa, Italy, 15 May 1944. Group and squadron inactivated 25 September 1945 in Italy. Equipped with B-17 aircraft. 483d BG(H) assigned to Fifteenth Air Force in Italy. Combat Operations, European (ETO) and Mediterranean (MTO) Theaters of Operations 12 April 1944 to 26 April 1945. Air strikes directed at factories, oil refineries, railroad marshalling yards, storage areas, airdromes, bridges, gun positions and troop concentrations in Italy, France, Germany, Poland, Czechoslovakia, Austria, Hungary, Rumania, Yugoslavia and Greece. Struck targets in Southern France in preparation for the invasion, August 1944. After surrender (VE Day) transported American air and ground personnel from Italy to North Africa for return to the United States. Presidential Unit Citation (PUC) for raid on airdrome and other installations at Memmingen, Germany, 18 July 1944. Presidential Unit Citation (Second Award) for raid on tank and armored vehicle factories at Berlin, Germany, 24 March 1945. Campaign participation credits (12): Air Offensive, Europe; Rome-Arno; Normandy (Invasion); Normandy (Campaign); Northern France; Southern France (Invasion); Southern France (Campaign); Northern Appenines; Rhineland; Central Europe; Po Valley and Air Combat, European-African-Middle Eastern Theater.
483d Bombardment Group (Heavy) consisted of 815th, 816th, 817th and 818th (redesignated 840th 15 February 1944) Bombardment Squadrons (Heavy). Group commanders were Colonel Paul L. Barton (20 September 1943 to 7 May 1945) and Colonel Joseph B. Stanley (8 May to 25 September 1945).