The Group assembled at Blythe Army Airfield, California, and then moved to Geiger Field, Washington, on 20 April 1943 to complete training.

On 20 June 1943 moved to Rapid City Army Air Base, South Dakota, to take up Replacement Training Unit duties.

The 398th BG entered combat in May 1944, and until V-E Day operated primarily against strategic objectives in Germany, attacking targets such as factories in Berlin, warehouses in Munich, marshalling yards in Saarbrücken, shipping facilities in Kiel, oil refineries in Merseburg, and aircraft plants in Münster.

The group temporarily suspended strategic missions to attack coastal defenses and enemy troops on the Cotentin Peninsula during the Invasion of Normandy in June 1944.

The group struck gun positions near Eindhoven in support of the air attack on Holland in September 1944, and raided power stations, railroads, and bridges during the Battle of the Bulge, December 1944 – January 1945.

Among the groups contributions was delivering a United States Marine Corps security forces team.

It provided air refueling missions to fighters in support of Operation Noble Endeavor during the 2008 Bucharest summit.