Constituted as 323rd Bombardment Group (Medium) on 19 June 1942. Activated on 4 Aug. 1942. Trained with B-26's. Moved to England, April-June 1943. Assigned first to Eighth AF and, in Oct. 1943, to Ninth AF. Began operations in July 1943, attacking marshalling yards, airdromes, industrial plants, military installations, and other targets in France, Belgium, and Holland. Then carried out numerous attacks on V- weapon sites along the coast of France.
Attacked airfields at Leeuwarden and Venlo in conjunction with the Allied campaign against the German Air Force and aircraft industry during Big Week, 20-25 Feb. 1944. Helped to prepare for the invasion of Normandy by bombing coastal batteries on 6 June 1944. Participated in the aerial barrage that assisted the breakthrough at St. Lo in July. Flew its first night mission after moving to the Continent in Aug., striking enemy batteries in the region of St. Malo. Carried out other night missions during the month to hit fuel and ammunition dumps. Eliminated strong points at Brest early in Sept. and then shifted operations to eastern France to support advances against the Siegfried Line. Received a DUC for actions (24-27 Dec. 1944) during the Battle of the Bulge when the group effectively hit transportation installations used by the enemy to bring reinforcements to the Ardennes. Flew interdictory missions into the Ruhr and supported the drive into Germany in May to participate in the disarmament program. Returned to the US in Dec. Inactivated on 12 Dec. 1945.
Redesignated 323rd Fighter-Bomber Group. Activated on 8 Aug. 1955. Assigned to Tactical Air Command.