504th Bombardment Group

504th Bombardment Group
504th Bombardment Group Insignia
Active	1944–1946
Country	United States
Branch	United States Army Air Forces
Role	Bombardment
Part of	Twentieth Air Force
Garrison/HQ	Pacific Ocean Theater of World War II
Engagements	World War II Asiatic-Pacific Campaign (1944–1945)

The 504th Bombardment Group (504th BG) was a World War II United States Army Air Forces combat organization. It was inactivated on 15 June 1946.

The unit served primarily in the Pacific Ocean theater of World War II as part of Twentieth Air Force. The 504th Bomb Group's aircraft engaged in B-29 Superfortress bombardment operations against Japan. Its aircraft were identified by a "E" inside a Circle painted on the tail.

The 504th Bombardment Group flew the last combat mission by the United States Army Air Forces of World War II, its last combat mission being on 15 August 1945.

The unit was established in early 1944 at Dalhart Army Air Field, Texas, being formed as a B-29 Superfortress Very Heavy bombardment Group. The unit was initially formed with four bomb squadrons (393d, 398th, 421st, and 507th ), being a mixture of both newly constituted and reassigned units. The 398th was formerly a III Bomber Command B-25 Mitchell medium bomber Operational Training Unit in the southeastern United States, being formed in 1942. It later became a B-26 Marauder Replacement Training Unit until being inactivated in October 1943.

Due to a shortage of B-29s, the group was initially equipped with former II Bomber Command B-17 Flying Fortresses previously used for training heavy bomber replacement personnel. The unit was then reassigned for advanced training and received B-29s at Fairmont Army Airfield, Nebraska during the late spring and summer of 1944.

In May shortages in aircraft and equipment led to the 507th Bomb Squadron being inactivated, with its personnel being consolidated into other group squadrons (the 507th would be reactivated a month later as part of the 333d Bombardment Group). In November, the 393d Bombardment Squadron was reassigned to the 509th Composite Group at Wendover Field, Utah, leaving the 504th to be a two squadron group. The 393d became the 509th's only operational B-29 squadron. The 393d would eventually become the only military unit in history to engage in Nuclear warfare, dropping Atomic Bombs on Hiroshima and Nagasaki, Japan, in August 1945.