After orgamnizing and training in the United states, the group served in the Pacific Ocean theater of World War II as part of Twentieth Air Force.

The group's Boeing B-29 Superfortress engaged in the strategic bombing campaign against Japan from January through August 1945, earning two Distinguished Unit Citations.

[2] In moved to Harvard Army Air Field, Nebraska on 1 April, where the group began training with Boeing B-17 Flying Fortresses on 1 July until B-29s became available.

[2] It began operations flying high altitude daylight missions, engaging in the strategic bombing campaign against Japan.

On 10 February, it flew a strike on the Nakajima Aircraft Company factory at Ota, for which it was awarded a Distinguished Unit Citation (DUC).

Low altitude night area attacks with incendiaries promised better results for XXI Bomber Command.