509th Composite Group

The 509th Composite Group, a special unit of the US Army Air Force, was assembled in late 1944 at Wendover Field, Utah under Col. Paul W. Tibbets, Jr. Their sole and singular mission was to train for the delivery of the atomic bomb, then in final development in the Manhattan Project.

By the end of May 1945, the 509th was relocated to Tinian in the Mariana Islands, within B-29 range of Japan. In August they delivered the first atomic bombs in missions to Hiroshima and Nagasaki, Japan.

The 509th Composite Group's success ended the war with Japan, brought World War II to a close, and doubtless saved many lives.

HQ 509th Composite Group,  Tinian, 1945
HQ 509th Composite Group, Tinian, 1945
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History of the 509th Composite Group

On 17 December 1944, by direction of the War Department and the Second Air Force, the 509th Composite Group was established at Wendover Field, Utah, a location chosen for its isolation required by the secrecy of the 509th's mission.

The 509th immediately began training in fifteen specially-modified Boeing B-29 Superfortress bombers assigned to the group for "special weapons" delivery. At that time, the B-29 was the largest, longest range bomber in the U.S. arsenal. The 509th was the first USAAF bombardment group to be organized, equipped, and trained for atomic warfare. The 509th's training was top secret and the existence of the group was not released until after the war.

The Commander of the 509th Composite Group was Col. Paul W. Tibbets, Jr. (later Gen. Tibbets), selected in July 1944 for his outstanding service and abilities. The single tactical squadron of the 509th, the 393rd Bombardment Squadron (Very Heavy), was commanded by Major Charles W. Sweeney.

Because the 509th had a unique mission, existing organization and procedures in the Army Air Forces did not fit. Special orders and modifications to T/Os were made and entire sub-groups were transferred to the 509th to support their requirements. A number of men with specialty skills, such as welders and machinists, were transferred into the 509th, picked from throughout the Air Corps and even ground forces for this top priority mission. Exacting requirements and selection criteria caused 80% of those interviewed for work with the 509th to be rejected, only 20% accepted for duty. At peak, the 509th had a total strength of 225 officers and 1542 enlisted men.

From Wendover to Forward Base Tinian

In early 1945, the 509th conducted intensive training in the operation and maintenance of the B-29s and the conduct of radar bombing missions from 20,000 to 30,000 feet, operating from Wendover, Utah but also including training in Cuba and elsewhere. The main ground echelon of the 509th completed training and departed Wendover on 26 April 1945, travelling by rail to Seattle, then by ship via Hawaii and Eniwetok, arriving at Tinian Island on 29 May 1945. The aircraft flew from Wendover to Tinian, via West Coast airfields, Hawaii, and other Pacific island bases during the last two weeks of May. Most of the 509th were at their base on Tinian Island by mid-June 1945, but individuals and small groups, plus specialty equipment continued to arrive though July and early August. 11 June 1945 was designated as the day the 509th officially took up residence at the 18th N.C.B. Area on Tinian, including the arrival of the first B-29s from Wendover. In July they moved again, to the 13th N.C.B. Area, where they took over 89 quonset huts, a mess hall, warehouse and other buildings, operating from North Field.

Preparations for the Atomic Mission

Loading atomic bomb Enola Gay
B-29 "Enola Gay" in process of loading the atomic bomb, in pit, center left. The plane was backed up over the pit and the bomb was then lifted straight up into the bomb bay by a hoist.

Tinian was in the central Pacific Marianas, in sight of Saipan three miles away, only 1,450 miles from Tokyo. Since its capture by the Marines during July-August 1944, it had been turned into the largest airfield in the world with over 500 B-29s operating from there on daily missions. The 509th, with its aircraft identified by a distinctive insignia of a circled black arrow, ran more combat training and practice flights from the island during July and early August 1945, including four bombings of Japan itself (staring on 20 July) with "pumpkin" bombs simulating the forthcoming atomic weapon. The most crucial finding of the test runs was that weather over the target was the crucial factor determining mission success or failure.

On 25 July 1945, the U.S.S. Indianapolis delivered the components of the atomic bomb to the 509th on Tinian. In the two weeks prior to the atomic bomb missions, special briefings were held for the selected crews. The missions to bomb Hiroshima and Nagasaki were on 6 August 1945 and 9 August 1945, respectively.

The group continued to exist after World War II as the USAF 509th Bomb Wing.

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