Thanks to Wikipedia for the following info: The 509th Composite Group (509 CG) was a unit of the United States Army Air Forces created during World War II and tasked with the operational deployment of nuclear weapons. It conducted the atomic bombings of Hiroshima and Nagasaki, Japan, in August 1945.
The group was activated on 17 December 1944 at Wendover Army Air Field, Utah. It was commanded by Lieutenant Colonel Paul W. Tibbets. Because it contained flying squadrons equipped with Boeing B-29 Superfortress bombers and C-47 Skytrain and C-54 Skymaster transport aircraft, the group was designated as a "composite" rather than a "bombardment" formation. It operated Silverplate B-29s, which were specially configured to enable them to carry nuclear weapons.
The 509th Composite Group began deploying to North Field on Tinian, Northern Mariana Islands, in May 1945. In addition to the two nuclear bombing raids, it carried out 15 practice missions against Japanese-held islands, and 12 combat missions against targets in Japan dropping high-explosive pumpkin bombs.
In the postwar era, the 509th Composite Group was one of the original ten bombardment groups assigned to Strategic Air Command on 21 March 1946 and the only one equipped with Silverplate B-29 Superfortress aircraft capable of delivering atomic bombs. It was standardized as a bombardment group and re-designated the 509th Bombardment Group, Very Heavy, on 10 July 1946. After each atomic mission the group conducted other combat operations, making a series of pumpkin bomb attacks on 8 and 14 August. Six B-29s visually attacked targets at Yokkaichi, Uwajima, Tsuruga, and Tokushima on 8 August, bombing two primary and three secondary targets with five bombs. Seven aircraft visually attacked Koroma and Nagoya on 14 August.Some Punkins (Crew B-7, Price) is believed to have dropped the last bombs by the Twentieth Air Force in World War II. After the announcement of the Japanese surrender, the 509th Composite Group flew three further training missions involving 31 sorties on 18, 20 and 22 August, then stood down from operations. The group made a total of 210 operational sorties from 30 June to 22 August, aborted four additional flights, and had only a single aircraft fail to take off. Altogether, 140 sorties involved the dropping of live ordnance. Some 60 flights were credited as combat missions: 49 pumpkin bomb and 11 atomic bomb sorties.
Three B-29s (Full House, Straight Flush, and Top Secret) flew six combat missions each. Crews A-1 (Taylor) and C-11 (Eatherly) flew the most combat missions, six (including one atomic mission) each, while six other crews each flew five. Only the late arrivals (A-2 [Costello] and C-12 [Zahn]) did not participate in any combat missions, although Costello's B-29 was used by another crew for weather reconnaissance of Nagasaki on the second mission. Including training and test flights, crews B-8 (McKnight) and C-13 (Bock) flew the most missions, with 20 total (5 combat). Crew B-7 (Price) is the only crew to fly all of its missions (18 total, 5 combat) in its normally assigned aircraft, Some Punkins.
The 509th Composite Group returned to the United States on 6 November 1945, and was stationed at Roswell Army Airfield, New Mexico. Colonel William H. Blanchard replaced Tibbets as group commander on 22 January 1946, and also became the first commander of the 509th Bombardment Wing. It was one of the original ten bombardment groups assigned to Strategic Air Command when it was formed on 21 March 1946. The 715th and 830th Bombardment Squadrons were assigned to the 509th on 6 May 1946, and the group was redesignated the 509th Bombardment Group, Very Heavy on 10 July. The 320th Troop Carrier Squadron was inactivated on 19 August. At Roswell, the 509th became the nuclear strike and deterrence core of the Strategic Air Command, and was the only unit capable of delivery of nuclear weapons until June 1948, when B-50 Superfortresses were initially deployed. The 509th itself converted to the B-50 in 1950, and transferred its Silverplate B-29s to the squadrons of the 97th Bombardment Wing at Biggs Air Force Base, Texas.