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, 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 redesignated the 509th Bombardment Group, Very Heavy, on 10 July 1946.
History Organization, training, and security
The 509th Composite Group was constituted on 9 December 1944, and activated on 17 December 1944, at Wendover Army Air Field, Utah. It was commanded by Lieutenant Colonel Paul W. Tibbets, who received promotion to full colonel in January 1945. It was initially assumed that the group would divide in two, with half going to Europe and half to the Pacific. In the first week of September Tibbets was assigned to organize a combat group to develop the means of delivering an atomic weapon by airplane against targets in Germany and Japan, then command it in combat. Because the organization developed by Tibbets was self-sustained, with flying squadrons of both Boeing B-29 Superfortress bombers and transport aircraft, the group was designated as a "composite" rather than a "bombardment" unit.
On 8 September, working with Major General Leslie R. Groves, Jr.'s Manhattan Project, Tibbets selected Wendover for his training base over Great Bend Army Air Field, Kansas, and Mountain Home Army Airfield, Idaho, because of its remoteness. On 14 September 1944, the 393d Bombardment Squadron arrived at Wendover from its former base at Fairmont Army Air Base, Nebraska, where it had been in operational training (OTU) with the 504th Bombardment Group since 12 March. When its parent group deployed to the Marianas in early November 1944, the squadron was assigned directly to the Second Air Force until creation of the 509th Composite Group. Originally consisting of twenty-one crews, fifteen were selected to continue training, and were organized into three flights of five crews, lettered A, B, and C. The 393d Bombardment Squadron was commanded by Lieutenant Colonel Thomas J. Classen, who like Tibbets had combat experience in heavy bombers, commanding a Boeing B-17 Flying Fortress with the 11th Bombardment Group.
The 393d Bombardment Squadron conducted ground school training only until delivery of three modified Silverplate airplanes in mid-October 1944 allowed resumption of flight training. These aircraft had extensive bomb bay modifications and a "weaponeer" station installed. Initial training operations identified numerous other modifications necessary to the mission, particularly in reducing the overall weight of the airplane to offset the heavy loads it would be required to carry. Five more Silverplates were delivered in November and six in December, giving the group 14 for its training operations. In January and February 1945, 10 of the 15 crews under the command of the Group S-3 (operations officer) were assigned temporary duty at Batista Field, San Antonio de los Baños, Cuba, where they trained in long-range over-water navigation.
The 320th Troop Carrier Squadron, the other flying unit of the 509th, came into being because of the highly secret work of the group. The organization that was to become the 509th required its own transports for the movement of both personnel and materiel, resulting in creation of an ad hoc unit nicknamed "The Green Hornet Line". Crews for this unit were acquired from the five 393d crews not selected to continue B-29 training. All those qualified for positions with the 320th chose to remain with the 509th rather than be assigned to a replacement pool of the Second Air Force. They began using C-46 Commando and C-47 Skytrains already at Wendover, and in November 1944 acquired three C-54 Skymasters. The 320th Troop Carrier Squadron originally consisted of three C-54 and four C-47 aircraft. In April 1945 the C-47s were transferred to the 216th Army Air Forces Base Unit and two additional C-54s acquired. The 320th Troop Carrier Squadron was constituted and activated on the same dates as the group.
Other support units were activated at Wendover from personnel already present and working with Project Alberta or in the 216th Army Air Forces Base Unit, both affiliated with the Manhattan project. Project Alberta was the part of the Manhattan Project at Site Y in Los Alamos, New Mexico, responsible for the preparation and delivery of the nuclear weapons. It was commanded by U.S. Navy Captain William S. Parsons, who would accompany the Hiroshima mission as weaponeer. On 6 March 1945, concurrent with the activation of Project Alberta, the 1st Ordnance Squadron, Special (Aviation) was activated at Wendover, again using Army Air Forces personnel on hand or already at Los Alamos. Its purpose was to provide "skilled machinists, welders and munitions workers" and special equipment to the group to enable it to assemble atomic weapons at its operating base, thereby allowing the weapons to be transported more safely in their component parts. A rigorous candidate selection process was used to recruit personnel, reportedly with an 80% "washout" rate. Not until May 1945 did the 509th Composite Group reach full strength.
The 390th Air Service Group was created as the command echelon for the 603rd Air Engineering Squadron, the 1027th Air Material Squadron, and its own Headquarters and Base Services Squadron, but when these units became independent operationally, it acted as the basic support unit for the entire 509th Composite Group in providing quarters, rations, medical care, postal service and other functions. The 603rd Air Engineering Squadron was unique in that it provided depot-level B-29 maintenance in the field, obviating the necessity of sending aircraft back to the United States for major repairs. On Tinian the 603rd Air Engineering Squadron was assigned to the 313th Bombardment Wing's "C" and "D" Service Centers, where it performed provided depot-level ("third echelon") maintenance for the entire 313th Bombardment Wing when it was not engaged in 509th activities. The 393d Bombardment Squadron's maintenance section was re-organized as a "combat line maintenance" section (also called PLM, or "production line maintenance," a technique developed by the Air Transport Command in India for "Hump" aircraft) to maximize use of personnel for first and second echelon maintenance.
Overseas movement With the addition of the 1st Ordnance Squadron to its roster, the 509th Composite Group had an authorized strength of 225 officers and 1,542 enlisted men, almost all of whom deployed to Tinian. The 320th Troop Carrier Squadron kept its base of operations at Wendover. In addition to its authorized strength, the 509th had attached to it on Tinian 51 civilian and military personnel of Project Alberta, and two representatives from Washington, D.C., the deputy director of the Manhattan Project, Brigadier General Thomas Farrell, and Rear Admiral William R. Purnell of the Military Policy Committee.
The 509th's personnel and equipment were subject to a high level of security. En route to Tinian on 4 June 1945, the B-29 that became The Great Artiste made an intermediate stop at Mather Field, near Sacramento, California. The commanding general of the base allegedly attempted to enter the aircraft to inspect it and was warned by a plane guard who aimed his carbine at the general's chest that he could not do so. A similar incident occurred to a Project Alberta courier, 2nd Lieutenant William A. King. King was escorting the plutonium core of the Fat Man implosion bomb to Tinian, strapped to the floor of one of the 509th's C-54s. On 26 July 1945 it made a refueling stop at Hickam Field, Hawaii. The commander of a combat unit returning to the United States learned that the Skymaster had only one passenger and attempted to enter the C-54 to requisition it as transport for his men. He was prevented from doing so by King, who aimed a .45 caliber automatic pistol at the colonel.
The 509th transferred four of its 14 training Silverplate B-29s to the 216th AAF Base Unit in February 1945. In April the third modification increment of Silverplates, which would be their combat aircraft, began coming off the Martin-Omaha assembly line. These "fly-away" aircraft were equipped with fuel-injected engines, Curtiss Electric reversible-pitch propellers, pneumatic actuators for rapid opening and closing of bomb bay doors and other improvements. The remaining 17 Silverplate B-29s were placed in storage. Each bombardier completed at least 50 practice drops of inert pumpkin bombs before Tibbets declared his group combat-ready.
The ground support echelon of the 509th Composite Group, consisting of 44 officers and 815 enlisted men commanded by Major George W. Westcott of the Headquarters Squadron, received movement orders and moved by rail on 26 April 1945 to its port of embarkation at Seattle, Washington. On 6 May the support elements sailed on the SS Cape Victory for the Marianas, while group materiel was shipped on the SS Emile Berliner. The Cape Victory made brief port calls at Honolulu and Eniwetok but the passengers were not permitted to leave the dock area. An advance party of the air echelon, consisting of 29 officers and 61 enlisted men commanded by Group Intelligence Officer (S-2) Lieutenant Colonel Hazen Payette, flew by C-54 to North Field, Tinian, between 15 and 22 May. It was joined by the ground echelon on 29 May 1945, marking the group's official change of station. Project Alberta's "Destination Team" also sent most of its members to Tinian to supervise the assembly, loading, and dropping of the bombs under the administrative title of 1st Technical Services Detachment, Miscellaneous War Department Group.
Equipment and crews
The air echelon consisted of the members of the 393d Bombardment Squadron. The 320th Troop Carrier Squadron remained at Wendover. It began deploying from Wendover 4 June 1945, with the first B-29 arriving at North Field on 11 June. The group was assigned to the 313th Bombardment Wing, whose four groups had been flying missions against Japan since mid-February, but for security reasons their permanent base area was near the runways on the island's north tip, several miles away from the main installations in the center of Tinian. The 509th, after spending most of June in an area previously occupied by the Seabees of the 18th Naval Construction Battalion, took over the 13th Naval Construction Battalion Area just west of North Field's Runway D, a self-contained base with 89 Quonset huts, a huge storage warehouse, a consolidated mess hall, chapel, administrative area, theater, and other amenities.