504th Bombardment Group

The 504th Bombardment Group was a World War II combat organization of the United States Army Air Forces. Constituted as a very-heavy bombardment group on 18 February 1944 and activated at Dalhart Army Air Field, Texas, on 11 March 1944, it was formed to operate the Boeing B-29 Superfortress against Japan. Its original structure included the 393d, 398th, 421st, and 507th Bombardment Squadrons, although wartime reorganizations soon changed the group’s composition. The group initially faced the broader B-29 program’s equipment shortage. Rather than immediately receiving Superfortresses, it used Boeing B-17 Flying Fortresses for training. It moved to Fairmont Army Air Field, Nebraska, where it undertook advanced preparation and began receiving B-29s during the late spring and summer of 1944. In May, the Army Air Forces reduced the standard size of many B-29 groups from four squadrons to three, resulting in the inactivation and redistribution of the 507th Bombardment Squadron. Later that year, the 393d Bombardment Squadron was transferred to the 509th Composite Group, leaving the 504th primarily as a two-squadron organization. The 393d subsequently participated in the atomic bombing missions against Hiroshima and Nagasaki as part of its new organization. The 504th deployed to the Pacific late in 1944. It was assigned to the 313th Bombardment Wing of XXI Bomber Command and based at North Field on Tinian in the Mariana Islands. Combat operations began in January 1945 with attacks on Japanese airfields and installations in the Central Pacific, including targets on Maug, Iwo Jima, and in the Truk Islands. In early February, the group conducted its first mission against the Japanese home islands, striking the industrial area of Kobe. During the first part of its combat deployment, the group performed high-altitude daylight attacks against strategically important targets such as aircraft factories, chemical facilities, ports, and arsenals. Beginning in March 1945, it also participated in low-altitude nighttime incendiary raids against urban and industrial areas. Its missions expanded to include aerial mining, particularly against Japanese shipping routes in Korea, the Shimonoseki Strait, and ports of the Inland Sea. During April and May, the group attacked airfields used by Japanese forces conducting kamikaze operations during the fighting for Okinawa. The group received two Distinguished Unit Citations. The first recognized its attack on the industrial center of Yokohama in late May 1945. The second covered its mining operations against Japanese maritime routes during July and August. In June, the 680th Bombardment Squadron was attached to help restore the group to a three-squadron combat strength. The 504th continued strategic bombing, incendiary attacks, and related operations until Japan’s capitulation. Its final combat mission on 15 August 1945 is regarded as the last combat mission flown by the United States Army Air Forces during World War II. After V-J Day, the group performed non-combat duties, including dropping supplies to Allied prisoners of war, conducting show-of-force flights, and surveying bomb damage over Japan. It was progressively reduced during the postwar demobilization known as the Sunset Project. Many aircraft were sent to reclamation or storage, and the remaining personnel were returned to the United States for discharge. In March 1946, the largely depleted organization was transferred to Clark Field in the Philippines and assigned to the Thirteenth Air Force. Its remaining personnel and aircraft were consolidated into other units, and the 504th Bombardment Group was inactivated on 15 June 1946.

The 504th Bombardment Group was created during the rapid expansion of the United States Army Air Forces’ very-heavy bombardment capability in World War II. It was constituted on 18 February 1944 and activated on 11 March at Dalhart Army Air Field, Texas. The group was organized around four bombardment squadrons: the 393d, 398th, 421st, and 507th. These components had different institutional backgrounds. In particular, the 398th had previously served in medium-bomber training roles involving the North American B-25 Mitchell and Martin B-26 Marauder. The new group’s training period was affected by the limited availability of B-29 aircraft. It initially used B-17 Flying Fortresses that had previously supported heavy-bomber replacement training. On 12 March 1944, it moved to Fairmont Army Air Field, Nebraska, for advanced preparation. B-29s became available there during the late spring and summer, allowing crews and ground personnel to transition to the aircraft that would define the group’s operational career. The Army Air Forces reorganized B-29 groups in May 1944, generally reducing them from four squadrons to three. The 507th Bombardment Squadron was consequently inactivated within the group and its personnel were redistributed. On 5 November, the 504th left the Second Air Force training structure. The 393d Bombardment Squadron was transferred on 25 November to the 509th Composite Group at Wendover Field, Utah. This reassignment left the 504th with the 398th and 421st Bombardment Squadrons as its principal operational components. The 393d later became the 509th group’s operational B-29 squadron for the atomic missions against Hiroshima and Nagasaki. The 504th reached the Pacific in late 1944 and was assigned to the 313th Bombardment Wing. Its overseas station was North Field on Tinian in the Mariana Islands, one of the principal bases for the strategic air campaign against Japan. The group began combat operations in January 1945 against Japanese airfields and installations in the Central Pacific. Its first attack on the Japanese home islands followed in early February, when it bombed industrial targets at Kobe. The group initially conducted daylight, high-altitude attacks against selected strategic objectives, including factories connected with aircraft production, chemical plants, ports, and arsenals. As Army Air Forces tactics evolved in the spring of 1945, the 504th also flew nighttime, low-level incendiary raids against densely built-up urban and industrial areas. It began mining operations late in March, placing mines in waters used by Japanese shipping. These missions extended to Korean shipping lanes, the Shimonoseki Strait, and harbors of the Inland Sea. In April and May, the group attacked Japanese airfields associated with kamikaze operations during the Okinawa campaign. The group’s performance earned it two Distinguished Unit Citations. One recognized its late-May attack on Yokohama’s industrial center. The other recognized the mining campaign conducted during July and August. On 15 June 1945, the 680th Bombardment Squadron was attached to increase operational strength, and it was later assigned to the group. The 504th continued bombing and mining missions through the final phase of the Pacific war. Its mission on 15 August 1945, the day Japan accepted the Allied surrender terms, is identified as the last combat mission flown by the United States Army Air Forces during World War II. Following Japan’s capitulation, the group shifted to humanitarian and assessment duties. It dropped supplies to Allied prisoners of war, conducted show-of-force flights, and photographed or otherwise evaluated the effects of bombardment over Japan. Demobilization rapidly reduced its aircraft and personnel under the Sunset Project. Some aircraft were sent to reclamation facilities on Tinian, while others were returned to the United States for storage. By the end of 1945, the group had fewer than or approximately thirty aircraft remaining, and many veterans returned home for discharge. In March 1946, the largely nominal organization moved to Clark Field on Luzon and came under the Thirteenth Air Force. Its remaining assets were absorbed by other units. The 504th Bombardment Group was formally inactivated on 15 June 1946, ending its existence as an active Army Air Forces organization.

• 1946

  Inactivation

  [1]504th Bombardment Groupen.wikipedia.org

  After reassignment to Clark Field and consolidation of its remaining assets, the group was inactivated on 15 June.

• 1945

  Beginning of Pacific combat operations

  [1]504th Bombardment Groupen.wikipedia.org

  The group began combat missions against Japanese installations in January and attacked Kobe during its first mission against the Japanese home islands in February.

• 1945

  Distinguished Unit Citation for Yokohama mission

  [1]504th Bombardment Groupen.wikipedia.org

  The group received a Distinguished Unit Citation for its attack on Yokohama’s industrial center in late May.

• 1945

  Final USAAF combat mission

  [1]504th Bombardment Groupen.wikipedia.org

  On 15 August, the group flew what is identified as the final combat mission of the United States Army Air Forces in World War II.

• 1944

  Constitution as a very-heavy bombardment group

  [1]504th Bombardment Groupen.wikipedia.org

  The 504th Bombardment Group was constituted on 18 February to operate as a B-29 very-heavy bombardment organization.

• 1944

  Activation and initial training

  [1]504th Bombardment Groupen.wikipedia.org

  The group was activated at Dalhart Army Air Field, Texas, on 11 March and began training with B-17 aircraft before transitioning to B-29s.

• 1944

  Transfer of the 393d Bombardment Squadron

  [1]504th Bombardment Groupen.wikipedia.org

  The 393d Bombardment Squadron was reassigned to the 509th Composite Group in November, leaving the 504th as a primarily two-squadron group.

• 1944

  Deployment to Tinian

  [1]504th Bombardment Groupen.wikipedia.org

  The group deployed to North Field, Tinian, in the Mariana Islands, under the 313th Bombardment Wing.

A wartime United States Army Air Forces B-29 bombardment group specializing in long-range strategic bombing, incendiary attacks, and aerial mining in the Central Pacific.

• Training aircraft · 1944

  Boeing B-17 Flying Fortress

  The group used B-17s during its initial training period because B-29 Superfortresses were in short supply. These aircraft supported preparation for heavy-bomber operations but were not the group’s principal combat aircraft.

• Very-heavy bomber · 1944

  Boeing B-29 Superfortress

  The B-29 was the 504th Bombardment Group’s primary operational aircraft from 1944 through 1946. From Tinian, the group used the type for high-altitude strategic bombing, nighttime incendiary attacks, aerial mining, attacks on airfields, postwar supply drops, and damage-assessment flights.

• 1945Central Pacific and Japanese home-island bombing campaign

  Central Pacific and Japan

  From Tinian, the group attacked Japanese airfields, industrial facilities, ports, arsenals, and other installations. It combined daylight high-altitude bombing with later nighttime incendiary raids.

  Outcome. Operations continued until Japan’s capitulation in August 1945. The group received a Distinguished Unit Citation for its Yokohama operation.

  Source
• 1945Okinawa support operations

  Japan and the Ryukyu area

  During April and May, the group attacked Japanese airfields used to launch kamikaze aircraft against Allied forces involved in the Okinawa campaign.

  Outcome. The operations supported the wider Allied campaign for Okinawa and continued the group’s strategic and tactical pressure on Japanese air power.

  Source
• 1945Maritime mining campaign

  Korean waters · the Shimonoseki Strait · and the Inland Sea

  Beginning late in March, the group laid aerial mines against Japanese shipping routes and harbor approaches.

  Outcome. The campaign was recognized by a second Distinguished Unit Citation covering mining operations conducted during July and August.

  Source

• 1945

  Expansion into nighttime incendiary raids and aerial miningStrategy

  Background

  The group’s initial missions emphasized high-altitude daylight attacks against selected strategic targets.

  Action taken

  From March, it added low-altitude nighttime incendiary operations and maritime mining missions to its bombing program.

  Aftermath

  The group received unit citations for major bombing and mining operations and continued these roles until Japan’s surrender.

  Source

• 1944

  Transition from B-17 training to B-29 operationsStrategy

  Background

  The group was created for very-heavy bombardment, but B-29 availability was initially insufficient.

  Action taken

  It used B-17 aircraft for initial training and later transitioned to B-29 Superfortresses at Fairmont Army Air Field.

  Aftermath

  The transition enabled the group’s deployment to the Pacific as a B-29 combat organization.

  Source

1. 1504th Bombardment Groupen.wikipedia.org