B-25 Bomber Loaded With 500-Pound Clusters of M54 Bombs

B-25 Bomber Loaded With 500-Pound Clusters of M54 Bombs leaving the flight deck of USS Hornet for the first American airstrike against the Japanese homeland, April 1942. 

The fact that the Air Forces almost never employed M54 s during the war made the production of steel-cased bombs, in one sense, a loss. On 

Four-pound magnesium bombs and other small incendiaries were not dropped individually, but in clusters which were held together by devices called adapters. 

The Ordnance Department began development of the first American adapter. The CWS inherited the item when it accepted responsibility for incendiary bombs. The device was made up of two end plates, two longitudinal bars, and four steel straps, and it held together thirty-four bombs. The adapter was designated as Model M5, the entire cluster of bombs as the AN-M6. A larger adapter, holding 128 bombs, was developed shortly afterward. This adapter was standardized as the M6, the cluster as the AN-M7. 

Aimable clusters were developed to improve the accuracy of high altitude bombing. Quick-opening clusters had been suitable for low or medium 

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