The concept for the high-explosive pumpkin bomb was originated in December 1944 by United States Navy Captain William S. Parsons, the head of the Ordnance Division at Manhattan Project's Los Alamos Laboratory, and United States Army Air Forces Lieutenant Colonel Paul W. Tibbets, commander of the 509th Composite Group.

[1] The name "pumpkin bomb" originated with Parsons and Dr. Charles C. Lauritsen of the California Institute of Technology, who managed the development team.

[6] The test program was initiated on 13 August 1943 at the Naval Proving Ground in Dahlgren, Virginia, where a scale model of the Fat Man plutonium bomb was developed.

[1] All of the inert versions went from the manufacturers directly to Wendover Army Air Field, Utah, by rail, where they were used by the 216th Base Unit in flight testing of the bomb.

[1] The bombs intended as live ordnance were shipped to the Naval Ammunition Depot, McAlester, Oklahoma, for filling with explosives.

The Composition B was poured as a slurry, solidified in a drying facility for 36 hours, sealed, and shipped by railroad to the Port Chicago Naval Magazine, California, for shipment by sea to Tinian.

[1] Combat missions were flown by the 509th Composite Group on 20, 23, 26 and 29 July and 8 and 14 August 1945, using the bombs against individual targets in Japanese cities.