‘Mock Atomic Bombs’ Dropped Across Japan Near War’s End; Hundreds Killed in Missions to Test Trajectory, Boost Accuracy

“Mock atomic bombs” were dropped across Japan in July and August 1945, just before the end of World War II, to test their trajectory and thereby improve the accuracy of the devastating bombs that would ultimately be unleashed on Hiroshima and Nagasaki. Forty-nine such bombs — each weighing 4.5 tons, nearly the same weight as the “Fat Man” bomb released over Nagasaki — were dropped on 18 prefectures. They contained conventional explosives but had enough power to create craters upon impact.