Nuclear fission Mexico, which was the scientific hub for research on bomb development and design. Other sites, notably the Berkeley Radiation Laboratory and the Metallurgical Laboratory at the University of Chicago, played important contributing roles. Overall scientific direction of the project was managed by the physicist J. Robert Oppenheimer. In July 1945, the first atomic explosive device, dubbed "Trinity", was detonated in the New Mexico desert. It was fueled by plutonium created at Hanford. In August 1945, two more atomic devices – "Little Boy", a uranium-235 bomb, and "Fat Man", a plutonium bomb – were used against the Japanese cities of Hiroshima
Nuclear testing at Bikini Atoll series was Castle Bravo, a new design utilizing a dry fuel thermonuclear hydrogen bomb. It was detonated at dawn on March 1, 1954. The 15 megaton (Mt) nuclear explosion far exceeded the expected yield of 4 to 8 Mt (6 Mt predicted), and was about 1,000 times more powerful than each of the atomic bombs dropped on Hiroshima and Nagasaki during World War II. The nuclear weapon was the most powerful device ever detonated by the United States (and just under one-third the energy of the Tsar Bomba, the largest ever tested). The scientists and military authorities were shocked by