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 arms race megatons. On October 30, 1961, the Soviets detonated a hydrogen bomb with a yield of approximately 58 megatons. With both sides in the "cold war" having nuclear capability, an arms race developed, with the Soviet union attempting first to catch up and then to surpass the Americans. Strategic bombers were the primary delivery method at the beginning of the Cold War. Missiles had long been regarded the ideal platform for nuclear weapons, and were potentially a more effective delivery system than bombers. Starting in the 1950s, medium-range ballistic missiles and intermediate-range ballistic missiles ("IRBM"s) were developed for delivery of tactical