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 weapons of the United States 1 November 1945 and with Japan not surrendering, President Harry S. Truman ordered the atomic raids on Japan. On 6 August 1945, the U.S. detonated a uranium-gun design bomb, Little Boy, over the Japanese city of Hiroshima with an energy of about 15 kilotons of TNT, killing approximately 70,000 people, among them 20,000 Japanese combatants and 20,000 Korean slave laborers, and destroying nearly 50,000 buildings (including the 2nd General Army and Fifth Division headquarters). Three days later, on 9 August, the U.S. attacked Nagasaki using a plutonium implosion-design bomb, Fat Man, with the explosion equivalent to about 20 kilotons of