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atomic bomb or A-bomb, weapon deriving its explosive force from the release of nuclear energy through the fission (splitting) of heavy atomic nuclei.The first atomic bomb was produced at the Los Alamos, N.Mex., laboratory and successfully tested on July 16, 1945.tomic bombs were subsequently developed by the USSR (1949; now Russia), Great Britain (1952), France (1960), and China (1964). A number of other nations, particularly India, Pakistan, Israel, and North Korea now have atomic bombs or the capability to produce them; South Africa formerly possessed a small arsenal.
The name Manhattan Project was the code word for the development of the atomic bomb. On July 16, 1945, the first atomic bomb was tested at the Trinity Site in New Mexico. The weapon was later used against the Japanese to end World War II.anhattan Project, the wartime effort to design and build the first nuclear weapons (atomic bombs). With the discovery of fission in 1939, it became clear to scientists that certain radioactive materials could be used to make a bomb of unprecented power.