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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 first bomb was exploded over Hiroshima on August 6, 1945, and a second was dropped on Nagasaki on August 8. The Japanese quickly surrendered. Although other nations have developed atomic weapons and nuclear technology since 1945, Truman remains the only world leader to have ever used an atomic bomb against an enemy.resident Harry Truman learns the full details of the Manhattan Project, in which scientists are attempting to create the first atomic bomb, on this day in 1945.