THE UNITED STATES NUCLEAR WEAPON PROGRAM: A SUMMARY HISTORY Introduction The origins of the United States' nuclear weapon program can be traced to the discovery of fission in 1939. After scientists discovered ’ that an atom of uranium could be split, they also realized that fission could release huge amounts of energy. If a fission bamb could be developed, weapons of tremendous explosive power could be producedé. weapons potential of fission was as The apparent to American nucl physicists as to their counterparts in Nazi Gemmany .+ Because German scientists had discovered fission, Hitler seemed to have a significant head start on the road to a weapon which could terrorize Eurcse and perhaps even the United States. American scientists organized ther selves into research teams in an urgent effort to develop an atomic bamb before Germany. their efforts. Hitler's attack on Poland and the fall of France Sueled When the United States entered the war in December1941, the atemic effort already had became a large project involving teams of researchers directed by scientist-administrators Vannevar Bush and James B. Conant. Thereafter the Manhattan Engineer District under General Leslie Groves built the plants and laboratories required to produce a bomb. At Oak Ridge, Tennessee, Groves' engineers erected a huge gaseous diffusicn plant to produce enriched uranium. At Hanford, Washington they built three reactors to produce the recently discovered fissionable element plutonium. Finally at Los Alamos Groves created a weapon laberatcry under the direction of J. Robert Oppenheimer to design atomic barbs. Oppenheimer and his colleagues were certain that a "gum" bom usins 1