Manhattan Project J . Robert Oppenheimer was the scientific director of the Manhattan Project , the top-secret World War II program which developed the world ' s first atomic bomb . Oppenheimer was an unusual personality : intensely brainy and ambitious and yet distinctly philosophical , with a facility for languages and an interest in Eastern religions and philosophy . In the 1930s he taught physics at both Caltech and the University of California at Berkeley , before being chosen to lead the Manhattan Project ' s team of scientists . The first atomic bomb was exploded on 16 July 1945 , and less than a month later President Harry S . Truman ordered two bombs dropped on Japan , ending World War II . After the war , Oppenheimer became head of the General Advisory Committee of the U . S . Atomic Energy Commission . As such , in 1949 he recommended against the development of the super-powerful hydrogen bomb , pitting him against fellow physicist and H-bomb proponent Edward Teller . n 1953 , during the era of intense anti-communism fomented by Senator Joseph McCarthy , Oppenheimer was accused of being a communist sympathizer , based on his support of various pro-communist and left-wing groups during the years before and during WWII . ncreasingly concerned about the potential danger to humanity arising from scientific discoveries , Oppenheimer joined with Albert Einstein , Bertrand Russell , Joseph Rotblat and other eminent scientists and academics to establish what would eventually become the World Academy of Art and Science in 1960 . Significantly , after his public humiliation , he did not sign the major open protests against nuclear weapons of the 1950s , including the Russell – Einstein Manifesto of 1955 .