Leo Szilard (1898-1964), a Hungarian-American physicist, was one of the first to realize that nuclear chain reactions could be used in bombs. Working at the University of Chicago with Enrico Fermi, he developed the first self-sustained nuclear reactor that operated on the fission of uranium. He helped convince Einstein to write a letter to President Franklin Roosevelt to establish a program to create the first atomic bomb, and went on to work with Enrico Fermi to create the first nuclear chain reaction. After World War II, he actively protested nuclear warfare and supported the use of nuclear energy only for peaceful purposes.
Cutler J. Cleveland (Lead Author);Peter Saundry (Topic Editor) "Szilard, Leo". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth September 10, 2008; Last revised Date September 10, 2008; Retrieved May 19, 2013 <http://www.eoearth.org/article/Szilard,_Leo>