In 1939, as the Nazis seemed intent on invading all of Europe, Enrico Fermi, Leo Szilard, and Edward Teller were among those who saw the destructive potential of a nuclear reaction. They realized that if a self-sustaining chain reaction were possible, this chain reaction would take place in an instant, releasing a huge amount of energy culminating in a tremendous explosion if uncontrolled. On the other hand, if the reaction could be controlled, the energy produced could drive generators that made electricity. Such controlled nuclear power could be a cheap and plentiful source of energy for all humankind.

Despite the great promise of atomic energy, the image that haunted the scientists was that of Hitler possessing an atomic bomb. This vision was especially frightening to Leo Szilard and Eugene Wigner, who had experienced firsthand the terrors of the Nazis when...