'Robert Oppenheimer,' by Ray Monk Oppenheimer, as the scientific director of the project, played perhaps the decisive role in delivering a working atomic weapon, which President Harry Truman ordered to be used, with devastating effects, against two Japanese cities. Overruled by his president, Oppenheimer then watched as his archrival, fellow physicist Edward Teller, pressed ahead and, with the help of others, built the weapon that by the end of the 1950s would sit at the heart of an American "doomsday machine," a network of bombers and missiles that, if exhausted, would bring about the "mutual assured destruction" not only of the Soviet Union, America's Cold War enemy, but also perhaps the entire planet. In this, he was spectacularly unsuccessful, so much so that his influential opponents, notably Teller, managed to engineer his humiliation in the form of his expulsion from the "classified" inner circle of wise men and super-scientists that for 50 years defined U.S.