Historian Daniel Kevles called World War II the “Physicist’s War.” World War II represented the greatest expenditure on a physics program in history. It developed two main technologies: radar and the atomic bomb. The splitting of the atom opened a tremendous new possibility to harness energy. In 1937, German scientists Otto Hahn and Fritz Strassman had discovered if you bombard a uranium atom with neutrons, you could split the nucleus and in the process release a great deal of energy. This began the race for atomic weaponry.
In 1941, several European immigrant scientists’, many of whom were fleeing the Nazi regime and were concerned about the possibility of Hitler controlling such a powerful weapon, convinced Albert Einstein to write President Franklin Roosevelt using his considerable clout to plead for the development of a nuclear weapon. Roosevelt agreed and created the civilian run Advisory Committee on Uranium. In 1942, dissatisfied with the progress of the Committee, the development of nuclear weaponry was handed over to the military under the direction of General Leslie Groves. Groves renamed the project the innocuous title of “The Manhattan Project.” From the beginning Groves wanted Oppenheimer to be the project leader, despite his somewhat controversial political history. When asked why after the war, Groves said:
"He's a genius. A real genius... Why, Oppenheimer knows about everything. He can talk to you about anything you bring up. Well, not exactly. I guess there are a few things he doesn't know about. He doesn't know anything about sports."
Groves and Oppenheimer jointly decided to move the development process out of the basements of the universities and to a central site in the desert near Los Alamos, New Mexico. There Oppenheimer began supervision of over 3000 of the best physicists of the time in the development of the atomic bomb.
On July 16, 1945, the first atomic bomb was set off at the Trinity Site. The scientists involved cheered and congratulated each other as their creation was proven to be successful. Oppenheimer was said to have been much more subdued. He is said to have uttered a now famous quotation from the Hindu Bhagavad-Gita, “I am become death: the destroyer of worlds.” Oppenheimer’s conscience and his past political affiliations would come back to haunt him.