J. Robert Oppenheimer

This 1946 photo of J. Robert Oppenheimer by Lisette Model hangs in the National Portrait Gallery in Washington, DC.

Beginning in 1942, the physicist J. Robert Oppenheimer oversaw the research and design of the atomic bomb for the Manhattan Project. His team at Los Alamos Laboratory tested the world's first nuclear weapon on July 16, 1945, and a few weeks later, the United States dropped atomic bombs over the Japanese cities of Hiroshima and Nagasaki. The devastation resulted in over 100,000 deaths and approximately 200,000 casualties. Oppenheimer subsequently served as chair of the General Advisory Committee of the Atomic Energy Commission, where he advised against developing a more powerful hydrogen bomb. 

In 1953, following accusations of disloyalty to the United States, Oppenheimer lost his security clearance and was prohibited from engaging in government-sponsored research. Oppenheimer had expressed leftist political sentiments in the 1930s and had not reported the full extent of his contact with a Soviet agent during the Manhattan Project, making him especially vulnerable to the anti-Communist witch hunts of the early 1950s. -- NPG