J. Robert Oppenheimer was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is often credited as the "father of the atomic bomb" for his role in the Manhattan Project – the World War II undertaking that developed the first nuclear weapons. Oppenheimer was among those who observed the Trinity test in New Mexico, where the first atomic bomb was successfully detonated on July 16, 1945.