Oppenheimer was the lead physicist on the "Manhattan Project." The project developed and built the first Atomic Bombs at Alamogordo, New Mexico during World War 2. The first was detonated at Trinity Site on the Alamogordo proving grounds. The second and third were dropped on Hiroshima and Nagasaki, Japan in August of 1945. Horrified by the destruction of these devices, Oppenheimer went on to oppose the building and use of nuclear weapons and was branded a subversive by the United States government during the McCarthy era in the 1950's.