The document summarizes the key events and people involved in the Manhattan Project, which was the US effort during World War II to develop the first atomic bombs. It describes the creation of the project under General Leslie Groves and its scientific director Robert Oppenheimer, the development of bombs using uranium-235 and plutonium, and the successful Trinity test in July 1945, which led to atomic bombs being dropped on Hiroshima and Nagasaki in August, ending the war. After the war, the Soviet Union also developed atomic weapons, beginning the Cold War era of nuclear deterrence between the two superpowers.