The Manhattan Project was started by President Roosevelt in 1942 to ensure that the U.S. beat the Germans in developing a nuclear bomb. Whom did Roosevelt appoint as scientific head the Manhattan Project?

Leslie R. Groves, however, was the military head of the project and the overall supremo, while Robert Oppenheimer was the scientific director. The world's first atomic bomb was exploded in the New Mexico desert on July 16, 1945.