The Manhattan Engineer District, a secret U.S. government project begun in 1942 to develop an atomic bomb, was managed by Brigadier General Leslie Groves and undertaken by the U.S. Army Corps of Engineers. Under-taken at the urging of physicists Leo Szilard, Eugene Wigner, Edward Teller, Enrico Fermi, and Albert Einstein, the project responded to the threat of atomic weapon development by Nazi Germany. Ultimately, the U.S. effort brought together intelligence operatives, leading physicists, chemists, and engineers, as well as thousands of managers and workers at four major sites.

The best known of these sites, Los Alamos, in New Mexico, was the scientific and design headquarters of the project. Directed by the physicist J. Robert Oppenheimer, the Los Alamos site developed the theoretical knowledge behind the bomb and pieced together the designs for the two types of devices used on the Japanese cities of Hiroshima...