He called the first atomic bomb "technically sweet," yet as he watched its brilliant light explode over the New Mexico desert in 1945 in advance of the black horrors of Hiroshima and Nagasaki, he also thought of the line from the Hindu epic The Bhagavad Gita: "I am become Death, the destroyer of worlds." Physicist J. Robert Oppenheimer, the scientific director of the Manhattan Project, the single most recognizable face of the atomic bomb, and...