This book views nine physicists who were crucial to the development of the first nuclear weapons as a group rather than as distinct individuals. The initial chapters address their efforts to build the atomic bomb and to use it to end World War II. Later chapters deal with how those scientists came to a realization of the bomb's impact on their lives and on society in general and struggled to come to terms with the creation of nuclear weapons. The nine physicists selected are Hans Bethe, Niels Bohr, Arthur Compton, Enrico Fermi, Ernest Lawrence, J. Robert Oppenheimer, I. I. Rabi, Leo Szilard, and Edward Teller. The author is a historian.