When the ashes had settled after World War II and the Allies convened an international war crimes trial in Nuremberg, a psychiatrist, Douglas Kelley, and a psychologist, Gustave Gilbert, tried to fathom the psychology of the Nazi leaders, using extensive psychiatric interviews, IQ tests, and Rorschach inkblot tests. Never before nor since has there been such a detailed study of governmental leaders who orchestrated mass killings. Before the war crimes...