For many years until his death in 1988, William Sargant was a leading physician in psychological medicine. His research in World War II showed that with enough battle exposure, every soldier eventually shows the symptoms of battle fatigue, shell shock, or what we know now as post-traumatic stress disorder (PTSD). He went further to look at similar processes in religious conversion, spirit possession, brain-washing, political conversion, and the consultation of oracles in the ancient world. His basis was a Pavlovian theory, formulated more than seventy years earlier, but he extended Pavlov's model, sharing much with modern theories of PTSD.