The science fiction stories of Cordwainer Smith (pen name of Paul Myron Anthony Linebarger (1913-1966), a US Army officer who specialized in military intelligence and psychological warfare during the Second World War and the Korean War) depict brainwashing to remove memories of traumatic events as a normal and benign part of future medical practice. Mind control remains an important theme in science fiction. A subgenre is "corporate mind control", in which a future society is run by one or more business corporations that dominate society using advertising and mass media to control the population's thoughts and feelings. Terry O'Brien commented: "Mind control is such a powerful image that if hypnotism did not exist, then something similar would have to have been invented: The plot device is too useful for any writer to ignore. The fear of mind control is equally as powerful an image."