War and killing have accompanied people throughout history. Moreover, with the development of civilisation, hostilities become more intense, and battlefields often turn into places of mass hecatombs. So can we define a man as a born mass murderer? Former U.S. Army Ranger and West Point psychology professor Lieutenant Colonel Dave Grossman denies this idea. Offering a systematic study of the nature of killing, he argues that most of us avoid killing, and that the increasing number of casualties in modern warfare is more likely a consequence of the development of training methods and technologies that make military personnel more efficient and destructive. But there is another side to this intensification: overcoming the instinctive hatred of killing through modern methods of military training has led to an increase in combat stress, and the rates of casualties from psychological trauma have become comparable to those from gunshot wounds. Moreover, modern media products, in which producers imitate military training methods, contribute to the growth of violence in society. All of this obviously requires a serious rethinking of both the problem of killing in general and our attitude towards people who are taught to kill. The book is based on numerous interviews and the results of modern psychological, tactical and historical research. It is included in the list of recommended reading in the US Marine Corps.