On Killing Book Summary - On Killing Book explained in key points

On Killing summary

Brief summary

On Killing by Lt. Col. Dave Grossman delves into the psychological and physiological effects of killing in combat. It examines the resistance to killing, the historical changes in the willingness to kill, and the implications for society.

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    On Killing
    Summary of key ideas

    Understanding the Psychology of Killing

    In On Killing by Lt. Col. Dave Grossman, we delve into the psychology of killing in combat. Grossman begins by discussing the natural resistance humans have to killing one another, a phenomenon he calls 'killology'. He explains that this resistance is a result of our innate aversion to killing members of our own species, a trait that has been crucial to our survival as a species.

    Grossman then explores the ways in which the military has historically addressed this resistance. He discusses the development of new training methods, such as the use of human-shaped targets, to desensitize soldiers to the act of killing. He also examines the role of distance and impersonal weapons in reducing the psychological barriers to killing, as seen in the rise of long-range weaponry.

    The Evolution of Killing

    As we move forward in On Killing, Grossman discusses the evolution of killing in warfare. He explains how, in the past, soldiers were more likely to kill at close range, leading to a higher incidence of psychological trauma. However, with the advent of long-range weapons, soldiers could kill from a distance, reducing the psychological impact on the individual.

    Grossman also explores the role of conditioning in desensitizing soldiers to killing. He discusses the military's use of operant conditioning, a method that rewards soldiers for successful kills, and classical conditioning, which associates the act of killing with positive emotions such as camaraderie and patriotism.

    The Aftermath of Killing

    Shifting gears, On Killing delves into the aftermath of killing in combat. Grossman discusses the psychological impact of killing on soldiers, including the development of post-traumatic stress disorder (PTSD). He explains that the psychological trauma of killing is not only a result of the act itself but also the moral and ethical implications that follow.

    Grossman also explores the concept of 'moral injury', a term used to describe the psychological distress caused by actions that violate one's moral or ethical code. He explains that soldiers who experience moral injury often struggle with feelings of guilt, shame, and a loss of meaning, leading to severe mental health issues.

    Looking Towards the Future

    In the latter part of On Killing, Grossman discusses the implications of his research on the future of warfare. He argues that the increasing use of long-range weapons and unmanned drones, while reducing the psychological impact on individual soldiers, may lead to a greater disconnect between the act of killing and its consequences.

    Grossman also emphasizes the importance of understanding the psychological impact of killing on soldiers and the need for better mental health support. He suggests that by acknowledging the psychological cost of killing, we can work towards creating a more humane and ethical approach to warfare.


    In conclusion, On Killing by Lt. Col. Dave Grossman provides a comprehensive exploration of the psychology of killing in combat. It sheds light on the natural resistance humans have to killing, the methods used to overcome this resistance, and the psychological impact of killing on soldiers. It also raises important ethical and moral questions about the future of warfare and the well-being of those who are asked to kill in our name.

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    What is On Killing about?

    On Killing by Lt. Col. Dave Grossman explores the psychological and physiological effects of killing in combat. Through extensive research and real-life accounts, Grossman examines the history and methods of training soldiers to overcome their natural resistance to taking another human's life. He also delves into the societal and ethical implications of warfare and the long-term impact on those who have participated in it.

    On Killing Review

    On Killing (1996) explores the psychological and physiological effects of killing in the context of combat and warfare. Here's why this book is worth reading:

    • With in-depth research and interviews with soldiers and military experts, it offers a unique understanding of the realities and consequences of taking human lives.
    • By examining the history and evolution of training methods and techniques, the book sheds light on the human reluctance to kill and the measures taken to overcome it.
    • Examining the ethical and moral implications of killing, On Killing prompts readers to reflect on the complex nature of violence and its impact on individuals and society.

    Who should read On Killing?

    • Individuals interested in understanding the psychological and ethical aspects of killing
    • Professionals in fields such as law enforcement, military, or mental health
    • Those seeking insights into the effects of violence on individuals and society

    About the Author

    Dave Grossman is a retired U.S. Army Lieutenant Colonel and a renowned expert in the field of psychology and warfare. Throughout his career, he has taught at West Point and worked as a professor of psychology at the U.S. Military Academy. Grossman has written several influential books, including 'On Killing' and 'On Combat', which explore the psychological and physiological effects of violence and combat on soldiers. His work has had a significant impact on military training and the understanding of the human response to killing.

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    On Killing FAQs 

    What is the main message of On Killing?

    The main message of On Killing explores the psychological effects that combat has on soldiers and the ethical implications of killing in war.

    How long does it take to read On Killing?

    The estimated reading time for On Killing varies depending on the reader, but it typically takes several hours. However, the Blinkist summary can be read in just 15 minutes.

    Is On Killing a good book? Is it worth reading?

    On Killing is a thought-provoking and insightful book that offers valuable insights into the realities of warfare. It is definitely worth reading.

    Who is the author of On Killing?

    The author of On Killing is Lt. Col. Dave Grossman.

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