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Killology[1][2] is the study of the psychological and physiological effects of killing and combat on the human psyche; and the factors that enable and restrain a combatant's killing of others in these situations.

The term and field of study was invented by Lt. Col. Dave Grossman (US Army, Ret.) of the Killology Research Group in his 1996 book On Killing: The Psychological Cost of Learning to Kill in War and Society.[3][4]

The soldier's choice[edit]

Grossman claims in his book On Killing that soldiers are faced with four options once they have entered into combat.[5] These are:

  1. Fight: As the name implies, this is the standard that defines the soldier’s role as actively trying to defeat the enemy by use of their training.
  2. Flight: This option involves the combatant fleeing the engagement.
  3. Posture: This action involves the soldier falsely showing active participation in combat. In actuality they are not being effective in deterring the enemy from success. This is a major point of concern for commanders as it is difficult to tell the difference between a soldier posturing or fighting.
  4. Submit: Submission to the enemy during an engagement is a direct act of surrender. In the animal kingdom, this is used by lesser combatants to prevent them from being injured after they can ascertain the triviality of their battle.

The problem of non- or mis-firing soldiers[edit]

S.L.A. Marshall did a study on the firing rates of soldiers in World War II. He found that the ratio of rounds fired vs. hits was low; he also noted that the majority of soldiers were not aiming to hit their targets.[6] This was a problem for the US military and its allies during World War II. New training implements were developed and hit rates improved. The changes were small, but effective. First, instead of shooting at bull's-eye type targets, the United States Army switched to silhouette targets that mimic an average human. Training also switched from 300 yard slow fire testing to rapid fire testing with different time and distance intervals from 20 to 300 yards. With these two changes, hitting targets became a reaction that was almost automatic.

Some authors have discredited S.L.A. Marshall's book, stating that the book may be more of an idea of what was occurring and not a scientific study of what was happening. Other historians and journalists have outright accused Marshall of fabricating his study.[7]

Another important factor that increased fire and hit rates is the development of camaraderie in training. Soldiers are taught that their actions do not only help or harm themselves, but the whole unit.[8][original research?] This recurring theme in recollections collected from war veterans is the idea that they were not fighting for themselves at the time but more concerned for the people to their left and right. This ideology is ancient and was recorded by Sun Tzu in his book The Art of War: "If those who are sent to draw water begin by drinking themselves, the army is suffering from thirst."[9]

Increase in PTSD since World War II[edit]

Some research has been done to say that the increase of Post-Traumatic Stress Disorder (PTSD) in the military is caused by the increase of firing rates.[5] This brings up the classic debate of correlation vs. causation. Many believe that other factors have been influencing PTSD such as decompression time after conflicts, and the lack of moral sovereignty in engagements.[5]

World War II and Vietnam[edit]

Vietnam is viewed by some[who?] as a less popular war than World War II. Many people who were sent to fight there thought that there was no reason for the engagement and did not feel a moral obligation to fight. In World War II many felt that they were stopping an evil empire from overtaking the globe. This helped the World War II troops' mettle to be steadfast.[original research?]

Another problem with PTSD rates after World War II is the fact that there is far less decompression time for the soldiers.[5] During World War II the main way back home was on a boat trip that took weeks. This time was spent with others who had had similar experiences and could understand the problems faced by others.[5] During Vietnam soldiers were sent via draft to one year rotations by plane. When you arrived to your unit it was usually by yourself and you were shunned. This shunning was a result of the senior members being afraid to befriend someone who had a much higher chance of being killed than the experienced combatants. Once your time in country was over you were once again sent back home by yourself. There may have been other veterans with you but they were from a plethora of other units and you did not know them well enough to share the hardships you had seen.

Finally one of the worst displays of environmental stressors was once you made it back home you were demonized by the public and discarded as a human being. Compare that to the treatment World War II veterans received when they came home from the European Theatre or the Pacific Theatre. Parades were thrown, everyone thanking the soldiers, even the invention of V for Victory was made to quickly show military members support. That symbol was changed into the Peace sign and used to show disapproval of the war in Vietnam just a few years later. These factors among many others caused Vietnam to have the highest postwar depression, suicide, and PTSD rates. To this day many are only now getting the counseling that they need to overcome the mental problems brought upon them from their service in Vietnam.[5]

Modern engagements[edit]

In engagements in the modern era such as the Persian Gulf War through the Iraq War and War in Afghanistan there is still a problem with a lack of decompression time. The training has improved so you train and deploy with the people you will be fighting with.[10] But many times when you reach home you are given time off, and if one is in a reserve unit you most likely go back to work and only see your brothers in arms once a month. This lack of time to debrief and decompress can cause a feeling of isolation that only worsens the effects of PTSD. Grossman states in his book that everyone who experiences combat comes back with PTSD, the only question is to what extent their mind and psyche are damaged and how they cope with it.


Grossman's theory, based on the World War II research of S.L.A. Marshall, is that most of the population deeply resists killing another human. Some veterans and historians have cast doubt on Marshall's research methodology.[11] Professor Roger J. Spiller (Deputy Director of the Combat Studies Institute, US Army Command and General Staff College) argues in his 1988 article, "S.L.A. Marshall and the Ratio of Fire" (RUSI Journal, Winter 1988, pages 63–71), that Marshall had not actually conducted the research upon which he based his ratio-of-fire theory. "The 'systematic collection of data' appears to have been an invention."[12] This revelation has called into question the authenticity of some of Marshall's other books and has lent academic weight to doubts about his integrity that had been raised in military circles even decades earlier.[13]

As a result of Marshall's work, modern military training was modified to attempt to override this instinct, by:

  • using man-shaped targets instead of bullseye targets in marksmanship practice
  • practicing and drilling how soldiers would actually fight
  • dispersing responsibility for the killing throughout the group
  • displacing responsibility for the killing onto an authority figure, i.e., the commanding officer and the military hierarchy (See the Milgram experiment)

By the time of the United States involvement in the Vietnam War, says Grossman, 90% of U.S. soldiers would fire their weapons at other people.

He also says the act of killing is psychologically traumatic for the killer, even more so than constant danger or witnessing the death of others.

Grossman further argues that violence in television, movies and video games contributes to real-life violence by a similar process of training and desensitization.

In On Combat (Grossman's sequel to On Killing, based on ten years of additional research and interviews) he addresses the psychology and physiology of human aggression.

See also[edit]


  1. ^ "Lt. Col. Dave Grossman, the "Killologist" Training America's Cops". Men's Journal. Retrieved 2017-05-07.
  2. ^ "Killology dictionary definition | killology defined". Retrieved 2017-05-07.
  3. ^ Wardrip-Fruin, Noah; Harrigan, Pat (January 2004). First Person: New Media as Story, Performance, and Game. Cambridge, Massachusetts: MIT Press. p. 102. ISBN 978-0-262-23232-6.
  4. ^ Steuter, Erin; Wills, Deborah (15 July 2009). At War with Metaphor: Media, Propaganda, and Racism in the War on Terror. Lexington Books. p. 57. ISBN 978-0-7391-3031-5.
  5. ^ a b c d e f Grossman, Dave (1996). On killing : the psychological cost of learning to kill in war and society. Boston: Little, Brown. p. 367. ISBN 978-0-316-33000-8. OCLC 32312539.
  6. ^ Marshall, S. L. A. (Samuel Lyman Atwood) (2000). Men against fire: the problem of battle command. Norman, Okla.: University of Oklahoma Press. ISBN 978-0-8061-3280-8.
  7. ^ Hunter, Evan (December 12, 2007). "Fire Away". Newsweek.
  8. ^ Kyle, Chris (2012). American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History. New York: W. Morrow. ISBN 9780062082374.
  9. ^ Sun Tzu, 6th century BC; Minford, John (2006). The Art of War. New York: Penguin Books. ISBN 978-0-14-303752-1.
  10. ^ Wright, Evan (2005). Generation kill: Devil Dogs, Iceman, Captain America, and the new face of American war. New York: Berkeley Caliber. ISBN 9780425200407.
  11. ^ Robert Engen. "Killing for Their Country: A New Look At "Killology" (Canadian Military Journal, Vol. 9, No. 2)". Archived from the original on 2011-07-21. Retrieved 2011-05-08. As a military historian, I am instinctively skeptical of any work or theory that claims to overturn all existing scholarship – indeed, overturn an entire academic discipline – in one fell swoop...[however] Lieutenant Colonel Grossman’s appeals to biology and psychology are flawed, and that the bulwark of his historical evidence – S.L.A. Marshall’s assertion that soldiers do not fire their weapons – can be verifiably disproven.
  12. ^ Spiller, Roger J. (Winter 1988). "S.L.A. Marshall and the Ratio of Fire". RUSI Journal. pp. 63–71..
    (Extracts are available on-line in an article criticizing Marshall)
  13. ^ Hunter, Evan (December 12, 2007). "Fire Away". Newsweek.

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