Natural Killers —Turning the Tide of Battle
by Major David S. Pierson, US Army

I stepped over to greet the tank company commander as he approached the tactical operations center. This man was a neighbor and a friend, but he was not the same soldier I had briefed three days earlier.  After 72 hours of combat, his eyes were sunken and dark. The left side of his face was stained with iodine and bandaged to cover a bullet wound received 14 hours earlier. He was distant and detached as he described an incident that had occurred just hours before. His company had engaged two Iraqi trucks moving across its front. The trucks exploded and Iraqi soldiers leapt out of them on fire. The company then finished them off with coaxial machineguns and a single sabot round that vaporized the soldier it hit. My friend was clearly shaken by the episode.  This man was a warrior. Circumstances had made him a killer.

My friend wasn’t a natural killer. A natural killer is a person who has a predisposition to kill—he enjoys combat and feels little or no remorse about killing the enemy. These men have existed throughout the history of warfare, and their feats have often been hailed as heroic. They constitute less than 4 percent of the force, yet some studies show that they do almost half of the killing. These men rarely distinguish themselves before the moment arrives to pull the trigger. It is only after the smoke has cleared that the full impact of their accomplishment is seen. It is important to identify natural killers before combat, because these soldiers are both a vital asset and a potential liability—correctly positioning them in a unit can turn the tide of battle. To better understand the importance of identifying these soldiers, one should understand what makes soldiers kill, the characteristics of natural killers and their battlefield capabilities and limitations.

Thou Shall Not Kill

pierson1.jpg (8892 bytes)A chaplain provides field service to soldiers of the 101st Airborne Division (Air Assault).  

Most soldiers are unknowingly conscientious objectors.1 They try to avoid taking a human life. This is not a bad thing. Rather, it is a reflection of a strong moral upbringing. Getting most soldiers to pull the trigger on another human being requires great effort. In World War II, General S.L.A. Marshall studied infantry unit firing ratios and concluded that only 15 to 25 percent of infantrymen ever fired their weapons in combat. In general, those on specialty and crew-served weapons were firers, while the nonfirers were almost exclusively riflemen.2 In On Killing, David Grossman points out that there are three things that make soldiers kill: conditioning, recent experience and temperament.3

Soldiers can be conditioned individually and collectively to pull the trigger. Individual conditioning includes gunnery and rifle ranges where pop-up human shaped targets are rapidly engaged without thought. The trigger-pull response becomes automatic. Close supervision also affects firing rates. Men pull the trigger more frequently under supervision or in groups, hence a higher ratio of firing among key weapons. Artillery, the greatest killer on the battlefield, has always killed in teams. We indirectly condition soldiers to kill by training them as killing teams. Recognizing that men had to be conditioned to fire, the Army changed its training programs after World War II, and firing rates during the Korean War rose to 55 percent.4 This figure reached 95 percent during the Vietnam War.5 Soldiers can be taught to pull the trigger, but that does not guarantee that the bullet will find the target.

Recent experiences, such as the death of a comrade, can cause soldiers to kill the enemy out of revenge or frustration. This is a temporary condition resulting from combat stress. It is based upon emotion and can subside as quickly as it occurred. In an American field hospital in Vietnam, a wounded Vietcong dragged himself out of bed and used a broken bottle to slit the throat of an Australian lying next to him. The American doctor, who had worked for hours to save the Australian’s life, grabbed a .45, shoved it in the Vietcong’s mouth and, with no regard for the Hippocratic Oath, blew his brains out. When he realized what he had done, he went insane and had to be shipped home.6 While we may attempt to emotionally condition soldiers through propaganda, it has little long-term effect on them on the battlefield.

A temperament for killing exists among some human beings. Marshall, in identifying the battlefield fighters, said, "the same names continued to reappear as having taken the initiative, and relatively few fresh names were added to the list on any day."7 A post-World War II study by R. L. Swank and W. E. Marchand proposed that 2 percent of soldiers were "aggressive psychopaths" who did not suffer from the normal remorse or trauma associated with killing.8 I use the word suffer because when the job of the soldier is to kill, those fettered by their conscience are suffering while doing their job. We tend to shun the concept of the willing killer because it offends our kinder sensibilities, but a controlled psychopath is an asset on the killing fields. Those who possess such a temperament are natural killers and many have served this country well. The problem lies in identifying these individuals and positioning them where they can be most effective.

Killers Among Us

The term psychopath conjures up images of movies such as Psycho or Silence of the Lambs. There are less inflammatory terms such as sociopath, antisocial personality type or undercontrolled personality type that apply to the same people. The meanings of these terms have changed and interchanged over the last half-century. Psychopath is now associated almost exclusively with violent actions rather than a propensity for violence.9 The last three terms are still used somewhat interchangeably to denote someone who lacks social emotions and often resorts to violence, deception or manipulation as a means to get what he wants. These people constitute 3 to 4 percent of the male population and 1 percent of the female.10 Such people who enter the military are not monsters waiting to be released. They can be level-headed, productive soldiers, and if put into the right situation, they will kill the enemy aggressively and without remorse. If these soldiers are in our units, how can we identify them?

A predisposition to kill is the result of genetics and early childhood experience. There are common traits that are indicative of natural killers. While the collection of these traits is not absolutely deterministic of a killer, it is a good framework for identifying those who may have this propensity. In general, the natural killer found in the US Army lacks social emotions, is a later son (not first-born), got into frequent fights as a child, enjoys contact sports, is from a middle or upper class background, is an extrovert, has above-average intelligence and a caustic sense of humor.

While no specific violence gene has yet been isolated, there is ample evidence to suggest that violent tendencies are inherited. Researcher D.C. Rowe posits that some individuals have a genotype that disposes them to antisocial behavior.11 These individuals are characterized by a deficit of social emotions which include love, shame, guilt, empathy and remorse. They are keen predictors of other people’s behavior. Unbridled by emotions, they rely solely on actuarial data to predict outcomes, never resorting to feelings or hunches.12 They focus on short-term outcomes without taking into account the emotional reactions of those with whom they are dealing. Thus they may come across as cold, impersonal and manipulative.

As previously mentioned, the natural killer is most likely not a first-born son. Later sons are generally more aggressive and have less fear or anxiety in dangerous situations. An Israeli Defense Force study of its officers from 1961 to 1966 showed that "first borns" were more anxious than "later borns" and that they generally sought less dangerous positions in the military. Later borns were more likely to volunteer for combat and had a better chance of encountering terrorists on patrols.13 A study of Korean War fighter plane aces found that first borns engaged the enemy less and were more anxious about flying.14 Family position also seems to relate to assassins. Almost all American assassins have been later sons—John Wilkes Booth, Charles Giteau and Lee Harvey Oswald, to name three.15 Later borns, by virtue of being routinely dominated by their siblings, ultimately feel less fear during stressful situations. They also feel the need to prove their worth over their siblings and more quickly accept dangerous challenges.

A natural killer has been a fighter for much of his life. Frequent fighting as a child does not mean the individual was a bully. Rather, he chose to respond to stressful situations with aggression.16 Arthur J. Dollard concluded that aggression is the result of frustration and this is a normal human reaction.17 The sociopath, also referred to as the undercontrolled aggressive personality type, has low internal controls against violence and will resort to aggressive behavior unless constrained by rigid external controls. Such a person can be conditioned to not respond to frustration with external aggression.18 Thus, if frustrated by a Drill Sergeant’s control, the undercontrolled personality type will refrain from direct aggression and look for another target for his aggression. The military provides ample displacement outlets for this aggression in the form of physical training, field maneuvers and weapons ranges. It is the perfect environment for a sociopath to excel.

The natural killer is an aggressive athlete whose physical makeup allows him to excel at contact sports. Combative sports provide long-term training in aggression while acting as a short-term catharsis or safety valve for aggressive individuals.19 An Army-funded study of Korean War veterans discerned differences in the characteristics of fighters—those who took aggressive action in combat—versus nonfighters—those who were hysterical or nonresponsive in combat. This study, conducted by the Human Resources Research Office (HumRRO), concluded that the fighters had been more active in contact sports such as football, boxing or hockey. It also concluded that fighters had a high masculinity factor or outdoors adventurousness about them. Their body types were larger; on average they were an inch taller and eight pounds heavier than the nonfighters.20 They were rugged individuals who had channeled their aggressions through contact sports.

Another discriminator for identifying natural killers is their socio-economic background. Natural killers usually come from a middle or upper class background. The volunteer military has had the luxury to pick and choose those who will be allowed into the service, and we exclude those with criminal records. Sociopaths follow a "cheater strategy" to obtain what they want.21 The lack of a social conscience allows the sociopath to cheat without remorse. Consequently, those who find themselves in the economically disadvantaged lower class will resort to crime unless placed in a highly controlled environment. In other words, a sociopath from a depressed economic background will most likely have a criminal record, and under today’s standards, he would not be able to enter the military. Thus, natural killers in the US military will most likely come from a middle or upper class background.

Sociopaths are generally extroverts. One reason for this is the inheritance of a nervous system that is relatively insensitive to low levels of stimulation. Individuals with this physiotype tend to be extroverted.22 They also have lower than average levels of adrenaline and seek experiences to heighten this. Extroverts and sociopaths are less affected by threats of pain or punishment, and they have greater tolerance of actual pain or punishment. Both sociopaths and extroverts will approach a situation that most people will avoid.23 These factors were confirmed by the HumRRO study conclusion that fighters were extroverted, spontaneous and relatively free from anxiety.24

The natural killer has above-average intelligence. Like sociopaths with no economic resources, those without above-average intelligence end up in jail. Therefore, sociopaths in our military are usually intelligent. The HumRRO study found that the intelligence quotient (IQ) of fighters was, on average, 13 points higher than nonfighters’. The study subjects were all infantrymen and the mean group IQ was only 85, 15 points below the national average of 100. This indicated that less intelligent men were sent forward to fight, but within that group, the more intelligent ones were better fighters.25

Additionally, the natural killer has a caustic sense of humor that relies on sharp wit and biting sarcasm.26 Such hostile humor acts as a tension-discharger, a relief valve. While we normally associate humor with friendly behavior, laughter itself is a primarily aggressive behavior. Laughter is usually directed at someone and is infectious, with the unspoken agreement being to "join in or not be part of the group."27 With aggression as the underlying theme, the natural killer enjoys humor.

Potential natural killers can be identified through long-term observation testing. Supervisors can look for natural killer traits in their soldiers. Over time, they will develop a close enough relationship with their soldiers to be able to distinguish those who match most of the characteristics of killers. Personality-type testing may also identify natural killers. One such test already in use by the military is the Myers-Briggs personality-type test. Considering the characteristics discussed above, the natural killer would most likely be an ESTP (extroverted, sensory, thinking, perceiving) personality type on this test. ESTPs are outgoing, highly adaptive, deal in facts, sensory oriented, excel at sports, learn through life experience, prefer action to conversation and are tough in harsh situations.28 Matching the ESTP personality type to intelligent, caustic, later sons will help identify potential natural killers. The ESTP personality type, coupled with the other associated traits, is not an absolute determinant of a natural killer or a sociopath, but it provides a good baseline. Personality-type testing at initial entry could identify and help place natural killers where they can best employ their talent—in infantry, armor and special operations units.

Cry Havoc

The individual soldier does make a difference on the killing fields. The natural killer is a vital asset to a unit because he is a killing machine that will turn the tide of battle when the chips are down. During World War II, 40 percent of the US Army Air Forces’ air-to-air killing was done by 1 percent of its pilots.29 Marshall’s work and the HumRRO study both found that a small percentage of soldiers did most of the fighting. It is not enough to rely on conditioning to produce killers—genetics and childhood environment have already molded them.

Natural killers bring some obvious advantages to a unit. They will personally kill the enemy in droves. They are natural leaders who will motivate other soldiers to kill. They are also fiercely competitive and will aggressively pursue victory. In a battle of attrition, the natural killer can single-handedly tip the scales. However, there are drawbacks to natural killers in a unit too. Their highly aggressive nature may act as a catalyst for violence in tenuous situations such as peacekeeping (PK) operations. This is not to say that they will create atrocities, which are generally initiated by overcontrolled personality types in second-in-command positions, not by undercontrolled personality types.30

Atrocities are the result of the release of pent-up hostilities—not a characteristic of sociopaths who live for the moment. Natural killers may participate in atrocities but they will not initiate them. This same "live-for-the-moment" attitude makes the peacetime routine difficult for killers. The sociopath craves stimulation that the peacetime Army often does not provide. Marshall concluded that many of the best fighters spent significant amounts of time in the stockade—"They could fight like hell but they couldn’t soldier."31 Consequently, many of these individuals seek out fast-paced specialty units such as Airborne, Ranger or Special Forces units.32 The natural killer will become bored in a regular unit and may seek the stimuli of sports, fighting or drugs. Natural killers are motivated by competition and excitement, not a sense of sacrifice—they are not the kind of soldiers who will leap on a grenade to protect others.

Another characteristic of the natural killer is to usurp authority in a crisis to turn the tide of battle. Marshall wrote of a sergeant whose actions had carried the battle and yet he had not been recommended for a decoration. When his company commander was asked why, he replied, "When the fighting started he practically took the company away from me. He was leading and the men were obeying him. You can’t decorate a man who’ll do that to you."33

pierson2.jpg (9595 bytes)Soldiers of the 193d Infantry Brigade prepare to return fire during Operation Just Cause, December 1990.

There are several considerations for the positioning of natural killers in the unit. If they are junior enlisted personnel, they should be assigned to a crew-served weapon. This will provide them with ample firepower and place them in a position to motivate others. They will naturally seek this position out anyway. If the natural killer is a noncommissioned officer or officer, assign him to a leadership position where he will supervise trigger pullers and will have a weapon system at his disposal. Here they will lead by example, killing the enemy and motivating others to do so as well.

Natural killers may be spread out in the unit or concentrated, depending on the tactical situation. The typical officer cannot single-handedly lead an entire company in combat.34 By spreading out those who will carry the day you increase your chances for success in battle. Wherever they are placed in a unit though, they may take over command based upon the situation and the leaders around them. This may be desirable depending upon the quality and number of your other leaders. You can "backstop" leaders of unproved ability with natural killers. If there is a well-defined decisive point of the battle, the commander may choose to place natural killers at that point. They will provide that final measure of resolve in the assault or become the defense linchpin. Since natural killers are motivated by competition and excitement, they should not be placed in a reserve position, where they would have to patiently wait, then hurl themselves into the breach on command. Quick to take charge, they will move to the sound of the guns unless tightly controlled. In PK operations, keep them in positions where they will not habitually deal with potential combatants. This will minimize the risk of escalating the tension into violence. Likewise, during peacetime operations, keep them active in exercises, schools or in sports. They will seek out these activities themselves to stay stimulated.

Too often we find out about the lethality of an individual soldier after the fact, when he has saved the unit and been nominated for a valorous award. If you knew before hand who was likely to rise up and save the day, you could place these soldiers at the battle’s decisive point and enhance your chances of success. Natural killers are out there in your unit right now—find them and use them wisely. MR


1. S.L.A. Marshall, Men Against Fire: The Problem of Battle Command in Future War (Washington DC: Infantry Journal Press, 1947, reprint Gloucester, MA: Peter Smith, 1978), 79.
2. Ibid., 56-57.
3. Dave Grossman, On Killing: The Psychological Cost of Learning to Kill in War and Society (Boston, MA: Little, Brown, and Company, 1996), 177-85.
4. Marshall, 9.
5. Grossman, 35.
6. Mark Baker, Nam (New York: William Morrow and Company, 1981), 161-62.
7. Marshall, 58-59.
8. Swank and Marchand, in On Killing, 180.
9. Ralph Serin, "Can Criminal Psychopaths be Identified?" FORUM 1989, Volume 1, Number 2.
10. C.C. Strauss and B.B. Lahey in: The Sociobiology of Sociopathy: An Integrated Evolutionary Model, Linda Mealey, unedited penultimate draft of an article accepted for publication (Copyright 1994: Cambridge University Press).
11. D.C. Rowe, "Inherited dispositions toward learning delinquent and criminal behavior: New evidence," in Crime in biological, social, and moral contexts, ed. L. Ellis and H. Hoffman (Praeger Publications, November 1990), 122.
12. Linda Mealey, in The Sociobiology of Sociopathy, 3.
13. Peter Watson, War on the Mind: The Military Uses and Abuses of Psychology (New York: Basic Books Inc., 1978), 51.
14. E.P. Torrence, The development of preliminary life-experience inventory for the study of fight-interceptor combat effectiveness, Research Bulletin AFPTRC-TR-54-89, Lackland Air Force Base, San Antonio, TX, December 1954.
15. Irving D. Harris, Violence: Perspectives on Murder and Aggression (San Francisco: Jossey-Bass Publishers), ed. Irwin L. Kutash, Samuel B. Kutash and Louis B. Schlesinger, 203.
16. Grossman, 182.
17. J. Dollard et al., Frustration and Aggression (New Haven, CT: Yale University Press, 1939).
18. Edwin I. Magargee and Jack E. Hokanson, The Dynamics of Aggression: Individual, Group and International Analyses (New York: Harper & Row, 1970), 111.
19. Irenaus Eibl-Eibesfeldt, The Biology of Peace and War: Men, Animals, and Aggression (New York: The Viking Press, 1979), translated from German by Eric Mosbacher (R. Piper & Co., Munich), 110-11.
20. Watson, 49-50.
21. Mealey, 33.
22. Ibid., 17.
23. Ibid., 14.
24. Watson, 49.
25. Ibid.
26. Ibid.
27. Eibl-Eibesfeldt, 90.
28. Isabel Briggs Myers, Gifts Differing (Palo Alto, CA: Consulting Psychologists Press, 1980), 101-104.
29. Grossman, 181.
30. Watson, 245.
31. Marshall, 60-61.
32. Grossman, 181.
33. Marshall, 62.
34. Ibid.

Major David S. Pierson is the 165th Military Intelligence Battalion XO, Darmstadt, Germany. He received a B.A. from the University of Georgia and an M.A. from Webster University, and he is a graduate of the US Army Command and General Staff College (CGSC). He has held a variety of command and staff positions in the Continental United States and Germany, including G2 operations officer, V Corps, Heidelberg, Germany; chief, collection management, United States Transportation Command, Scott Air Force Base, Illinois; and commander, A Company, 124th Military Intelligence Battalion, Fort Stewart, Georgia.

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