The Greatest Mistake in Combat Psychology

How Civilization Caused Psychologists to Misunderstand War, Morality, and Human Nature

My grandfather, Carl Johan Larsen, grew up on a farm in the Danish community of Danevang, Texas.

There was no grocery store.

There was no butcher shop.

Everything the family ate was grown, raised, harvested, or processed by hand.

If they ate chicken, it was because they had raised a chicken, killed it, plucked it, cleaned it, and cooked it.

Often preparing the chicken would fall to a young boy.

Processing animals was not a special event.

It was a chore.

Just another task that had to be done.

The boys fed animals.

Collected eggs.

Worked in the fields.

Cut wood.

And when it was time to eat chicken, they helped kill and clean chickens.

The first time they saw blood was not extraordinary.

The first time they saw and smelled internal organs was not extraordinary.

Those lessons were learned gradually over years, woven into the ordinary rhythms of life.

If they ate bacon with breakfast or ham at Christmas, it was because they had raised a hog, killed it, cleaned it, butchered it, and preserved it long enough to eat.

Death was not hidden.

It was part of life.

Like many boys of his generation, he learned from childhood that life feeds on life.

Later he became a nose gunner on a B-17 during the Second World War.

He flew in the most dangerous phase of the American daylight bombing campaign over Europe. Just five months before his aircraft was shot down, the Eighth Air Force lost 148 bombers and approximately 1,500 aircrew during "Black Week." On one mission alone, 60 B-17s were shot down. The losses were so severe that crews often spoke less about completing their tours than about how long their luck would hold. Few men expected to finish the war unscathed. Many doubted they would finish it alive.

He was a bombardier, operating the aircraft’s Norden bombsight over targets, and also manned the twin .50 caliber machine guns in the nose.

On his seventeenth mission, flying as a substitute with a crew that was not his own, his aircraft was attacked by a German Messerschmitt in a head-on pass. Cannon fire severely wounded the navigator and crippled the bomber. Despite losing more than one engine, and having several wounded crewmen, including my grandfather, they managed to keep the aircraft in the air long enough to reach neutral Switzerland, where they bailed out. The severely wounded navigator successfully bailed out, but was unable to deploy his parachute, and was killed.

For most men, survival would have been enough. Interned in Switzerland for the remainder of the war, he escaped, was recaptured, and escaped again. On his second escape attempt, he paddled across a lake under cover of darkness to make it into Italy where American troops were in control. He eventually made his way back to England to returned to the war.

Like many of his generation, raised to be a farmer, when called upon by his country Carl Larsen was a warrior.

Yet it is important to understand what my grandfather was not.

He was not a violent man.

He was one of the most civilized men I have ever known.

He was kind.

Honest.

Gentlemanly.

Well-mannered.

Deeply devoted to his family, his community, and his country.

He possessed a strong sense of personal responsibility and obligation to others.

Years later, after I had become a soldier myself and had seen a little combat, while we were hunting and talking about his experiences, he shared a lesson I have never forgotten.

“The first time a man smells viscera, it shouldn’t be his friend’s.”

At first glance, this may sound like a lesson about hunting.

It was not.

It was a lesson about reality.

My grandfather had grown up in a world where death was visible. He had smelled blood. He had handled dead animals. He understood from childhood that life, death, injury, and survival were inseparable parts of existence.

What he was telling me was that there is a cost to encountering these realities for the first time under the worst possible circumstances.

For most of human history, people learned such lessons long before they ever encountered warfare.

Today, many people reach adulthood having never encountered them at all.

That difference matters.

In fact, it may help explain some of the greatest mistakes in twentieth century combat psychology.

Nature Is Not Sentimental

My grandfather’s lesson reflected a reality that modern people rarely encounter.

For most of human history, human beings lived much closer to nature than we do today.

And nature is not sentimental.

Every animal eventually dies.

Most do not die peacefully.

They die from disease.

They die from injury.

They die from starvation.

They die from exposure.

Many are killed and consumed by other animals.

Predation is not an exception in nature.

It is one of the fundamental processes through which life operates.

Life feeds on life.

As Jack London’s Wolf Larsen observed, “Where there is room for one life, she sows a thousand lives...”

Whatever one thinks of his conclusions, London understood something modern people often forget. Nature is not organized around comfort, fairness, or the preservation of every individual life.

A deer torn apart by wolves.

A rabbit carried off by a hawk.

A chimpanzee killing a rival male.

A human hunter butchering an animal for food.

These are not aberrations.

They are ordinary features of the natural world.

For hundreds of thousands of years, human beings observed these realities from childhood.

Children watched animals butchered.

They watched livestock slaughtered.

They saw predators kill prey.

They saw injury.

They saw disease.

They saw death.

Long before they were old enough to participate in hunting or warfare themselves, they understood that life was fragile and survival was never guaranteed.

This does not mean they were cruel.

Quite the opposite.

People who live close to these realities often develop a profound respect for life precisely because they understand how easily it can be lost.

My grandfather was not hardened by understanding death.

He was civilized while understanding it.

That distinction matters.

Modern civilization has created an unprecedented degree of separation from these realities.

Many people can now reach adulthood without ever seeing an animal butchered.

Without seeing a dead body.

Without witnessing serious violence.

Without understanding where food comes from beyond a supermarket shelf.

Without ever confronting the realities that sustained human existence throughout nearly all of our evolutionary history.

This separation has obvious benefits.

Civilization is one of humanity’s greatest achievements.

Yet it also creates a danger.

People may begin to mistake their distance from reality for reality itself.

Ideas emerge that would have been incomprehensible to our ancestors not because our ancestors were less moral, but because they lived in circumstances where survival imposed different demands.

The question is not whether civilization has made life safer and more humane.

It unquestionably has.

The question is whether a population largely insulated from the realities that shaped human evolution can accurately understand the psychology of those realities.

The answer to that question lies at the heart of one of the greatest mistakes in combat psychology.

The Civilization Problem

Modern people often assume their moral intuitions are universal.

They are not.

They are products of a particular environment.

For hundreds of thousands of years, every human being lived as a member of a hunter-gatherer band.

The survival of the group depended directly upon its ability to acquire resources and defend them.

Human beings hunted because failure to hunt meant starvation.

Human beings fought because failure to fight meant displacement, enslavement, or death.

Neighboring groups competed for territory, water, game, and other resources. Groups unable or unwilling to defend themselves disappeared.

This was not a specialized activity performed by a minority of the population.

It was the human condition.

The moral systems that evolved in these environments reflected those realities.

Courage was a virtue.

Loyalty was a virtue.

Competence was a virtue.

Willingness to contribute to group survival was a virtue.

Failure to contribute was not viewed as a harmless personal preference.

It imposed costs on everyone else.

As a result, hunter-gatherer societies developed powerful mechanisms for enforcing participation.

Ridicule.

Shaming.

Loss of status.

Ostracism.

Expulsion.

Anthropologists have documented these mechanisms repeatedly across small-scale societies (Boehm, 1999).

This should not surprise us.

For most of human history, survival could not be outsourced.

Imagine a young man in a hunter-gatherer band announcing that he does not wish to hunt.

He does not wish to defend the group.

He does not wish to participate in coalition obligations.

This would not have been seen as a lifestyle choice.

That assumption itself reflects the moral intuitions of civilization.

In the ancestral environment, others would have to acquire the food he consumed.

Others would have to accept the risks he refused to accept.

Others would have to defend resources from which he benefited.

His reputation would suffer.

His status would suffer.

His influence would suffer.

His opportunities for mating would suffer.

Likely, persistent failure to contribute would result in ostracism or expulsion, and inevitable death.

The issue was not merely economic.

It was moral.

Hunter-gatherer morality evolved specifically to encourage behaviors necessary for group survival and discourage behaviors that threatened it.

This observation leads to an uncomfortable conclusion.

Many moral beliefs common today could not have emerged in the environments that shaped human evolution.

Pacifism is one example.

Not because human beings were naturally bloodthirsty.

But because pacifism depends upon conditions that did not exist.

Pacifism becomes possible when defense can be delegated to others.

It becomes possible when individuals can benefit from security without personally contributing to its provision.

It becomes possible when civilization separates the costs of violence from the benefits of protection.

The same principle applies to many other modern moral intuitions.

They are not necessarily wrong.

But they are historically unusual.

They are products of specialization.

They are products of civilization.

Most importantly, they are not necessarily windows into ancestral human psychology.

As specialization increased, responsibility for managing violence became concentrated in a shrinking portion of the population while increasing numbers of people became insulated from it.

The result was not merely a division of labor. It was the beginning of moral divergence.

Those responsible for providing security remained tied to realities that had shaped human behavior for thousands of generations. Those protected by that security increasingly developed moral intuitions under very different conditions.

Over time, the moral assumptions of the protector and the protected began to diverge.

This distinction lies at the heart of one of the greatest mistakes in combat psychology.

Why Morality Exists

Human beings possess powerful moral instincts.

Across cultures, people admire courage, value loyalty, reward cooperation, condemn cheating, and feel obligations toward family, community, and group. The specific rules may differ, but many of the underlying moral themes appear repeatedly throughout human societies.

The question is what purpose these moral systems serve.

Human beings did not survive as solitary individuals.

We survived as members of coalitions.

Throughout human history, groups competed over food, water, territory, mates, and other resources. Coalitions that cooperated effectively tended to survive and reproduce. Coalitions that failed to cooperate often disappeared.

Morality can be understood as one of the mechanisms that made cooperation possible.

Loyalty encouraged individuals to place the interests of the group above their immediate self-interest.

Reciprocity rewarded cooperation and punished freeloading.

Honor created incentives for courage.

Shame discouraged behaviors that imposed costs on the coalition.

Duty encouraged individuals to accept risks on behalf of others.

Far from being opposed to evolution, these moral emotions can be understood as adaptations to the realities of coalition survival.

More broadly, morality can be understood as a system for aligning individual behavior with the interests of the coalition.

In some circumstances this produces compassion, generosity, and forgiveness.

In others it produces punishment, exclusion, and violence.

The underlying question is often not whether a behavior benefits humanity in the abstract, but whether it benefits the group to which the individual belongs.

This observation has important implications for understanding warfare.

The moral intuitions common in modern industrial societies are not necessarily the same moral intuitions that shaped human evolution.

And that distinction becomes critically important when attempting to understand the psychology of war.

Marshall, Grossman, and the Resistance-to-Killing Hypothesis

The most influential modern argument about combat psychology emerged from the work of S.L.A. Marshall and later Dave Grossman.

Marshall’s book Men Against Fire claimed that only fifteen to twenty-five percent of American infantrymen fired their weapons at exposed enemy soldiers during World War II (Marshall, 1947).

The implication was obvious.

Most soldiers were not shooting.

Why?

Marshall suggested that human beings possessed a powerful resistance to killing members of their own species.

Decades later, Grossman expanded this argument in On Killing (Grossman, 1995).

Grossman argued that military training largely functions by overcoming an innate human reluctance to kill.

His evidence came from several sources:

Marshall’s firing-rate statistics.

Reports of soldiers shooting high.

Examples of ritualized aggression among animals.

Psychological distress experienced by combat veterans after killing.

The argument was elegant.

The problem is that both the evidence and the assumptions behind it are deeply flawed.

First, the Marshall data themselves appear far weaker than most people realize.

Roger Spiller’s review of Marshall’s work found little evidence that the systematic data collection Marshall described had actually occurred (Spiller, 1988).

John Whiteclay Chambers likewise concluded that the empirical foundation supporting Marshall’s famous firing ratios was much weaker than commonly believed (Chambers, 2003).

The most influential statistic in combat psychology may never have rested upon a reliable empirical foundation.

But even if Marshall’s observations were entirely accurate, Grossman’s interpretation does not follow.

The central mistake is the confusion of fear with reluctance to kill.

Combat veterans understand something many psychologists do not.

The dominant emotion in battle is often not guilt.

It is fear.

Fear of being shot.

Fear of being blown apart.

Fear of being trapped.

Fear of watching friends die.

A soldier who hesitates to expose himself long enough to place effective fire on the enemy is not necessarily demonstrating reluctance to kill.

He may simply be demonstrating a healthy desire not to be killed himself.

The courage required in combat is often not the courage to kill.

It is the courage to remain exposed long enough to kill effectively.

This distinction matters because fear requires no elaborate explanation.

Natural selection has been shaping it for hundreds of millions of years.

The same problem appears in Grossman’s interpretation of soldiers shooting high.

Every experienced infantryman knows that inexperienced shooters naturally fire high.

They do so on qualification ranges.

They do so in training.

They do so when no human target is present.

Ordinary marksmanship errors explain the phenomenon perfectly well.

No subconscious resistance to killing is required.

The animal evidence is equally problematic.

Grossman interpreted ritualized aggression as evidence of reluctance to kill.

Evolutionary biology offers a simpler explanation.

Injury is costly.

Animals avoid unnecessary injury because avoiding injury improves survival and reproduction.

No moral reluctance is required.

In fact, some of our closest relatives provide evidence in the opposite direction.

Chimpanzees conduct territorial patrols.

When they encounter isolated rivals and possess overwhelming numerical superiority, they attack.

The critical variable is not aggression.

The critical variable is risk.

As Richard Wrangham’s imbalance-of-power hypothesis argues, coalitionary violence becomes most likely when attackers can act with minimal danger to themselves (Wrangham, 1999).

The objective is not bravery.

The objective is victory.

Researchers have documented chimpanzee groups systematically killing neighboring males and expanding into newly available territory (Mitani et al., 2010; Wilson et al., 2014).

The chimpanzees do not appear traumatized by these victories.

The victorious chimpanzees gain territory.

They gain access to resources.

They gain access to females.

They improve the future prospects of their own group.

The violence is potentially costly.

But from an evolutionary perspective, it is often adaptive.

Human history contains countless examples of similar patterns.

Victorious warriors were frequently celebrated rather than traumatized.

Successful raids could bring territory, resources, prestige, security, and reproductive opportunities.

This does not mean that violence carries no psychological cost.

It means that the act of killing itself cannot automatically be assumed to be psychologically damaging.

Context matters.

Meaning matters.

Whether violence benefits or harms the coalition matters.

This should sound familiar.

Throughout human history, successful warriors were often celebrated precisely because they benefited the coalition.

The pattern is ancient.

The interpretation is modern.

The Video Game Panic

One often forgotten aspect of Grossman’s work is that his theory extended far beyond military psychology.

When On Killing was written, Grossman became one of the most prominent critics of violent media, particularly first-person shooter video games.

He described such games as “murder simulators” and argued that they conditioned children to overcome their natural resistance to killing.

This argument followed directly from the resistance-to-killing hypothesis.

If humans possess a powerful innate reluctance to kill, then repeated exposure to simulated killing should be deeply concerning.

The problem is that subsequent decades of research have failed to support many of the most alarming predictions associated with this theory.

Violent video games may increase short-term aggressive thoughts and physiological arousal, but the dramatic increases in violent criminal behavior predicted by many critics never materialized (Ferguson, 2015).

The significance of this failure extends beyond video games.

It suggests that the underlying theory itself may be weaker than its influence would suggest.

Grossman’s concern about video games is revealing because it demonstrates how broadly the resistance-to-killing hypothesis was applied.

The theory was not merely about combat.

It was a theory of human nature.

And it is that theory that deserves reexamination.

Moral Divergence

The deeper mistake made by legacy psychology was not misunderstanding violence.

It was misunderstanding morality.

Psychologists assumed that the moral intuitions of modern civilization represented universal human nature.

They did not.

They represented a particular stage of social evolution.

The deeper mistake made by legacy psychology was not misunderstanding violence.

It was misunderstanding morality.

As specialization increased, fewer people became responsible for managing violence while increasing numbers became insulated from it.

The result was moral divergence.

Those responsible for providing security continued to confront realities that had shaped human behavior for thousands of generations. Those protected by that security increasingly developed moral intuitions under very different conditions.

The protector and the protected began to inhabit different moral worlds.

To understand moral divergence, it is necessary to understand what morality originally evolved to accomplish.

Morality did not emerge in a vacuum.

It emerged in coalitions.

For hundreds of thousands of years, human beings survived not as isolated individuals but as members of small groups competing with other groups for resources, territory, mates, and survival itself.

In such environments, morality functioned as a mechanism for assigning value to other members of the coalition.

Loyalty mattered because loyal allies increased the group’s chances of survival.

Courage mattered because groups that fled from every threat eventually lost resources, territory, and opportunities.

Reciprocity mattered because individuals who consistently accepted benefits without contributing imposed costs upon everyone else.

Honor mattered because reputation influenced who could be trusted when survival depended upon cooperation.

The lives of coalition members possessed extraordinary value.

The lives of competitors often did not.

This pattern appears repeatedly throughout human history.

Men willingly sacrificed themselves for family, tribe, clan, regiment, or nation while simultaneously fighting, raiding, conquering, or killing members of competing groups.

From a modern perspective this may appear contradictory.

From an evolutionary perspective it is exactly what we should expect.

The same psychological mechanisms that produce self-sacrifice for the in-group can produce indifference, hostility, or violence toward out-groups.

Morality appears to have evolved primarily in the context of coalition survival rather than concern for humanity in the abstract.

It emerged to maximize the survival and success of coalitions.

This is one reason modern moral intuitions can differ so dramatically from those of our ancestors.

Civilization transformed the environment in which moral systems operated.

Agriculture produced surplus.

Surplus produced specialization.

Specialization allowed increasing numbers of people to live without hunting, fighting, or directly defending the group.

The responsibility for violence became concentrated in a shrinking percentage of the population.

Most people became consumers of security rather than providers of it.

As this occurred, moral frameworks increasingly expanded beyond the immediate coalition.

Religious traditions began extending moral concern beyond kinship groups.

Empires created broader identities encompassing multiple tribes and peoples.

Modern states extended legal protections to millions of strangers.

Industrial societies eventually produced moral systems that increasingly emphasized universal human rights, universal human dignity, and universal moral concern.

Whether this development represents moral progress, moral divergence, or some combination of both is a question reasonable people may debate.

What matters here is that these moral systems emerged under conditions radically different from those that shaped human evolution.

For the first time in history, large numbers of people could advocate moral principles without personally confronting many of the realities those principles depended upon others to manage.

The farmer no longer defended the frontier.

The merchant no longer stood watch against raids.

The professor no longer hunted for food.

The citizen no longer fought most wars.

Specialists performed these functions on behalf of society.

This distance from the realities of coalition competition does not necessarily make modern moral systems wrong.

But it does make them historically unusual.

And it creates the possibility that individuals exposed to war may experience profound conflict between modern moral expectations and realities that would have been familiar to their ancestors.

This possibility leads directly to a different interpretation of combat psychology.

Perhaps the central issue is not that human beings possess a universal resistance to killing.

Perhaps the central issue is that many people enter combat carrying moral expectations shaped by the protected world from which they came, only to be confronted by realities that have always belonged to the protector’s role.

If so, psychological injury may arise when the moral assumptions of the protected world collide with the realities of the warrior’s role.

Human beings do not enter combat carrying identical moral frameworks.

They enter combat carrying expectations shaped by family, religion, education, peers, institutions, and culture.

Psychological injury emerges when reality collides with those expectations.

A soldier who kills while defending his comrades.

A soldier who accidentally kills civilians.

A soldier who witnesses atrocities.

A soldier who feels betrayed by leaders.

A soldier who concludes that his sacrifices served no legitimate purpose.

All may experience similar symptoms.

But the psychological mechanisms involved are radically different.

The act itself cannot explain the difference.

Meaning can.

Conclusion

The greatest mistake in combat psychology was treating violence as the problem.

Violence is ancient.

Fear is ancient.

Coalitionary conflict is ancient.

What changes across societies and historical periods is morality.

Marshall and Grossman interpreted combat through the lens of civilization.

They mistook historically recent moral intuitions for universal features of human nature.

An evolutionary perspective suggests a different interpretation.

Human beings evolved in a world where hunting, defense, coalition loyalty, and competition over resources were ordinary features of life.

Our moral systems evolved in response to those realities.

Civilization changed those realities.

It changed morality.

And when modern moral frameworks collide with the realities of war, psychological injury can emerge.

The future of combat psychology lies not in asking why violence traumatizes people.

The better question is this:

Why does a particular experience violate a particular person’s moral expectations?

Until we answer that question, we will continue treating symptoms while misunderstanding causes.

References

Boehm, C. (1999). Hierarchy in the Forest: The Evolution of Egalitarian Behavior.

Chambers, J. W. II. (2003). S. L. A. Marshall’s Men Against Fire: New Evidence Regarding Fire Ratios. Parameters, 33(4), 113–121.

Ferguson, C. J. (2015). Do Angry Birds Make for Angry Children? A Meta-Analysis of Video Game Influences on Children’s and Adolescents’ Aggression, Mental Health, Prosocial Behavior, and Academic Performance.

Grossman, D. (1995). On Killing: The Psychological Cost of Learning to Kill in War and Society.

Marshall, S. L. A. (1947). Men Against Fire: The Problem of Battle Command.

Mitani, J. C., Watts, D. P., & Amsler, S. J. (2010). Lethal Intergroup Aggression Leads to Territorial Expansion in Wild Chimpanzees. Current Biology, 20(12), R507–R508.

Spiller, R. J. (1988). S.L.A. Marshall and the Ratio of Fire. RUSI Journal, 133(4), 63–71.

Wilson, M. L., Boesch, C., Fruth, B., et al. (2014). Lethal Aggression in Pan Is Better Explained by Adaptive Strategies Than Human Impacts. Nature, 513, 414–417.

Wrangham, R. W. (1999). Evolution of Coalitionary Killing. American Journal of Physical Anthropology, 110(S29), 1–30.