Why War?

by Richard Overy

Cover of Why War?
complete 216 pages
History
Added: June 18, 2025 Updated: June 18, 2025

Reading Questions

Is war a part of the human condition, or are human beings normally peaceful?

  • Yes, when war is defined as interspecies violence. For all of human history, humans have engaged in forms of violence for varied reasons.

How does Overy connect the four academic disciplines to his four “orbits” of explanation: resources, belief, power, and security?

  • The thread he pulls between academic disciplines and his four “orbits” is weak, but there. Resources are a continuation of biology and ecology, while belief and power are a continuation of anthropology and psychology. Security is a mix of all the fields presented.

What is a monocausal explanation? Why are such explanations attractive, and why can they be dangerous?

  • A monocausal explanation links an effect, in this book, war, to a singular cause. They are attractive because they are simple and easy to work with, while not requiring wisdom (the ability to hold multiple opposing views as true). They are dangerous because the evidence points to them never being true in the case of war, which could lead to unintended wars or mispredictions.

Is Overy pessimistic, or realistic?

  • Overy is an evidence-based realist. He doesn’t extend his ideas significantly past what is available in evidence, but looks at the data objectively to draw his conclusions.

Online Description

An Economist Best Book of 2024 Why has war been such a consistent presence throughout the human past? A leading historian explains, drawing on rich examples and keen insight. Richard Overy is not the first scholar to take up the title question. In 1931, at the request of the League of Nations, Albert Einstein asked Sigmund Freud to collaborate on a short work examining whether there was “a way of delivering mankind from the menace of war.” Published the next year as a pamphlet entitled Why War?, it conveyed Freud’s conclusion that the “death drive” made any deliverance impossible—the psychological impulse to destruction was universal in the animal kingdom. The global wars of the later 1930s and 1940s seemed ample evidence of the dismal conclusion. A preeminent historian of those wars, Overy brings vast knowledge to the title question and years of experience unraveling the knotted motivations of war. His approach is to separate the major drivers and motivations, and consider the ways each has contributed to organized conflict. They range from the impulses embedded in human biology and psychology, to the incentives to conflict developed through cultural evolution, to competition for resources—conflicts stirred by the passions of belief, the effects of ecological stresses, the drive for power in leaders and nations, and the search for security. The discussions show remarkable range, delving deep into the Neolithic past, through the twentieth-century world wars, and up to the current conflict in Ukraine. The examples are absorbing, from the Roman Empire’s voracious appetite for resources to the impulse to power evident in Alexander the Great, Napoleon, and Hitler. The conclusion is not hopeful, but Overy’s book is a gift to readers: a compact, judicious, engrossing examination of a fundamental question.

🔫 Author Background

🔍 Author’s Main Issue / Thesis

  • Overy argues that what causes war is multifactorial, and no one cause can ever be used to predict war, or, arguably, determine the reason a war started post hoc. While he argues that there is little evidence of the availability of ancient hominids to support ideas of a biological root for aggression/war, he focuses most on modern conflicts as they relate to Resources, Belief, Power, and Security to show there is no one reason for any given conflict.

📒 Sections

Introduction

  • The book is aimed at anyone who wants to learn more about modern research on “Why War?” by examining multiple assumptions and arguments related to war.
  • Freud argued that humans have a “death drive”, which is an impulse to destroy things.
  • The author breaks the problem into two areas of research: the Human Sciences (biology, psychology, anthropology, and ecology), historians, and social/political scientists. The first is viewed as passive since humans are driven by their environment, while the second is viewed as proactive because humans serve as conscious agents.
  • “Warfare is used in this broader sense of collective, purposive, lethal, intergroup violence, whether raids, or ambushes, or skirmishes, or ritual violence, or the more familiar pitched battles of the historic period.”
  • This book examines why wars happen, not whether mankind has become less violent, or why individuals show aggression.

Key Points

  • 1) Biology

    • In this chapter, Overy argues that one factor that can influence why humans go to War is possibly genetic due to increased reproductive success. Still, without evidence from early humans, he argues that knowing is impossible. Biology views war as genetic.
    • Since Darwin created the idea of “the struggle for survival,” researchers have attempted to determine if aggression/war is genetic and results from human evolution.
    • Germany took this idea to the extreme during WWII, arguing that war would enable the superior German race to persist, but they were not alone; multiple people have argued that war produces more fit humans.
      • One counter to post WWI was the significant loss of fit young men in The War.
    • Researchers have attempted to use higher-level primates to explore the genetic roots of aggression, arguing that general primate violence indicates that aggression is biological.
      • The counter is that primates and humans have evolved separately for millions of years, and primates are not valid surrogates for humans, even hominids.
    • Another argument is that an adaptation for coalitional violence against other humans supported ongoing reproductive success. This was broken down into two categories.
        1. Inclusive fitness, the idea that genetically related kin all contributed to the kin group’s genetic reproduction, so it was beneficial to defend the kin group.
        1. Competitive exclusion, the idea that competition over resources drove kin groups to eliminate or reduce neighbors.
    • Whatever the driving biological force, males must still be convinced to risk their lives. This can be done by punishing “free riders” or through the idea of “parochial altruism”, which is the idea that males will accept risk to support their group to ensure continued survival.
    • While there are some historic examples of Women fighting, biology generally looks at the problem of War as males using aggression to show biological advantage, and females developing to flee or submit to violence. Additinally, females may have promoted male aggression by selecting the mates they believe could best defend them.
    • Conflict as a means of inclusive fitness aligns with evolutionary theory, but remains speculative because there is no way to gather evidence from early human communities.

  • 2) Psychology

    • In chapter two, the author looks at the possible psychological origins of War (most lack evidence), and finds that group learned aggression and the reduction in empathy for out-groups may play a role. Psychology views war as a learned behavior by the individual.
    • Presents Freud’s idea of the Oedipus complex, or the idea that an individual’s traits can be linked to their earliest interactions with their mother. The idea is that a mother removing her breast from a baby creates aggression and primes them for war in adulthood.
      • No evidence at all
    • Other researchers argued that the war can serve as therapy for the aggression learned in childhood from the mother, because it removes the guilt of violence while allowing the individual to enact it. Additionally, the enemy can be viewed as a surrogate for the father, which, per the Oedipal drive, all males want to kill.
      • Again no evidence
    • Psychology argues that aggression is a learned response to frustration or fear, not a biological imperative.
    • The idea of learned individual aggression extends to learned group aggression as well. Male groups that react aggressively and are rewarded learn that future aggression will also result in rewards.
    • The Vikings and Spartans are examples of learned group aggression at a societal level.
    • Much like biology, psychology offers little evidence for any one idea because the minds of humans from a thousand years ago can not be known.
    • Some experiments have been done with children, but they are mostly dismissed due to children being raised in cultures that reinforce male/female stereotypes.
    • Evolutionary psychology can’t explain why a war starts or who is defined as an enemy, but social psychology does have theories on how enemies are defined.
      • Evidence suggests that even pre-state communities had ideas of in-groups and out-groups, leading to out-groups being viewed as the enemy.
      • This extends into the modern era with the German idea of the Volk.
    • However, when an enemy is identified, the state leads to a reduction or the elimination of empathy for the enemy. This can be seen even years after a conflict. For example, in post-WWII Germany, it took a generation to feel empathy for the suffering of the Jews.

  • 3) Anthropology

    • The view of warfare from anthropology looks at the problem as a cultural evolution but can’t identify why a war starts; it is just the human norms that prime a culture for war. Additionally, with warfare being a universal human condition, it may support the ideas of biology and psychology as war being a universal human driver. Anthropology views war as learned culturally.
    • Margaret Mead argued that warfare was a human invention and could be uninvented.
      • If this is true, when was it invented, and why?
    • There are four types of evidence for conflict in our prehistoric past (all are open to interpretation)
      • Skeletal trauma
      • Iconography
      • Fortified settlements
      • Weapons
    • This community debates over what warfare is; members who believe warfare is a recent invention tend to link the activity to the development of states. The other side argues that community violence, such as raids and ambushes, should also be viewed as warfare, allowing for a significantly earlier invention of warfare.
    • Early anthropologists viewed human ancestors as ‘Noble Savages’, but modern research has made it difficult to sustain this idea. (peaceful nomads)
    • Evidence for human warfare goes back ~20,000 years. The conditions existed further back, but the evidence most likely doesn’t exist.
    • The evidence points to some tribal people as egalitarian (every adult male fought), and some having warrior elite like the Spartans.
      • When elite warriors emerged, it varied between cultures.
    • Anthropologists now argue that warfare was a cultural adaptation.
      • Increased resources
      • Social privileges (initiation rites, revenge, sacrifice)
      • The culture of warfare was passed from generation to generation until it became part of the culture.
    • “Cultural variability dictates how warfare might be regarded in different times and contexts, while material or immaterial motives for war are still necessary for warfare to happen. But cultures of war are universal, just another invention which suggests that biology and psychology might still have something to contribute alongside culture in explaining a phenomenon that is more than just another invention.”

  • 4) Ecology

    • Ecology looks at the problem of Why War occurs through the lens of what human population a given area can support. It argues that regions with few natural resources drive conflict; however, there is little evidence for this argument. Ecology views war as an environmental outcome.
    • Ernst Haeckel suggests that when human populations outgrow the carrying capacity of land, they can turn to warfare to adjust the population levels.
    • Der Lebensraum argued that a significant reason people battle is for space.
      • Hitler used the term Lebensraum in his arguments for German expansion, so it is rarely used today.
    • While there is little evidence from prehistoric/proto-state humans, it is hard to believe that carrying capacity did not drive conflict.
    • Premodern groups go to war when the population outstrips the carrying capacity.
    • The most extreme evidence of a carrying capacity crisis is cannibalism.
      • Maybe due to other factors, such as religion.
    • The community is still debating whether a shortage of living space triggers warfare, versus culture or human objectives.
      • Broadly accepted that territorial trespass often leads to violence.
    • WWII Germany was a prime example of living space leading to war, since Hitler spoke and wrote about the idea as a primary driver for the conflict. Italy and Japan used the same argument during the war to justify aggression.
      • It could just be a cover for other motives/propaganda.
      • It is a failed idea in the modern world, since trade and farming improvements have significantly increased carrying capacity. Still relevant in underdeveloped states.
    • Climate change is another ecological pressure that may lead to increased warfare by reducing the carrying capacity of land.
      • Drought and extreme rainfall lead to crop disruption and reduced carrying capacity.
    • There is not much evidence for any of the ecological ideas. Still, it may be the case that increased ecological pressure encourages one of the other factors to tip the scales towards war.

  • 5) Resources

    • The book’s second part looks at the drivers for war based on a school of science. The idea is that humans go to war for resources to expand populations or gain power. ** The need for resources drives countries to war.**
    • The drive for resources is separate from ecological pressure, because resources are viewed as things that give power beyond the necessities for life.
      • I’m early in, but I can’t see how this differs from ecology. No one needs to steal to live, but humans do to increase the land’s carrying capacity.
    • The Marxist-Leninist view is that all conflict is based on capitalism, so the only way to stop it is to kill the bourgeois and share resources equally.
      • This view also allows for the oppressed to wage war against the oppressor.
    • Almost all conflicts have resulted in some material gain, so it is hard to argue that it isn’t a factor or the primary factor.
    • The link between slavery and warfare is hard to establish because slaves are generally taken after the initial violence is complete.
      • Weak argument to me, while dehumanizing slaves is viewed as a resource, the author has no problem talking about the wars potentially waged for oil.
    • In many cases, economic gain in war was a bonus but not the principal cause.
    • A need/want drives resource and climate wars for increased resource access.
    • Most resources are abundant enough not to require resource wars, but the limited resources that drive war occur in regions with political/ethnic tension.
      • A pauper sitting on a mountain of gold. Extraction-based economies lead to poor institutions, leading to poor government/outcomes.
    • Resources can be used to continue the war, by selling off resources, actors can gain additional income for weapons and fighters.
    • Oil is a fixed asset (vs lootable), so it may drive additional wars in the future as supply is constrained.
    • Value is a human construct, so wars are linked directly to resources, psychology, and anthropology.

  • 6) Belief

    • Belief looks at all forms of religion as drivers of war, arguing that a secular world view can not be applied to counter the argument, because religions are deeply held beliefs that can drive members to extremes. Belief drives war to defend and promote religions
    • Belief has not driven all wars, but has been the context for many throughout human history.
    • Christianity and Islam are the modern belief drivers of war, but beliefs as drivers of war go back further in history than modern religions.
    • The commonly assumed belief is used as an opium for the masses to support going to war, but it is not the major reason for war. This point is easy to establish with a secular world view, but hard to maintain as a religious person.
      • “However exotic or fantastic many beliefs seem to a modern audience, it is necessary to understand them from within, in what anthropologists define as “emic” meaning, rather than through evaluation of external, universal, or “etic” terms. Attached to many such beliefs is a commitment to warlike violence that cannot be understood separate from the faith, or belief, or ideas that generate it. Without recognizing the power of belief in mobilizing and permitting violence, explanations for many kinds of warfare will be incomplete or poorly understood.”
    • It is a paradox that Christianity was founded on the idea of loving your neighbor, but has endorsed so much warfare.

  • 7) Power

    • Power looks at war as a means to gain and maintain power, either at the state or individual level, while it is hard to justify that the sole reason for war is a potent motivator for conflict. Power drives war to gain power.
    • War and the threat of war have been used in various forms to gain “compulsory power.”
    • Small egalitarian communities didn’t have an idea of power, because they could move.
    • Power through war can come about in two different ways:
        1. Power of external communities
        1. Internal power gained by the prestige of war
    • In Roman culture, power and war were central. Consuls had to explain why they didn’t go to war, instead of justifying war in the first place.
    • Another example of power is “hubristic power”, or the power associated with a single person like Khan, Hitler, Napoleon, or Alexander.
    • Hubristic power, generally, allows a single person to determine if a country goes to work, reinforced by the governmental system they created.
    • Hubristic power leads to “destructive leadership.” Where the leader wages cynical, self-defeating wars in an attempt to gain/maintain power.
      • Power is corrupting
    • Great powers attempt to balance power between equal states, but can be upset by up-and-coming powers.
      • Hard to research because power isn’t a measurable metric
    • Thucydides Trap is the idea that war is hard to avoid for two countries competing for hegemony.
      • US vs China
    • Power Transition theory argues that the closer a rising power is to the current hegemony, the more likely war is.
    • The new multipolar world has academics debating whether the risk of war is now greater or if the Great Powers can find a new balance to enable peace.
      • If states are rational actors, balance should be achieved because all parties are nuclear powers.
    • Power is hard to use to explain the cause for war, because it is a means that can be used short of war or in war.
    • War for only power is hard to rationalize, but mixed with all other means presented in this text, the whole could justify the means.
      • Outside of wars caused by Hubristic power.

  • 8) Security

    • Security looks at war as a means to ensure a state’s and individuals’ security. There have been multiple schools of thought on this topic throughout history, but hard to prove as a cause for war with current evidence. Security justifies war, Maslow.
    • Hobbes’ view of human nature, that all humans are self-interested and fearful of death, leads to war. It is human nature to protect oneself and the person’s / community’s security.
    • Security can be maintained through strong defenses or offensive action to degrade enemies.
    • The modern era has led to establishing frontier zones, which provide buffers for the actual state from its neighbors.
      • This further led to the establishment of fixed state boundaries.
      • Frontier has recently gone out of favor as war has expanded to include aircraft and missiles.
    • Security Studies is a field that researches the causes of war and how they might be prevented.
    • Championed by Kissinger, realism is the idea that state survival is key by any means necessary, and states survive based on their power, which enables their security.
      • One idea related to realism is deterrence, or the display that a state has enough power and willpower to retaliate against any aggression, generating a negative ROI for the attacker. It is a rational actor-dependent theory.
    • Realists have broken into two camps:
        1. Offensive realists believe a country must always be ready to go to war with any country.
        1. Defensive realists believe a defensive military and cooperation produce the greatest results.
    • Both create a paradox, because they can’t explain what happens when a realist fails and states go to war. An offensive might have caused it, and a defense leaves a state in a relatively weaker state to conduct war.
    • The security dilemma, a prominent concept in international relations theory, describes a situation where actions taken by a state to increase its security can inadvertently threaten the security of other states, leading to a cycle of escalating tensions and potentially conflict.
    • Like the other areas, wars for security can be seen throughout all recorded human history, but it is hard to show a singular case for war based on evidence.

Conclusion

  • Theories abound on the causes of war. This reality hastempted the view that warfare cannot be satisfactorily explained because the many theories produce a messy cocktail of ideas rather than the single, coherent answer that Einstein hoped to get from Freud. There is certainly no consensus among those from all the major human sciences who have tried to explain the cause of war over the past century, as the previous chapters have demonstrated.”
  • War is normal because it isn’t a one-off; it has occurred throughout human history.
  • Human violence can not be explained by one factor alone.
    • Humans have adapted to engage in violence, for our genes (survival of the fittest)
    • Humans act with motives such as resources, belief, power, and security.
  • “Warfare viewed through the two levels of explanation, the general context framing the specific motives, can be understood as a mixture of imperatives that have remained remarkably constant over human history, though the mix can vary from case to case.”

☠️ Agree, Disagree, or Suspend

Generally agree that the cause of war is a multiple variable problem, and no one area of reason causes a war. Conditions are set for war through evolution and the environment, and then individuals pursue war for multiple reasons, as highlighted in the book.

🗂 AI Summary

Main Argument:

Richard Overy argues that war is not an inherent or inevitable human condition but rather a deliberate political choice made by leaders and societies based on strategic calculations, perceptions, and ideological justifications. War emerges from specific contexts—political, economic, social, cultural, and technological—and understanding these contexts is essential for comprehending why wars begin and how they might be avoided.

Supporting Points:

1. War as a Political Choice:

  • War results from conscious political decisions rather than mere impulses or inherent aggression.
  • Leaders use war strategically to achieve political goals, secure resources, or assert national prestige.
  • Decisions for war typically involve calculations of risks, benefits, and possible alternatives.

2. Ideological and Cultural Factors:

  • Ideologies significantly influence how societies rationalize conflict, often portraying war as necessary, noble, or morally justified.
  • Cultural narratives around heroism, sacrifice, and national identity can mobilize populations for war.
  • Propaganda shapes perceptions, normalizes violence, and reinforces the notion that conflict is essential or inevitable.

3. Economic and Resource Motivations:

  • Economic competition and the pursuit of resources are central drivers of war, though rarely the sole cause.
  • Industrialization and capitalism intensified competition between states for markets, raw materials, and colonies.
  • Economic interdependence, while sometimes reducing war incentives, can also increase conflict risks due to resource vulnerability.

4. Technological and Military Factors:

  • Technological advancements can alter the calculus of war by providing new offensive or defensive capabilities, sometimes lowering the perceived risks or costs.
  • Militarization and arms races heighten suspicion and fear, making preventive war more likely.
  • The belief in quick or decisive victories due to technological superiority can dangerously underestimate the true costs of war.

5. Misperceptions and Miscalculations:

  • Leaders frequently miscalculate their opponent’s intentions, capabilities, or resolve, leading to unintended escalation.
  • Misjudgments based on incomplete or biased information significantly contribute to war initiation.
  • Historical case studies demonstrate how flawed perceptions have repeatedly led nations into catastrophic conflicts (e.g., World War I and World War II).

6. Historical Context and Precedent:

  • Historical experiences profoundly shape decision-making, with leaders and societies often looking to past wars for lessons, analogies, and justifications.
  • Misapplied historical analogies can create false confidence or fear, encouraging preemptive or preventive wars.
  • Each war, while unique, often reflects enduring patterns of decision-making shaped by historical memory.

Conclusion:

Overy ultimately argues that understanding war requires a multidimensional approach, acknowledging that wars do not simply “break out,” but are systematically chosen within specific contexts and frameworks. Therefore, recognizing these underlying factors and motivations is essential for preventing future conflicts.