Why Do Humans Go to War? Lessons from the March 2026 U.S.-Iran War

Why Do Humans Go to War?

Thinking across philosophy, biology, and political science through the March 2026 U.S.-Iran war

On March 5, 2026, AP and Reuters reported that a coordinated U.S.-Israeli strike over the weekend killed Iran's Supreme Leader Ali Khamenei and other senior figures, and that the crisis had already expanded into a wider regional war. Reuters described it as day six of the "U.S.-Iran war" or a "U.S.-Israeli campaign against Iran." Casualty figures were fluid: one Reuters tally cited at least 1,230 deaths in Iran, including 175 girls and school staff killed at an elementary school in Minab, while another report carried a state-media-based count of 1,045. Reuters also noted these wartime numbers were not independently verified. Yet some facts were already clear: WHO had confirmed attacks on 13 medical facilities in Iran, at least nine vessels were hit in the Gulf, disruption in the Strait of Hormuz was affecting roughly one-fifth of global oil and LNG flows, and U.S. forces had already reported six service members killed. Numbers can shift; absent lives do not return.

War does not happen only at the front. It unfolds in domestic opinion, alliance politics, logistics, markets, information systems, and competing languages of justice. A Reuters/Ipsos poll closed on March 1 found 27% support for U.S. strikes on Iran, 43% opposition, and 56% saying President Trump was too eager to use military force. Before war is a technology of killing enemies, it is also a politics of manufacturing consent among allies and citizens.

My answer is this: humans wage war because we are both a species that retains territorial and coalition psychology and an animal that can massively amplify those impulses through states, myths, laws, propaganda, and technology. Evolution gave us group-making capacity, but groups split easily into "us" and "them." In an anarchic international system there is no final judge, trust is partial, information is asymmetric, leaders have incentives to misrepresent, and domestic politics punishes compromise. So war is not just instinct, not just madness, and not just cold rationality. It becomes likely when evolved tribal mindsets enter an anarchical state order and are fed by fear, deception, and powerful tools. At the same time, humans also possess institutions, empathy, reason, and shared goals that can restrain violence. War is a human possibility, not a destiny.

1. Why Humans Fight as Biological Beings

Evolution did not optimize for happiness or meaning; it selected tendencies that improved survival and reproduction in ancestral environments. Recent reviews in evolutionary psychology organize the argument that coalitionary aggression could have expanded access to contested resources and mating opportunities. Related work suggests humans may have context-sensitive heuristics for coalitionary aggression, distinguishing defensive from offensive situations. Parochial altruism theory likewise examines the coevolution of strong in-group cooperation with hostility toward out-groups. We are not only isolated individuals; we are also shaped as group animals ready to defend insiders and monitor outsiders.

Chimpanzee evidence highlights the harsh edge of this logic. A 2025 PNAS-related discussion reported that the Ngogo community in Uganda killed at least 21 individuals from neighboring groups, expanded territory by 22%, then saw female births rise from 15 to 37 over three years while early mortality fell from 41% to 8%. In evolutionary terms, there are conditions where violence appears to "pay." If resources are scarce and boundaries matter directly for survival, killing can correlate with reproductive success.

But that does not mean humans are biologically condemned to war. Bonobo research indicates different possibilities: long-run field data show how coalition structure, especially female alliances, can transform dominance outcomes. The UNESCO-linked Seville Statement similarly concludes that biology does not doom humanity to war. Biology supplies conditions and capacities, not a verdict.

2. How Human Psychology Produces Enemies

Social psychology explains this with uncomfortable clarity. In social identity theory, people seek positive self-regard through group membership, and group value is often evaluated comparatively. Even without overt resource conflict, pressures emerge to create status distinctions: "our group is better." Minimal-group experiments show that in-group favoritism can arise from very thin categorization.

Threat framing accelerates this mechanism. Neuroscience and intergroup-bias research suggest that when out-groups are framed as realistic or symbolic threats, people become more ethnocentric, less empathic, more prone to dehumanization, and more accepting of punitive or aggressive behavior. Mortality salience can intensify identity fusion and prejudice toward value-dissimilar groups. War generates deaths; deaths harden group psychology; hardened psychology makes further violence easier.

Language is decisive here. Dehumanization works by re-describing people as vermin, machines, contamination, or abstract targets, reducing moral inhibition. Re-humanization does the opposite by restoring personal detail, names, and individual stories. Evidence on superordinate goals and dual identity frameworks suggests that cooperation can be designed when groups can remain themselves while also belonging to a larger "we." If war has a psychological architecture, peace can have one too.

3. Why States Fight Even When War Is Costly

Classical political thought already saw the structural problem: beyond the state, there is no sovereign authority above states. Security dilemma logic shows how defensive moves by one state can look offensive to another, producing mutual fear spirals even when neither side seeks conquest.

But if war is costly, why not bargain? Rationalist war theory emphasizes that war is ex post inefficient: if both sides bear costs, there should exist cheaper settlements in principle. Persistent war often comes from three mechanisms: private information and incentives to bluff, commitment problems (today's promise may not hold after tomorrow's power shift), and issues that appear indivisible or become politically non-divisible due to domestic institutions and audience costs.

Seen this way, the U.S.-Iran war cannot be reduced to one moral slogan. What we observe is a network cascade: strikes on Iranian territory, retaliatory attacks on Israel and regional bases, spillover into Lebanon and the Gulf, damage to health infrastructure, maritime disruption, and energy-market shocks. War becomes a web involving allies, proxies, shipping lanes, domestic publics, and credibility traps.

4. What History and Data Show

Global conflict datasets indicate elevated contemporary violence: high counts of state-based conflicts, a notable number crossing war-intensity thresholds, and vast displacement levels. At the same time, long-horizon data suggest that some periods of the twentieth century were even more lethal in battle deaths. The lesson is mixed: humanity has not fully progressed, but neither has it remained static. Large interstate total war is less frequent, while proxy conflict, civilian vulnerability, precision strike systems, and information warfare have become more central.

Military spending and nuclear posture reinforce this paradox. Global military expenditure remains at record levels, and nuclear arsenals persist with significant portions in high readiness. Human beings publicly praise peace while continuously investing in preparations for catastrophe.

5. What Philosophers Saw

Thucydides distinguished stated pretexts from deeper causes, especially fear generated by power transitions. Hobbes warned that in the absence of a common authority, conflict tendencies intensify, yet he also argued reason can identify peace as good and seek institutions to secure it. Rousseau observed that wars are fought not by abstract "humanity" but by political bodies, with ordinary people pulled into state-level enmity.

Plato and Aristotle linked external disorder to internal disorder: political injustice and moral imbalance inside a community are not separate from violence outside it. Kant sought perpetual peace not through sentiment alone but through institutional design: accountable republican government, federation-like cooperation among free states, and legal frameworks that reduce incentives for reckless war. He also warned that a single world state could become universal despotism.

Simone Weil saw force as something that turns persons into things and deforms both victim and wielder. Hannah Arendt distinguished power from violence, arguing that violence is an instrument and cannot substitute for durable legitimacy. Einstein's 1932 exchange with Freud asked whether humanity could redirect aggression away from destruction; in the age of AI, drones, and algorithmic propaganda, that question is more urgent, not less.

6. Would Universal Strength Create Peace?

The intuition that if everyone were heavily armed, no one would dare attack, captures a part of deterrence logic. But deterrence is not the same as healthy peace. It can freeze major war while trapping societies in permanent fear, error risk, accidental escalation, and expensive arms races. A world saturated with high-readiness destructive capacity is less a solved condition than a suspended emergency.

7. How Should We Live Anyway?

If war has many layers, peace must be built in many layers too. Biology identifies capacities for aggression; psychology maps triggers and buffers; political science reveals bargaining failures and institutional fixes; philosophy offers language to orient action. Hope is not naive optimism that people are naturally kind. Hope is institutional and narrative work that makes cruelty harder to organize.

Practical steps follow: do not collapse the dead into anonymous statistics; resist dehumanizing labels; expand monitoring and verification mechanisms across borders; strengthen hotlines, inspections, parliamentary oversight, and media scrutiny; and cultivate dual identity so people can be both loyal citizens and members of humanity.

In the AI age, the central question is not only targeting precision but moral range. Technology will sharpen means. The decisive variable is whether conscience expands with capability.

8. Conclusion

Why do humans wage war? Because we are biological. But not only biological. Because we are group-bound, state-organized, fearful, distrustful, meaning-seeking, and often tempted to monopolize justice.

And one more truth: before humans wage war, they usually need stories that justify war. So preventing war requires not only changing weapons and doctrines, but changing stories. Replace narratives that objectify enemies with narratives that preserve names, faces, and irreducible human status.

Hope is not a sweet prediction that things will work out. Hope is the repeated decision not to turn others into things. The planet is small and human life is short. That is precisely why our task is to build orders that let others live, rather than systems optimized to erase them.

I am also placing related latest reports below for reference.