International humanitarian law (IHL) is often described as a triumph of principle over pragmatism; a set of rules meant to restrain war even when all else is breaking down. After all, the Geneva Conventions (1949) promise protection “in all circumstances” not just when an adversary behaves well in return. In practice, though, the logic of reciprocity continues to shape the ways States fight, negotiate, and justify restraint.

Why does reciprocity (the idea that restraint should be met with restraint and violation with reprisal) refuse to die? Why do combatants continue to expect fairness in war even when the law insists that compliance should be unconditional? This question lies at the heart of my book The Persistence of Reciprocity in International Humanitarian Law. Reciprocity endures as the hidden grammar of compliance and legitimacy in warfare despite more than a century of legal reform seeking to purge it from IHL.

Suspicious Origins: The Rejection of Reciprocity

From its modern beginnings IHL has treated reciprocity with deep suspicion. In the nineteenth century, the founders of the International Committee of the Red Cross (ICRC) worried that allowing the protection of wounded soldiers or prisoners to depend on an enemy’s conduct would corrupt the moral purpose of the law.

Article 1 common to all four of the Geneva Conventions (1949) embeds this logic: States undertake to respect and ensure respect for the Conventions “in all circumstances.” In theory, compliance should not depend on the other side’s behavior. The humanitarian ethos demands one-sided commitment. You comply with the Conventions because compliance is the right thing to do, and not because you expect compliance in return.

But this moral clarity was born of historical struggle. Early humanitarian rules emerged in a work that took reciprocity for granted. The Lieber Code (1863), one of the first codified law of war instruments, justified restraint by reference to the expectation of mutual benefit. Treating prisoners humanely encouraged the enemy to do the same. Nineteenth century European military manuals routinely invoked reciprocal obligation as the conversion of restraint.

However, by the twentieth century the horrors of industrialized total warfare and the Holocaust prompted reforms to break from that logic. They feared that reciprocity bred a moral equivalence that could justify cruelty on the grounds that “the other side started it.” As such, the Geneva Conventions redefined humanitarianism as categorical, not conditional. States were to protect even those who violated the law. In the new version, reciprocity was a temptation to be resisted.

But the story did not end there.

The Shadow of Reciprocity

In practice, reciprocity never disappeared. Even as the Conventions outlawed reprisal against protected persons, governments continued to invoke reciprocity to justify compliance and to explain its breakdown.

Consider the Protocols Additional to the Geneva Conventions (1977), which expanded protections for civilians and combatants in civil wars. Many Western States hesitated to ratify the Additional Protocols, fearing that non-State actors would not reciprocate. For example, both the United States and the United Kingdom argued that extending prisoner of war status to irregular fighters without any reciprocal guarantees would undermine both discipline and deterrence. Put another way, they worried that if unilaterally offered, humanitarianism would not be sustainable.

Similarly, in contemporary armed conflict, States still frame IHL compliance as a two-way moral exchange. Ukraine emphasizes that its treatment of Russian prisoners demonstrates its commitment to international norms and that it expects the same. Israel and Hamas both invoke claims of fairness and violation, however differently interpreted. Even the United States in its struggle with non-State actors has oscillated between asserting unconditional adherence and invoking reciprocal breakdowns to explain lapses in compliance with IHL.

The persistence of these arguments reveals something important. Reciprocity is not simply a legal rule to be banned or endorsed. It is a social logic that continues to shape how combatants understand fairness, legitimacy, and self-restraint.

Reciprocity as a Social Logic

International relations scholar Robert Keohane famously distinguished between specific and diffuse reciprocity. Specific reciprocity describes immediate, tit-for-tat exchange: “I comply because you comply.” Diffuse reciprocity involves a broader expectation that cooperative behavior will be rewarded over time; trust builds across repeated interactions.

IHL reformers rejected the first but could not escape the second. When States comply with humanitarian norms they often do so not from pure altruism, but because they believe others (whether adversaries, allies, or the international community) will respond with respect, legitimacy, or restraint in return.

This broader sense of reciprocity does not degrade humanitarianism but sustains it. It connects legal restraint to the moral economy of war and to shared understandings of fairness and recognition. When soldiers are told to treat prisoners of war humanely “because that’s what makes us different,” they are not merely appealing to pure duty, but to reciprocal identity: we act this way because they (or the world) will see us as lawful, civilized, and worthy of the same.

Thus, even when legal texts deny reciprocity, the practice of humanitarianism in warfare depends on it. It is the invisible link between legality and legitimacy.

The Persistence of Reciprocity

I argue in the book that reciprocity persists in IHL for three reasons.

First, reciprocity links law to compliance. Rules gain traction not just through moral appeal but through mutual expectations. States follow IHL not only because it is the right thing to do but because they anticipate benefits (reputational, strategic, or reciprocal) from doing so. Even when formal reciprocity is outlawed or not required, compliance mechanisms rely on mutual recognition of restraint.

Second, reciprocity embeds fairness in law’s moral fabric. The language of humanitarianism still borrows from ideas of proportionality and equality of treatment. To insist that a wounded soldier deserves care “regardless of nationality” is itself a statement of reciprocal fairness. Each human life is valued equally.

Third, reciprocity connects law to legitimacy. States often justify military restraint through reciprocal rhetoric: “we uphold the norms because they uphold us.” The power of IHL depends less on coercion than on the belief that others (peers, publics, or adversaries) will respond in kind.

In this sense, reciprocity operates not only between warring parties but also between States and the international community. When a government complies with humanitarian norms, it expects acknowledgement via legitimacy, support, or moral authority. That expectation of recognition is itself a form of diffuse reciprocity.

The Double Life of Reciprocity

The persistence of reciprocity creates a paradox for IHL. It is both a threat to and a condition of the law. Reciprocity can justify vengeance and collective punishment when abused. But when understood as fairness or recognition it anchors restraint in a shared moral logic.

This duality explains why reciprocity keep resurfacing, from the Vietnam War to Guantánamo Bay to Ukraine. Each time law confronts the reality of war, reciprocity reemerges as the language through which States explain what went wrong or what must be defended.

For example, the U.S. military’s internal debates over detainee treatment in the early 2000s were framed partly in reciprocal terms. Some argued that adhering to the standards of IHL even for “unlawful combatants” would strengthen America’s reciprocal claims should its own soldiers be captured. Others contended that reciprocity was impossible against terrorist groups that ignored the law altogether. Both sides, however, assumed reciprocity mattered. It remained the grammar of moral reasoning in war.

The Human Face of Reciprocity

The persistence of reciprocity is not merely institutional but human. Soldiers, diplomats, and civilians all think in reciprocal terms. After all, fairness is a deep human instinct. Even young children understand reciprocity before they can articulate justice.

This instinct manifests itself in powerful ways during times of war through truces to recover the wounded, gestures of restraint towards captured enemies, and the expectation that mercy will be returned. These acts are not always altruistic. They are pragmatic expressions of mutual recognition. But that recognition is precisely what makes humanitarianism in time of war possible.

This insight complicates the standard narrative that law and reciprocity are at odds. Law requires a foundation in social meaning and reciprocity provides it. It transforms abstract duty into a lived practice of fairness.

Why it Matters

Recognizing the persistence of reciprocity in IHL does not mean surrendering humanitarian ideals to pragmatism. It means acknowledging the conditions under which these ideals survive.

If law depends on mutual recognition, then the real danger lies not in reciprocity, but in its collapse. When one side sees the other as beyond the bounds of reciprocal obligation, as an enemy undeserving of recognition, then the humanitarian project of IHL fails. The most serious violations of IHL often occur when reciprocity is denied altogether such as when adversaries are dehumanized, excluded from protection, or treated as unworthy of mutual restraint.

To preserve IHL, then, we must understand reciprocity as the mechanism that translated moral principle into practice and not as the enemy of morality.

Conclusion: Rethinking Reciprocity

Reciprocity refuses to go away because it captures something fundamental about how we understand justice, even in times of war. It endures, not as a relic of primitive exchange but as a form of mutual recognition that gives IHL its practical force.

In my next post on this topic, I’ll explore how reciprocity can be reimagined as recognition rather than retaliation. By distinguishing specific, diffuse, strategic, and asymmetric forms of reciprocity, we can see how law, morality, and strategy are intertwined to sustain restraint in an age of asymmetric conflict.

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Bryan Peeler is the Assistant Professor and Associate Head of the Department of Political Science at University of Manitoba.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

 

 

 

 

 

Photo credit: U.S. Army, Army Sgt. David Resnick