Laws of Yesterday’s Wars Symposium – Conclusion

As this symposium draws to a close, one principle emerges as the unifying thread across the societies examined in Volume 4 of The Laws of Yesterday’s Wars: reciprocity. This idea of reciprocal compliance or restraint in conflict is not framed identically in every context, nor does it always operate with perfect symmetry. Yet across cultures as different as ancient Israel, the Hittite Empire, Somali pastoral communities, and Southern African clans, reciprocity is the driving logic behind how communities regulate violence.

Reciprocity Across Cultures

In many ways, reciprocity predates law. Modern international humanitarian law (IHL) reflects the law as written by practitioners of the profession of arms. Of course, these practitioners would not agree (over the centuries) to such rules governing conflict if they weren’t promised support in turn. Studies have shown that this logic of reciprocity weakens sharply as warfare moves from intra-cultural to intercultural and transcultural settings.

In their empirical work, Fazal and Greene demonstrated that belligerents are significantly more likely to comply with restraints on violence when they perceive their adversary as belonging to the same cultural, legal, or civilisational community. Where that shared identity erodes, as in colonial wars, imperial encounters, or conflicts framed against a civilisational “other,” reciprocity collapses, and violence becomes sharper, less restrained, and more instrumental. Their findings suggest that what is often described as the universality of humanitarian restraint is historically contingent: reciprocity functions most effectively where combatants expect future interaction, mutual recognition of the rules governing conflict, and community reintegration. Conversely, reciprocity falters where warfare becomes transcultural, and the enemy is imagined as outside the moral community altogether.

Early on, human groups learned that unrestrained violence leads inexorably to destruction, not only of enemies, but of social bonds, livelihoods, and the delicate systems of cooperation on which survival depends. Reciprocity serves as the countermeasure, a form of restraint built not on abstract principles but on shared expectations, mutual vulnerability, and the knowledge that today’s aggressor may be tomorrow’s victim.

In the Torah, reciprocity manifests in moral duties binding both attacker and defender. Rules governing siege warfare, environmental protection, and proportional use of force assume a moral community in which each party is accountable to God and, by extension, to each other. The protection of fruit trees, for example, is not merely environmental stewardship, but also the preservation of other parties’ future sustenance in the expectation that one’s own lands will be preserved in return.

In the Hittite world, reciprocity takes a legal-diplomatic form. Treaties bind rulers into networks of mutual assistance and shared restraint, enforced through religious sanctions. The gods themselves become guarantors of reciprocity, punishing violations and rewarding compliance. Predictable conduct is not a luxury; it is the glue that holds a sprawling empire and its vassals together.

Among Somali clans, reciprocity is woven into the very fabric of xeer. Protection of women, children, and shepherds is not an abstract humanitarian ideal but a reciprocal guarantee: “we will not harm yours, and you will not harm ours.” Compensation (diya) systems convert violence into enforceable obligations, preventing escalation and preserving the pastoral economy. Crucially, poetry and oral memory reinforce these reciprocal expectations, praising those who keep their word and condemning those who break it.

In Southern Africa, reciprocity emerges through ubuntu, a recognition that one’s humanity is interdependent with the humanity of others. Violence that dishonours another ultimately dishonours oneself. This creates an ethic of measured response, ceremonial restraint, and reconciliation processes designed to restore equilibrium. Even in wartime, the aim is not annihilation but the restoration of harmony, because the victors and the vanquished must continue living side by side.

Truths of Reciprocity

The persistence of reciprocity across such diverse societies reveals several important truths.

First, the impulse to limit war is older and more universal than often recognised. Formal IHL doctrine enshrines obligations without requiring reciprocal compliance, and rightly so, because protections during conflict are owed to persons, not conditioned on an enemy’s good behaviour. Yet historically, reciprocity has been one of the most powerful engines of restraint. It fosters legitimacy, predictability, and incentives to comply, even in theatres where treaty law has limited reach.

Second, reciprocity helps explain why certain norms endure. Communities adhere to restraints not simply because they are moral, but because they are mutually beneficial. They preserve herds, allow harvests, protect clan honour, or avert vendettas. These reciprocal interests create a form of durability that international treaties sometimes struggle to achieve.

Third, reciprocity remains relevant today. Humanitarian negotiators frequently rely on reciprocal commitments, such as pauses in fighting, deconfliction arrangements, or safe passage guarantees, to foster behavioural change in armed groups. Understanding reciprocity’s deep historical roots provides practical insight into how such commitments take hold, and why they fail.

Finally, these findings reinforce the central thesis that underpins The Laws of Yesterday’s Wars: modern humanitarianism is part of a much older human project. Across continents and millennia, societies have developed their own frameworks to restrain violence, grounded in culture, ritual, belief, and practical necessity. Reciprocity is the thread that binds them, a principle as ancient as conflict itself.

As future volumes continue this exploration (with four more volumes in the pipelines and an additional two being planned), reciprocity will remain a lens through which to understand the evolution of restraint, and the many ways communities have sought to humanise war. Studying the past is not an act of nostalgia but an act of preparation. To understand how to build respect for IHL today, we must learn from the reciprocal systems that sustained restraint long before the Geneva Conventions were conceived.

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Dr Samuel White is the Senior Research Fellow in Peace and Security at the National University of Singapore’s Centre for International Law.

The views expressed are those of the authors, 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: Klaus-Peter Simon