Proportionality in War: When Self-Defense Becomes Something Else

A legitimate right to self-defense does not grant unlimited license in how that defense is conducted — proportionality is not optional, and the laws of war apply equally regardless of who started the fight.

Last updated: April 1, 2026

Domain

Philosophy & Rhetoric → Ethics of War → Proportionality, Jus in Bello & Moral Accountability

Position

A country can have every right to go to war and still commit war crimes in how it fights. These are separate legal and moral questions — and collapsing them into one is the single most common trick used to shut down accountability for civilian harm.

International humanitarian law rests on a foundational distinction: jus ad bellum (the right to go to war) and jus in bello (the rules governing conduct within war). These frameworks are deliberately independent. The Geneva Conventions apply equally to all parties regardless of who fired the first shot — precisely so that civilians are protected no matter what. When public discourse treats “they were attacked first” as a blank check for anything that follows, it doesn’t just distort the debate — it undermines the legal architecture that protects civilians in every conflict on earth.

Key Terms

  • Jus ad Bellum: The body of international law governing whether the resort to armed force is justified. Key criteria include just cause (typically self-defense or UN authorization), proportionality of the overall use of force, and last resort. This is the “right to go to war” question.

  • Jus in Bello: The body of international law governing how armed force may be used once a conflict has begun — regardless of which side is “right.” Core principles include distinction (between civilians and combatants), proportionality (civilian harm must not be excessive relative to the concrete military advantage anticipated), and precaution (feasible steps to minimize civilian harm). This is the “rules of war” question.

  • Proportionality (in IHL): The principle that an attack must not cause civilian harm that would be excessive in relation to the concrete and direct military advantage anticipated. This is not a general balancing of “war aims vs. civilian cost” — it is assessed attack by attack, operation by operation.

  • Collective Punishment: The imposition of penalties on an entire population for the actions of individuals — explicitly prohibited under Article 33 of the Fourth Geneva Convention. Sieges, total blockades of food and medicine, and destruction of civilian infrastructure serving no military purpose may constitute collective punishment.

  • The Nuremberg Principles: Established after WWII that “crimes against peace” (starting an aggressive war) and “war crimes” (how a war is conducted) are separate charges. You can be guilty of one and not the other. This separation was not an accident — it was the foundation of the postwar legal order.

Scope

  • Focus: The philosophical and legal framework of proportionality in armed conflict — why the right to self-defense and the conduct of that defense are separate questions, and why conflating them enables atrocity
  • Timeframe: WWII-era origins through contemporary application, with emphasis on the post-October 7, 2023 period
  • What this is NOT about: Adjudicating the Israeli-Palestinian conflict itself, defending Hamas or any armed group, or questioning any nation’s right to self-defense. The framework applies universally — to the U.S. firebombing of Japan, to Russian operations in Ukraine, to Saudi operations in Yemen, and to Israeli operations in Gaza equally.

The Case

1. The Right to Fight Back Does Not Include the Right to Do Anything

The Point: International humanitarian law deliberately separates the justification for war from the conduct of war — because the alternative is a world where whoever is attacked first has unlimited license to kill.

The Evidence:

  • The Geneva Conventions of 1949, ratified by 196 states (universal ratification), apply equally to all parties in a conflict regardless of who is the aggressor. This was a deliberate design choice by the drafters, who understood that making protections contingent on “who started it” would render them meaningless (ICRC Commentary on the Geneva Conventions)
  • The Nuremberg Tribunals prosecuted both “crimes against peace” (waging aggressive war) and “war crimes” (violations of the laws of war) as separate categories. Allied conduct — including the firebombing of Dresden and Tokyo — was debated precisely because the framework requires that even the “right side” follow rules (Nuremberg Charter, 1945)
  • The International Criminal Court’s Rome Statute (2002) codifies this separation: the crime of aggression (starting an illegal war) and war crimes (violating IHL during any war) are distinct crimes with distinct elements. A soldier fighting a defensive war can still commit a war crime; a soldier fighting an aggressive war can still fight lawfully (Rome Statute, Articles 5-8)

The Logic: If the right to self-defense included the right to do anything in that defense, then international humanitarian law would not need to exist. The entire legal architecture — the Geneva Conventions, the Hague Conventions, the Rome Statute — exists precisely because humanity decided after two world wars that “they started it” cannot be the end of the moral conversation. Every army in history that committed atrocities believed its cause was just. That’s exactly why the rules don’t depend on the cause.

Why It Matters: When a commentator says “Country X was attacked first, therefore you can’t criticize their response,” they are not making a legal argument — they are dismantling the legal framework that protects civilians in every conflict on earth. The precedent doesn’t just apply to one war. It applies to all of them.

2. McNamara’s Confession: “We Were Behaving as War Criminals”

The Point: Robert McNamara — the U.S. Secretary of Defense who helped plan the firebombing of Japan — spent his final years publicly admitting that proportionality was violated even in what most Americans consider the most justified war in history, and that the winners’ immunity from prosecution didn’t make the acts moral.

The Evidence:

  • In The Fog of War (2003), McNamara recounted the U.S. firebombing campaign against Japan: 51% of Tokyo destroyed, 99% of Toyama, 58% of Yokohama, 40% of Nagoya — 67 Japanese cities firebombed before the atomic bombs were dropped. Over 100,000 civilians were killed in a single night’s bombing of Tokyo on March 9-10, 1945 (Morris, The Fog of War, 2003)
  • McNamara directly quoted General Curtis LeMay: “If we’d lost the war, we’d all have been prosecuted as war criminals.” McNamara then added: “And I think he’s right. He, and I’d say I, were behaving as war criminals.” This was the U.S. Secretary of Defense acknowledging war crimes committed by his own side in a war that virtually everyone considers justified
  • McNamara posed the question that remains unanswered: “What makes it immoral if you lose and not immoral if you win?” — a direct challenge to the idea that the justice of your cause immunizes your conduct

The Logic: McNamara’s confession is devastating precisely because it comes from an insider — not a critic, not an enemy, but the man who helped plan the operations. His argument is not that WWII was unjust (he believed it was justified) but that the conduct within that just war crossed moral and legal lines. If the United States can fight the most justified war in modern history and still behave as war criminals, then “they were attacked first” is clearly insufficient as a moral defense for how a war is fought.

Why It Matters: McNamara’s framing — Lesson #5: “Proportionality should be a guideline in war” — is not anti-war pacifism. It is a former war planner saying: even when your cause is righteous, you can cross lines that history will judge harshly. The question he poses — what makes an act immoral if you lose but not immoral if you win? — is the entire case for why international humanitarian law must apply equally to all parties.

3. The Pattern: “They Started It” as a Shield Against Accountability

The Point: Throughout modern history, the conflation of “justified war” with “unlimited war” has been used to deflect accountability for civilian harm — and the pattern is recognizable whether the perpetrator is the United States, Russia, Saudi Arabia, or Israel.

The Evidence:

  • The U.S. invasion of Afghanistan after 9/11 was broadly considered justified under international law. Over the subsequent 20 years, the U.S. conducted operations that killed an estimated 70,000+ Afghan and Pakistani civilians, used enhanced interrogation (torture), conducted drone strikes with civilian casualty rates that internal military reviews found unacceptable, and operated extrajudicial detention at Guantánamo Bay — all defended as necessary components of a legitimate self-defense response (Brown University Costs of War, 2021)
  • Russia justified its 2022 invasion of Ukraine partly by claiming self-defense against NATO expansion and an alleged genocide in Donbas (a claim unsupported by evidence). When challenged on civilian casualties, Russia’s response consistently invoked the justice of its cause. The international community correctly rejected this logic — the cause does not justify the conduct (UN General Assembly resolutions, 2022-2025)
  • The Saudi-led coalition’s intervention in Yemen (2015-present), responding to Houthi overthrow of the recognized government, produced what the UN called the world’s worst humanitarian crisis: an estimated 150,000 killed and 227,000 dead from famine and disease. The U.S. and UK continued supplying weapons while citing the coalition’s defensive justification (UN OCHA, 2023)

The Logic: In each case, the pattern is identical: a triggering event provides genuine justification for military action → the responding party escalates beyond any reasonable definition of proportionality → critics raise concerns about civilian harm → defenders invoke the triggering event as a shield against all criticism. The logic is always “but they started it” — as though the initial provocation retroactively authorizes everything that follows. International law exists precisely to break this chain of reasoning.

Why It Matters: If the logic of “they started it, therefore our response is beyond criticism” is accepted in one case, it must be accepted in all cases — including by adversaries whose conduct we condemn. You cannot invoke proportionality against Russia in Ukraine while dismissing it elsewhere. The principle is either universal or it is nothing.

4. Gaza: The Framework Applied

The Point: The post-October 7 war in Gaza is a textbook case of the jus ad bellum / jus in bello distinction — where a broadly accepted right to respond militarily has been used to shield conduct that multiple international courts and human rights organizations have flagged as potentially criminal.

The Evidence:

  • The October 7, 2023 Hamas attack killed approximately 1,200 Israelis and took over 250 hostages. It was the deadliest attack on Jewish people since the Holocaust. Israel’s right to respond militarily was broadly accepted under Article 51 of the UN Charter, including by the United States, EU, and virtually every Western government
  • As of early 2026, the military response has killed over 72,000 Palestinians (Gaza Ministry of Health/WHO), destroyed approximately 70% of Gaza’s housing stock, produced a declared famine (IPC classification), and displaced nearly the entire population of 2.3 million people multiple times (UNRWA, 2025-2026)
  • The ICJ issued provisional measures in January 2024 finding a plausible risk of genocide and ordered Israel to prevent genocidal acts and allow humanitarian access. The ICC issued arrest warrants for both Hamas leaders and Israeli officials for alleged war crimes. Amnesty International, Human Rights Watch, Médecins Sans Frontières, and multiple UN bodies have documented patterns of indiscriminate attacks, obstruction of humanitarian aid, and potential collective punishment (ICJ/ICC/Multiple organizations, 2024-2026)

The Logic: Acknowledging Israel’s right to respond to October 7 and acknowledging that the subsequent military campaign raises serious questions under international humanitarian law are not contradictory positions — they are the same legal framework applied consistently. The jus ad bellum question (was Israel justified in responding?) and the jus in bello question (has the response complied with the laws of war?) have different answers, and pretending they are the same question is intellectually dishonest. McNamara understood this about his own war. The question is whether we can apply the same honesty to contemporary conflicts.

Why It Matters: A 60-to-1 kill ratio, a declared famine, 70% of housing destroyed, and provisional measures from the International Court of Justice do not become acceptable because the triggering attack was horrific. If they did, then the firebombing of Tokyo was acceptable because Pearl Harbor was horrific, and the destruction of Grozny was acceptable because Chechen terrorism was horrific, and the bombing of Aleppo was acceptable because the Syrian civil war was horrific. The principle of proportionality either applies universally or it protects no one.

Counterpoints & Rebuttals

Counterpoint 1: “You can’t fight a war with one hand tied behind your back”

Objection: War is inherently brutal, and holding one side to unrealistic standards of proportionality while the other side uses human shields, hides in tunnels, and deliberately embeds among civilians is naive and unfair. The laws of war were designed for conventional conflicts between uniformed armies, not asymmetric warfare against terrorist organizations.

Response: International humanitarian law was specifically updated to address asymmetric and non-international armed conflicts — Additional Protocol II (1977) and the Rome Statute (2002) both address this. The “tied behind your back” argument assumes that IHL prohibits effective military operations; it doesn’t. It prohibits disproportionate operations — those where expected civilian harm is excessive relative to the concrete military advantage. Every military in NATO trains to these standards. The IDF itself has legal advisors embedded in operational planning for exactly this purpose. The standard isn’t perfection — it’s reasonable precaution.

Follow-up: “But Hamas uses human shields — that makes civilian casualties their fault, not Israel’s.”

Second Response: Hamas’s use of human shields is a war crime — full stop. But under IHL, the presence of combatants among civilians does not strip those civilians of their protected status. The obligation to distinguish between civilians and combatants, and to assess proportionality, remains with the attacking force. Both parties can be violating the law simultaneously: Hamas for embedding among civilians, and the attacking force for striking without adequate precaution or proportionality assessment. One side’s war crimes do not authorize the other side’s war crimes. This is not a novel principle — it’s the foundation of the Geneva Conventions.

Counterpoint 2: “Proportionality doesn’t mean equal casualties — it’s about military advantage”

Objection: People misunderstand proportionality. It doesn’t mean both sides should suffer equal losses. It means each specific attack must weigh expected civilian harm against the concrete military advantage anticipated. Israel could have legitimate military targets that justify significant civilian harm in individual operations.

Response: This is actually correct as a statement of the law — and it’s an important nuance. Proportionality under IHL is assessed attack by attack, not by overall casualty ratios. However, this technical accuracy is often deployed to avoid confronting the cumulative picture. When the pattern of attacks consistently produces massive civilian casualties, when entire neighborhoods and refugee camps are destroyed, when humanitarian infrastructure is systematically targeted, and when a famine is declared — the individual-attack framing becomes a way of missing the forest for the trees. IHL also prohibits indiscriminate attacks (those that strike military and civilian targets without distinction) and attacks where the methods or means of warfare cannot be directed at a specific military objective.

Follow-up: “So what’s the acceptable number of civilian casualties in a war against an enemy embedded in a dense urban area?”

Second Response: There is no specific number — and that’s the point. The assessment is contextual, requiring professional military judgment about feasible precautions, available intelligence, and whether the anticipated military advantage justifies the expected civilian harm. But context also means looking at the totality: when the cumulative result is over 72,000 dead, 70% of housing destroyed, declared famine, and the displacement of nearly an entire population — the claim that every individual operation met the proportionality standard strains credulity. At some point, the pattern is the evidence.

Counterpoint 3: “Applying these standards to Israel but not to Hamas is a double standard”

Objection: Hamas committed horrific atrocities on October 7 — massacres, sexual violence, hostage-taking — yet the international focus on proportionality is directed almost entirely at Israel. Where are the ICC warrants for Hamas? Where is the humanitarian concern for Israeli hostages? This selective application of IHL undermines its credibility.

Response: This objection has real merit — and must be addressed honestly. Hamas committed grave violations of international humanitarian law on October 7, including deliberate targeting of civilians, hostage-taking, and sexual violence. These are war crimes, full stop. The ICC has indeed issued warrants for Hamas leaders alongside Israeli officials, and October 7 must be condemned without qualification. But the existence of Hamas’s crimes does not exempt Israel from its own obligations — that is literally the foundational principle of IHL. The laws of war are not reciprocal: each party is independently bound. If they were reciprocal, then any army fighting an enemy that committed atrocities would have license to commit its own, and the Geneva Conventions would be meaningless.

Follow-up: “But in practice, the attention and outrage are disproportionately focused on Israel.”

Second Response: This perception is understandable but partly explained by a straightforward factor: the U.S. provides Israel with $3.8 billion annually in military aid, plus $21.7 billion in additional assistance since October 2023. Americans have standing to scrutinize how their tax dollars and weapons are used. We don’t fund Hamas. We don’t arm Hamas. We have no leverage over Hamas. The asymmetry of attention follows the asymmetry of the relationship — and in a democracy, that’s accountability, not bias. That said, advocacy for IHL should be consistent, and those who champion proportionality in Gaza should apply the same standards to Hamas, to Russia in Ukraine, to Saudi Arabia in Yemen, and to the U.S. in its own military operations.

Common Misconceptions

Misconception 1: “If a war is justified, the conduct within it is justified too.”

Reality: This conflation is exactly what the Nuremberg Principles, the Geneva Conventions, and the Rome Statute were designed to prevent. The entire post-WWII legal order rests on the separation of jus ad bellum and jus in bello. The Allied cause in WWII was just — and McNamara still said “we were behaving as war criminals.” Both things were true simultaneously. A just cause does not retroactively authorize every act committed in its name.

Misconception 2: “Proportionality means equal casualties on both sides.”

Reality: Proportionality under IHL is assessed at the level of individual attacks — whether expected civilian harm is excessive relative to the concrete military advantage anticipated. It has nothing to do with equalizing overall casualties. A war can be legally conducted with highly asymmetric casualty figures. However, when the cumulative pattern shows massive civilian harm, systematic destruction of civilian infrastructure, and declared famine, the question shifts from individual proportionality to whether the overall conduct reflects compliance with IHL’s core principles of distinction, proportionality, and precaution.

Misconception 3: “The laws of war don’t apply to fighting terrorists.”

Reality: International humanitarian law applies to all armed conflicts — international and non-international. Additional Protocol II (1977) and Common Article 3 of the Geneva Conventions specifically address conflicts involving non-state armed groups. The characterization of an enemy as “terrorist” does not create a legal black hole in which civilian protections cease to exist. The U.S. learned this painfully through Abu Ghraib, Guantánamo, and the CIA’s enhanced interrogation program — all justified under the theory that the “war on terror” existed outside normal legal frameworks.

Rhetorical Tips

Do Say

“I absolutely support the right to self-defense. What I don’t support is the idea that self-defense is a blank check. Even in WWII — the most justified war in modern history — the people who planned the firebombing of Tokyo admitted they were behaving as war criminals. If we can ask that question about our own wars, we can ask it about anyone’s.”

Don’t Say

Don’t lead with casualty numbers or accusations of genocide — this immediately polarizes and triggers defensive reactions. Start with the framework (jus ad bellum vs. jus in bello), use McNamara as a non-threatening entry point (Americans critiquing America), and then apply the principle to the current situation.

When the Conversation Goes Off the Rails

Come back to McNamara. “Here’s a man who helped plan the firebombing of 67 Japanese cities. He believed WWII was justified. And he still said: ‘We were behaving as war criminals.’ If the Secretary of Defense can say that about America’s most popular war, surely we can ask whether proportionality is being respected in any conflict — without being accused of supporting the other side.”

Know Your Audience

  • Veterans and military families: Many service members are trained in the laws of war and take them seriously. The JAG framework, rules of engagement, and military ethics training are all built on proportionality. This audience often responds to: “The troops are trained to follow these rules. Why wouldn’t we hold our allies to the same standard?”
  • Conservatives: Frame around rule of law and universal standards. “If we accept that ‘they started it’ justifies anything, then we’ve handed Russia the same argument in Ukraine. The rules either apply to everyone or they protect no one.”
  • Progressives: The humanitarian case is strongest, but ground it in the legal framework rather than emotion. The ICJ, ICC, and Geneva Conventions carry more persuasive weight than protest slogans.
  • People who say “war is hell”: Acknowledge the reality while pushing back on fatalism. “War is hell — which is exactly why humanity spent the last 80 years building rules to limit the hell. Saying ‘war is hell’ as a reason to abandon those rules is like saying ‘crime exists’ as a reason to abolish courts.”

Key Quotes & Soundbites

“If we’d lost the war, we’d all have been prosecuted as war criminals. And I think he’s right. He, and I’d say I, were behaving as war criminals. LeMay recognized that what he was doing would be thought immoral if his side had lost. But what makes it immoral if you lose and not immoral if you win?” — Robert McNamara, The Fog of War, 2003

“Proportionality should be a guideline in war. Killing 50% to 90% of the people of 67 Japanese cities and then bombing them with two nuclear bombs is not proportional, in the minds of some people, to the objectives we were trying to achieve.” — Robert McNamara, The Fog of War, 2003

“The test of a country’s commitment to human rights is whether it applies those standards to its friends, not just its adversaries.” — Senator Patrick Leahy (author of the Leahy Law)

“Self-defense is a right. Blank-check warfare is not. The difference between the two is called the Geneva Conventions.”

  • Israel-Palestine & U.S. Policy — The practical policy application of proportionality principles to the current conflict, including conditioning military aid on IHL compliance (see: Israel-Palestine & U.S. Policy)
  • The Paradox of Tolerance — Both frameworks address where to draw defensible lines: tolerance must have limits, and self-defense must have limits — for the same reason (see: The Paradox of Tolerance)
  • Both-Sides-ism & False Equivalence — The conflation of “both sides commit violence” with “both sides bear equal responsibility” is a false equivalence that proportionality analysis helps untangle (see: Both-Sides-ism & False Equivalence)
  • Military Spending & Pentagon Budget — U.S. military aid and arms transfers are the mechanism through which proportionality concerns become questions of American complicity (see: Military Spending & Pentagon Budget)

Sources & Further Reading