“That ratio is tremendously positive,” said Israeli Defense Forces (IDF) spokesman Jonathan Conricus when asked in December 2023 about Israel’s assessment that its military had killed two Palestinian civilians for every one Hamas fighter.
With these words, Conricus confirmed Israel’s point of view that killing two civilians for every enemy combatant was “proportionate,” given combat challenges. While Conricus might have been referring to the overall proportionality of self-defense under the UN Charter, other officials cited International Humanitarian Law (IHL) explicitly in the media or in military briefs, saying that if the survival of the state of Israel is at stake, higher civilian casualties are justifiable under International Humanitarian Law. Some third states seemed to agree, as well, and continue to do so: German Chancellor Scholz, for instance, still expressed “full trust” in Israel’s compliance with IHL at the beginning of the conflict, while arms exports by Germany, the UK, France and the US, “taking into account international law concerns,” reach record highs today.
In this article, I will therefore explore the ambivalent nature of the proportionality rule. It raises uncomfortable questions: Who decides what civilian casualties are “proportionate” when weighed against military gains? Does the rule actually have humanitarian value, since its text is so vague? Does the rule, therefore, not risk becoming a fig leaf for unconstrained military actions, since anyone can claim their ratios are “proportionate”? And, finally, how does one avoid the distortion of the rule and enforce it to fulfill a humanitarian purpose? To be clear from the outset: Conricus’ quote above would constitute a severe misapplication of the law, and would never pass muster before the International Criminal Court.
The proportionality rule in IHL: a double-edged sword?
What is certain is that the term “proportionality” in the concrete context of military gain versus civilian harm is rooted in IHL, which is the body of international law designed to regulate wars. One would expect, judging by the law’s name, that it can serve only humanitarian purposes. Consequently, regarding civilians, it should either minimize casualties as far and effectively as possible or prohibit them outright. One might be surprised then that the rules on targeting, specifically the proportionality rule found in Article 51(5)(b) Additional Protocol I, conditionally allow for factoring civilian deaths into the planning of a specific attack as “collateral damage.” It prohibits
b) an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive concerning the concrete and direct military advantage anticipated.
A crucial, laudable aspect is that the rule is only applied to singular, concrete attacks. It can never be applied to the conflict as a whole. The concept of weighing civilian damage against “the survival of the state” does not exist in IHL and is therefore a severe misapplication by the Israeli experts. Within attacks, the damage done must be weighed against a concrete and direct military advantage, such as the destruction of a tank or elimination of enemy combatants. Second, the rule is couched in other norms, seeking to ensure that military commanders take utmost care to spare civilian lives: The principle of distinction, which allows only military objectives to be targeted, and the principle of precaution, which obliges them to take all “feasible” measures to ensure civilian lives are spared.
On the other hand, one can criticize the proportionality rule’s built-in ambiguities for being easily exploitable, since what exactly is “excessive” is left undefined. How many civilian deaths can one attacker factor in if a mid-level commander is targeted—five, ten, or twenty? While it would be impossible to formulate a generally applicable quota, military manuals define step-by-step approaches to weigh the importance of a military goal against the collateral damage caused by a strike. Some even offer maximum ratios. For instance, immediately after Hamas attacked on October 7 2023, the Israeli military loosened its targeting rules and allowed mid-level commanders to order attacks on targets where up to 20 civilians could be at risk of getting killed.
The judgment of what is “proportionate” therefore lies completely in the eyes of the interpreter. It may be rightfully argued that the IHL wording legitimizes attacks that cost many civilian lives. A military power can state that its attack is proportionate, and as such “not excessive” under IHL, and due to the power of legal language providing authority, it might influence public opinion and political allies—as visible in Israel’s case— that killing an abundance of civilians was necessary to achieve its goal. This goal is, at least proclaimed, self-defense in most wars nowadays. If left unchecked, a series of “proportionate” attacks from the point of view of the attacker could even conceal a broader “indirect” attack on civilians, including relevance for crimes against humanity or genocide. Investigating this proportionality is the central question that has to be examined to protect civilians in war today.
History of the proportionality rule: an amalgam of humanitarian and military interests
But why is the rule’s wording so vague? This is because International Humanitarian Law carries both humanitarian and military interests. History shows how difficult it was to place real limits on warfare to begin with. Cicero already put this early on by writing “inter arma enim silent leges.” (“During war, the law is silent.”) It was also apparent in a recent speech by Pete Hegseth, who began his term as US Defense Secretary by dismissing the army’s top lawyers, and who decried rules of engagement as “stupid” in his military address. As such, there was always backlash by states to limit their ability to exercise their power to wage war. International Humanitarian Law developed slowly, starting during the 19th century, when young European nation-states viewed war as a legitimate way to conduct politics and were anxious to defend their sovereignty from threats from the outside, just as much as from the inside. The Prussian rationale of Kriegsraison was widely accepted, which promulgated that whatever is necessary to achieve victory is allowed and needs to be done, including bombing civilians, who were regarded as enemies on par with enemy soldiers.
In response, the proportionality rule only arose slowly in conjunction with the principle of distinction, in response to the carpet bombings of the two world wars. Yet, in their aftermath, major military air powers, such as the UK and the US, were reluctant to put an effective restraint on their technological advantage from the air, as they anticipated conflicts with less technologically advanced adversaries. Only through hard-fought negotiations by the International Committee of the Red Cross and civil society, as well as pressure from public opinion after serious war crimes in the Vietnam war did the golden moment appear for codification of the targeting principles in the 1977 Additional Protocols.
Born out of compromise, IHL has ingrained the premise of practicability, which means it still allows certain belligerent acts that are necessary to achieve the end goal of military victory. The “necessary evil”—even rooted in IHL’s Necessity Principle—therefore includes killing innocent civilians who happen to be in harm’s way, and factoring this into the planning stage of an attack. The proportionality rule becomes somewhat the convergence point of humanitarian and military interests. Excessiveness being undefined is a result of diplomatic ambiguity. As a testimony of time, IHL proportionality reconciles these two interests. It is, owing to its open wording, neither purely humanitarian nor purely permissive. Its judgment lies in the eyes of the viewer. It thus highlights a truth of IHL as a branch of Public International Law: It can only unfold its humanitarian value either way, like many rules in law, through a balanced interpretation that stays true to its purpose. And this purpose, as stated by eminent scholar Hersch Lauterpacht:
“We shall utterly fail to understand the true character of the law of war unless we realize that its purpose is almost entirely humanitarian in the literal sense of the word, namely, to prevent or mitigate suffering and, in some cases, to rescue life from the savagery of battle and passion. This, and not the regulation and direction of hostilities, is its essential purpose.”
The importance of rigorous enforcement
When monitoring Israel’s war in Gaza, many wonder whether certain attacks were proportionate, but no one except the International Criminal Court can give a final answer since the rule is formulated so openly. The core issue persists: Does the rule actually impose tangible limits? Most deaths occurred as the Israeli military and government kept on justifying their attacks by saying that they were directed at a military objective, such as Hamas fighters, and any, even very high, damage to civilians was merely incidental, yet proportionate.
In fact, the political conduct of Israel in the conflict confirms that the proportionality rule has limits and cannot be overstretched endlessly. In March 2025, Israel’s military conducted an attack which stretched all principles of IHL in a way that it is almost impossible to justify them argumentatively. The operation “Might and Sword”, directed at killing four senior Hamas officials, took the lives of 483 civilians, including 183 children. It prompted even Israeli experts to refute that this was proportional in hindsight. Israeli military experts knew this and first tried to publicly distort the rule by wrongly applying it to the conflict as a whole, as mentioned above. They basically framed the concrete military advantage to be factored in as “winning the war”, which is reminiscent of the Kriegsraison reasoning, the very doctrine IHL seeks to contain. This need for its misapplication confirms its limits, and least an anticipated discomfort when there is a need to justify oneself.
A second clue that Israel does not want to be pinned down on proportionality was its silence on the issue after March 2025. This silence gave third states little occasion to step in and criticize the disproportionate nature of some attacks. It was more feasible, even if done tentatively, to condemn more obvious violations, such as bombings of hospitals or journalists and withholding humanitarian aid, as these violations are easier to pin down. This also still shows that the rule’s vagueness has a flip side: It makes third states reluctant to call it out, and it can even be abused if it is not strictly and correctly applied. Truly, the rule only unfolds its value through the Public International Law main enforcer: Shame, induced by third states, humanitarian actors, the media and public opinion. Violators need to feel uncomfortable at least, if not threatened to face legal actions through the ICC arrest warrants. And during the Gaza war, even though NGOs have been vocal about proportionality, third states have largely remained silent about it. This makes the proportionality rule largely void and toothless, because few speak about its concrete limits with its humanitarian purpose in mind.
Conclusion: The limits of IHL’s civilian protection
Overall, the humanitarian value of the proportionality rule, in the right hands, is to back up the authority to criticize disproportionate attacks from the perspective of the person applying it. It does not offer a definite ratio—to prescribe this would be impossible—nor does it completely prohibit attacking civilians. From a military point of view, this leaves plenty of justificatory room to exploit the legacy which military powers left at the negotiation table. IHL targeting rules are not as purely humanitarian as their name would suggest. Their open wording can only develop its limiting effect within the limits of Public International Law enforcement. In the Gaza war, its consistent distortion by Israel shows that, if it were discussed in its correct form, the rule does have an effect of restraint, not a legitimizing one. But rulebreakers can get away if there is silence, and so we need rigorous enforcement and political commitment for it to function.
From a humanitarian point of view, this is lamentable. Killing innocent civilians, after all one of the greatest interferences with a persons human rights imaginable, should be clearly prohibited or punished, but the doctrine of IHL is constructed in a way that does not provide for this. Due to its drafting history, it is characterized by the DNA of state survival—not human survival. For those who believe that state survival cannot justify killing civilians, IHL may simply not be the only legal instrument to apply. In the wider International Law discourse, it is now increasingly contended that IHL cannot just override the core right to life under International Human Rights Law in all situations, which remains applicable during armed conflict. Therefore, international lawyers and scholars increasingly turn to Human Rights Law with its more individual-centered protection, to interpret the proportionality rule and the responsibility for the killing of civilians in armed conflict.
