Gaza, Ukraine, and the breakdown of international law

by Oona Hathaway

Hamas’s attack on Israel and Israel’s response to it have been a disaster for civilians. In its October 7 massacre, Hamas sought out unarmed Israeli civilians, including women, children, and the elderly, killing close to 1,200 people and taking around 240 hostages. Israel’s subsequent air and ground campaign in Gaza has, as of June 2025, killed more than 55,000 people. More than 50,000 children have been killed or injured. The Israeli offensive has also displaced close to two million people (more than 90 percent of the population of Gaza), left the majority of the population at risk of starvation, and damaged or destroyed 92 percent of all residential buildings in Gaza. There is no functional hospital left in northern Gaza. Hamas, Israel maintains, uses civilian structures as shields, operating in them or in tunnels beneath them—perhaps precisely because such buildings have been considered off-limits for military operations under international law.

International humanitarian law, also known as the law of war or the law of armed conflict, is supposed to spare civilians from the worst calamities of conflict. The aim of this body of law has always been clear: civilians not involved in the fighting deserve to be protected from harm and to enjoy unimpeded access to humanitarian aid. But in the Israel–Hamas war, the law has failed. Hamas continues to hold hostages and has used schools, hospitals, and other civilian buildings to shield its infrastructure, while Israel has waged an all-out war in densely populated areas and slowed the flow of desperately needed aid to a trickle. The result has been utter devastation for civilians in Gaza.

The conflict in Gaza is an extreme example of the breakdown of the law of war, but it is not an isolated one. It is the latest in a long series of wars in the years since 9/11, from the US-led “war on terror” to the Syrian civil war to Russia’s war in Ukraine, that have chipped away at protections for civilians. From this grim record, it might be tempting to conclude that the humanitarian protections that governments worked so hard to enshrine in law after World War II hold little meaning today. Yet even a hobbled system of international humanitarian law has made conflict more humane. Indeed, for all the frequent transgressions, the existence of these legal protections has provided continuous pressure on belligerents to limit civilian casualties, provide safe zones for noncombatants, and allow for humanitarian access— knowing they will face international consequences when they do not.

After the horrors of World War II, the United States and its allies established the Geneva Conventions, the four treaties of 1949 that lay out elaborate rules governing the conduct of war. The laws of war are once again being severely tested. It is time for the states that are committed to the law to take action to renew and strengthen it—or we risk a return to the unrestrained wars of the past.

License to Kill

The law of war offers a tradeoff. Soldiers of a sovereign nation can be lawfully killed in armed conflict. In exchange, they are granted immunity that allows them to commit acts that in any other context would likely be considered crimes—not only to kill but also to trespass, break and enter, steal, assault, maim, kidnap, destroy property, and commit arson. This immunity applies whether their cause is just or unjust.

There are limits—which, for most of history, were modest. Hugo Grotius, the early-seventeenth-century Dutch diplomat who has been called “the father of international law,” wrote that soldiers should be prohibited from using poison, killing by deception (for example, after feigning surrender), and rape. In Grotius’s framework, these three offenses made up the only exceptions to a soldier’s license to kill. Enslavement, torture, pillaging, and the execution of prisoners were all allowed; so was the intentional killing of unarmed civilians, including women and children. Although few treaties governed the conduct of war at the time, countries in western Europe widely accepted these rules as customary international law.

According to Grotius, soldiers were not allowed to massacre civilians whenever they liked. They were legally permitted to take the steps necessary to enforce the rights on which the enemy had infringed—and nothing more. If killing women and children did not advance the war effort, there was no justification for doing so. Yet even if the senseless slaughter of innocent civilians was technically illegal under international law at the time, those who committed it could not be held accountable; such deeds, Grotius observed, could be “made with impunity.” The lack of legal remedy for attacks on civilians began to be addressed only in the middle of the eighteenth century, when countries gradually adopted the principle of distinction, which requires soldiers to distinguish between combatants and civilians. The rules governing war continued to evolve over the course of the nineteenth century. But the new constraints, important as they were, did little to insulate civilians from attacks.

The conflict in Gaza is an extreme example of the breakdown of the law of war, but it is not an isolated one. It is the latest in a long series of wars in the years since 9/11.

The Postwar Reckoning

During World War II, more than 30 million civilians were killed. In the aftermath of such catastrophic violence, it was clear that new and stronger rules were needed to regulate war. In 1949, a series of international conferences convened by the International Committee of the Red Cross established the four Geneva Conventions in an effort to prevent the most brutal violence of war. Although Grotius offered just three prohibitions to guide states in war, the Geneva Conventions and, later, its three Additional Protocols filled hundreds of pages with specific rules for almost any scenario.

Unlike the early laws of war, the Geneva Conventions and their Additional Protocols prohibited not just senseless violence but also some forms of violence that advanced war aims. To adhere to the conventions, parties to a conflict must distinguish between civilians and combatants and between civilian places and military ones. Above all, they may never intentionally target civilians or “civilian objects,” such as schools, private homes, construction equipment, businesses, places of worship, and hospitals that do not directly contribute to military action. And civilians must never be the target of reprisals. The principle of proportionality, codified in 1977 in Additional Protocol I, acknowledges that sometimes armies will harm civilians and civilian objects when pursuing military objectives. But the rule requires that the damage not be “excessive in relation to the concrete and direct military advantage anticipated.” The principle of precaution, moreover, requires that armies must take constant care to spare civilians and civilian objects, even if doing so might slow down military operations.

The Geneva Conventions, their protocols, and the customary international law that has grown around them take an important step beyond the rules that came before. They aim to protect civilians from harm even when that harm might serve a strategic purpose. Thus, an attack on a military target that would help a belligerent’s war effort is prohibited if it would hurt too many civilians.

In many ways, the Geneva Conventions have been remarkably successful. All four conventions have been ratified by all UN member states. Most countries have adopted military manuals that translate the conventions into concrete rules meant to guide the conduct of their armies. Many have enforced these rules against their own soldiers. Yet these elaborate and ambitious rules were shaped by wars that were very different from most conflicts today.

Since the end of World War II, wars between states have sharply declined, but conflicts involving nonstate armed groups have risen. The Geneva Conventions say little about the latter. Only one article, Common Article 3, specifically applies to wars with nonstate groups. Protecting civilians in war, it turns out, is much harder when one of the belligerents is a nonstate actor. Combatants belonging to nonstate groups generally don’t wear uniforms. Although their members may assemble, train in camps, and be organized under a hierarchical leadership, they tend to operate in places where civilians are also present. As a result, it can be extremely difficult to tell them apart from ordinary civilians.

Self-Defense Classes

The 9/11 attacks and the US response to them inaugurated a new era of war that has pushed international humanitarian law to a breaking point. Before 2001, legitimate self-defense under international law was generally understood to apply only when one country was defending against an attack from another. Until then, few countries had cited nonstate actors as their primary reason for using force in self-defense.

After 9/11, self-defense claims changed. The United States justified its invasion of Afghanistan by arguing that it was responding to, as the Bush administration informed the UN Security Council, the “ongoing threat to the United States and its nationals posed by the Al-Qaeda organization.” Within a year, Australia, Canada, France, Germany, New Zealand, Poland, and the United Kingdom had also filed claims of self-defense against al-Qaeda. And it was not long before countries began making claims against other nonstate groups. In 2002, for example, Rwanda cited a right of self-defense against the Interahamwe, a militia group. And in 2003, Côte d’Ivoire cited the same right against “rebel forces.”

To confront groups such as al-Qaeda and the Islamic State (also known as ISIS), the United States and its allies came to rely on what they dubbed the “unwilling or unable doctrine”—the theory that action against a nonstate threat is justified as long as the country in which the nonstate actor is found is unwilling or unable to suppress the threat. In most cases, the United States sought the consent of governments to target nonstate actors in their territories. Iraq, Somalia, Yemen, and, while the Taliban was out of power, Afghanistan all agreed to US intervention. When states would not consent—for example, Syria—the United States used the unable or unwilling theory, explicitly endorsed by fewer than a dozen countries, to justify using military force.

Since the end of World War II, wars between states have sharply declined, but conflicts involving nonstate armed groups have risen. The Geneva Conventions say little about the latter.

As Washington went to war with nonstate actors, it struggled with how to distinguish the civilians it was allowed to kill according to the Geneva Conventions—those “who take a direct part in hostilities”—from those it was not. If a civilian who was not a member of ISIS performed a task for the group—say, placing an improvised explosive device on a road—and then returned to work as an ordinary laborer, could that person still be targeted?

In 2009, the International Committee of the Red Cross issued guidance to governments on how to protect civilians when fighting nonstate actors. The ICRC document reiterated the rule that civilians must be protected against direct attack “unless and for such time as they take direct part in hostilities.” Many countries rejected the ICRC’s guidance, including the United States and the United Kingdom, which came up with their own interpretation of the Geneva Conventions that were far more permissive.

Blurred Lines?

To address the changing reality of urban combat, the United States and other countries adopted new policies that once more put civilians in the crosshairs. At the center of this shift was the concept of so-called dual-use objects. According to international humanitarian law, all sites are either military or civilian; there is nothing in between.

The clear-cut division between civilian and military often fails to match the reality on the ground. There are many sites and structures that serve important civilian purposes but, by virtue of having some military use, may be considered military objectives—for example, trains, bridges, power stations, and communications infrastructure. Even an apartment building, if part of it serves for weapons storage, can be considered dual-use. More controversially, the United States considers sectors of the adversary’s economy that may help sustain a war as legitimate targets.

The Department of Defense Law of War Manual maintains that a given industry’s or sector’s “effective contribution to the war-fighting or war-sustaining capability of an opposing force is sufficient.” This means that banks, businesses, and indeed any source of economic activity that contributes to an adversary’s ability to sustain itself could be fair game. And because members of nonstate groups often rely on the same sources as ordinary civilians for food, fuel, and money, these areas of the economy that are essential to civilian life are regularly in the direct line of fire.

The military logic behind Israel’s air and ground campaign in Gaza is, in part, a result of these incremental changes, to which both the United States and Israel have contributed for decades. In Gaza, there are few objects or structures that Israel does not consider dual-use. Meanwhile, Israel maintains that Hamas knows the law of war and has sought to protect its military infrastructure by hiding its activities in tunnels under civilian structures, such as hospitals, that the law protects from attack—in the process rendering them lawful targets.

This has meant devastation for civilians in Gaza. Hospitals and schools where those displaced by the war sought refuge have been targeted in large-scale attacks, killing thousands. The problem has been compounded by Israel’s expansive interpretation of proportionality. As Eylon Levy, an Israeli government spokesperson, told the BBC, proportionality in Israel’s view means that the collateral damage of a given strike must be proportionate to the expected military advantage. “And the expected  military advantage here,” he explained, “is to destroy the terror organization that perpetrated the deadliest massacre of Jews since the Holocaust.”

Israel has turned a principle that was meant to shield civilians into a tool to justify violence. Its approach to assessing proportionality—not strike by strike but in light of the entire war aim—is not how militaries are supposed to carry out their assessments. Rather, the principle of proportionality prohibits a given attack where the expected harm to civilian people and places is “excessive” compared with the “direct military advantage” that the attack is supposed to achieve. By weighing any single instance of harm to civilians against a perceived existential threat, Israel can justify virtually any strike as meeting the requirements of proportionality; the purported benefits always outweigh any costs. Unsurprisingly, this approach has led to a war with few restraints.

Caught in the Crossfire

Civilians have also suffered in other recent conflicts. During the Syrian civil war, the Syrian government repeatedly gassed its own people, wiping out entire neighborhoods in an effort to suppress the opposition. In 2018, a UN report found that Syrian forces, supported by the Russian military, had attacked hospitals, schools, and markets. In 2015, Saudi Arabia led a coalition of states in a campaign to defeat the Houthi rebels, who had launched cross-border attacks against it and seized the Yemeni capital, Sanaa. A team of UN investigators found that coalition airstrikes—which the United States supported with midair refueling, intelligence, and arms sales—had hit residential areas, markets, funerals, weddings, detention facilities, civilian boats, and medical facilities, killing more than 6,000 civilians and wounding over 10,000. The strikes on essential infrastructure, including water treatment plants, created a cholera epidemic that killed thousands, most of them children.

Ukraine has also been the site of barbaric attacks against civilians. Russian forces carried out summary executions, disappearances, and torture in Bucha and beyond. They indiscriminately bombed Mariupol, damaging 77 percent of the city’s medical facilities in the process. Throughout the war, Russia’s attacks on Ukraine’s energy grid have left millions of civilians without electricity, water, or heat.

Technological innovations threaten to further erode the line between civilians and combatants. In Ukraine, for example, the same app that Ukrainians use to file taxes can also be used to track Russian troops.

Meanwhile, technological innovations threaten to further erode the line between civilians and combatants. In Ukraine, for example, the same app that Ukrainians use to file taxes can also be used to track Russian troops. Using an “e-Enemy” feature, Ukrainians can submit reports, photos, and videos of Russian troop movements. Yet this makes those same civilians vulnerable to attack, since any civilian who uses the app to alert Ukrainian forces of Russian military activity might be regarded as “directly participating in hostilities” and therefore considered a legitimate target. Ukrainian data servers store both military and civilian information, likely rendering computer networks and the information stored in them dual-use objects. Ukraine created an “IT army” of more than 400,000 volunteers who work with Ukraine’s Defense Ministry to launch cyberattacks on Russian infrastructure. These Ukrainians may not realize that by volunteering their services, they have, according to international law, become combatants in an armed conflict.

Cause for Constraint

One pessimistic takeaway from the wars in Gaza and Ukraine may be that the hard-won lessons of World War II have been forgotten and efforts to use law to protect civilians from war are pointless. But as brutal as the current conflicts are, they would likely be even more horrific without these rules. A careful reading of the current era would show that rather than altogether abandoning the protections of civilians enshrined in the Geneva Conventions, belligerents in recent wars have been making those protections less effective by severely restricting what counts as civilian. And the United States has played a key part in this shift.

Since 9/11, Washington has used its power to weaken constraints on the use of force, aggressively interpret the right to self-defense, and allow for more expansive targeting of dual-use sites and structures. These positions have created greater flexibility for the US military, but they have also placed more civilians in harm’s way. Following the United States’ lead, other countries, including France, Israel, Saudi Arabia, Turkey, and the United Kingdom, have likewise loosened constraints on their own militaries.

To its credit, the Biden administration took some steps to reverse this trend and strengthen the law of armed conflict. In 2022, the Defense Department announced a detailed plan for how the US military would better protect civilians (known as the “Civilian Harm Mitigation and Response Action Plan,” or CHMR-AP), and in February 2024, the Biden administration said that it would require foreign governments to promise that any US weapons they received would not be used to violate international law.

Unfortunately, since President Donald Trump took office in January 2025, this modest progress has been halted and even reversed. It appears that any constraints the US government had placed on the Israeli government’s use of US-provided weapons have been lifted. Meanwhile, the Trump Administration has launched an attack on the International Criminal Court, levying crippling sanctions on lawyers and judges at the Court and undermining its accountability efforts in the process.

This means that any improvements that will be made, at least in the near term, are going to have to happen without the United States. This may be daunting, but it is far from impossible. Indeed, if anything good is to come of the Trump Administration’s disdain for international law, it is that states that are committed to its principles have little choice but to recognize that they have to take responsibility for its success. No single state acting alone can have the impact of the United States, but states acting together could lead to significant change.

Photo: Zyanya Citlalli. Unsplash+

This article appears in the 2025-26 Berlin Journal (39). An earlier version of this article was first published in the May/June 2024 issue of Foreign Affairs.