Even as Israel has paused its offensive in the Gaza strip, the most difficult phase of its campaign is yet to come. The Israel Defense Forces (IDF) have spent weeks using artillery and airpower to bomb Hamas terrorist fighters and facilities, followed by tanks and ground troops. But, as the IDF announced in its warning to civilians to leave the northern Gaza strip, “Hamas terrorists are hiding in Gaza City inside tunnels underneath houses and inside buildings populated with innocent Gazan civilians.” Once Israel decides to resume its offensive, it will have to face the difficult operational and tactical challenges of urban warfare in a political environment where critics and even some allies are demanding a cease-fire to protect civilians.

Before turning to the legal and policy issues surrounding urban combat in Gaza, we should make clear that Israel has the right to use force. While scholars and governments may argue over whether the Gaza strip amounts to an independent territory (unoccupied by Israel) and Hamas constitutes the legitimate government there, Hamas undeniably launched an attack on Israel on October 7, 2023. Hamas’s systematic murder of unprotected civilians violated the core principle of the laws of war, which prohibit intentional attacks on non-combatants. Israel has the legal and moral right to act in its self-defense to stop Hamas’ campaign and to prevent future assaults.

Israel’s right to use military force in Gaza (ius ad bellum), however, does not relieve it of the obligation to obey the laws of war as it executes its operations (ius in bello). Israel has an obligation to target only military personnel and assets, and the productive capacity that supports them (the principle of distinction), and to use force—especially that which harms civilians incidentally—only in proportion to the gains presented by the military objective (the principle of proportionality). It is one of the great achievements of Western civilization that, over the millennia, nations at war have sought to limit hostilities to protect innocent life. Whereas Thucydides reports in his history of the Peloponnesian War that victorious city-states would execute the men and sell women and children into slavery after sieges, the Twenty-First Century’s Western professional armed forces seek to avoid striking civilian buildings, such as churches, hospitals, and apartment buildings; and deliberately shooting innocents.

This is not to say that legitimate military operations can only fight other militaries in a sanitized environment—a strike on a military target may incidentally harm civilians nearby—or that even armies today do not deliberately violate the rules (such as Russia in Ukraine, ISIS and the resistance in Iraq and Syria in its civil war), but only to recognize that western militaries have given much more weight to considerations of humanity in battlefield operations.

Urban warfare places these principles under stress. Distinction becomes more difficult due to the close quarters between combatants and civilians, risking both people and buildings. Proportionality proves more challenging as striking military targets in dense population areas increases collateral harm to civilians. Israel has sought to reduce these costs on civilians by issuing a warning to Palestinians to leave Gaza City and the northern half of Gaza before it began ground operations. Despite the condemnation by the International Committee of the Red Cross, United Nations officials, and foreign governments, Israel’s warning prompted a caravan of civilians to flee to south Gaza, which somewhat reduced the proportion of the civilian population exposed to IDF strikes.

But now these same authorities, as well as an American anti-war left, are demanding a cease-fire because urban warfare in Gaza City will involve too many civilian casualties. Israel, however, is not bound by the idea that there is a fixed ratio of harm between military targets and incidental civilian deaths beyond which Israel may not go, or that international law requires Israel to refrain from operations in a city.

Those who claim Israel has “clearly” violated international law seem to assume the law of armed conflict (LOAC) is as clear as the U.S. tax code. The main treaty setting out permissible tactics in armed conflict, Additional Protocol I (1977) (AP I) to the (1949) Geneva Conventions, was negotiated in the wake of the Vietnam conflict. It is full of general phrases, papering over differences between Western and Third World delegates to the drafting conference. It has never been ratified by Israel, nor by the United States and a number of other countries.

Israeli and American military lawyers acknowledge that their armed forces should conform with the main tenets of AP I, as a statement of customary law. But they are not obligated to conform to interpretations made by the International Red Cross or other advocacy groups, since these bystanders have no actual experience in combat operations, and “custom” under international law is determined by the relevant practice of actual states. While the U.S. tax code can be clarified by the IRS and innumerable federal court rulings, there is no accepted administrative authority on the law of armed conflict, and scarcely any authoritative court rulings on AP I. Many AP I provisions were incorporated into the Statute of the International Criminal Court (1998) but neither Israel nor the United States has ratified that treaty.

In no international conflict since the completion of AP I did both sides adhere to all of its strictures, especially in the strict understanding advanced by the Red Cross. In many conflicts, neither side did. And it is a recognized principle of treaty interpretation that subsequent practice is a relevant indication of what parties to a treaty understand it to mean. Actual state “practice” is even more significant to interpreting customary law—the unwritten norms which still govern much of the laws of war (the United States, for example, takes the position that many parts of AP I merely express customary law, and so will follow its terms, even as it remains a non-signatory). Given how much more experience the U.S. military has in actual combat operations over the past three decades than have other Western states, the only ones with any serious scruples about LOAC, it should count for a great deal that U.S. military specialists in the law of armed conflict have not found fault with Israel’s tactics.

Critics claim that Israel has committed a “war crime” by suspending previous deliveries of water, food, fuel, and electric power to Gaza. Siege warfare has always been an accepted tactic in war. The Union army cut off food supplies to Vicksburg in 1863, just as the Prussian Army did to Paris in 1871. The Nuremburg tribunal acquitted the commander of the German U-boat force for trying to cut off Britain from food supplies. It held that the practice could not be contrary to international law because the Allies had imposed their own food blockades in both world wars. For the same reason, a German general was acquitted in a subsequent war crimes trial for imposing a food blockade of Leningrad and shooting at civilians trying to escape it.

What the text of AP I actually says is that within the battle space, an attacking force should not attack sources of food and water on which civilians depend. What it does not say is that an attacker must provide food, water, and fuel to civilians while conducting military operations. The historic justification for denying all provisions to a besieged enemy was that there was no way to assure supplies would be delivered to civilians rather than diverted to the military. Hamas has been relentless about supplying its own forces from past humanitarian aid: for example, pipes intended to expand water delivery were used to make rockets, and cement for civilian housing was diverted to tunnel construction.

The same considerations apply to charges that Israeli targeting of bombing attacks in Gaza have been “indiscriminate” and “disproportionate.” AP I prohibits deliberate attacks on civilians and “civilian objects” such as schools and hospitals. But it does not make such sites immune from attack if known to be used for military purposes. Hamas is notorious for hiding its weapons and fighters amid civilian facilities. AP I does have a provision against attacks which cause incidental (that is, unintended) injury to civilians and civilian infrastructure that is “excessive in relation to the concrete and direct military advantage anticipated.”

But there are so many uncertainties packed into this test that no international tribunal (neither the ICC nor its predecessor, criminal tribunal for the former Yugoslavia, has ever attempted a prosecution for violating this limitation. It is particularly hard to apply here, when casualty reports are based on notoriously unreliable claims by Hamas-controlled public health authorities in Gaza. No outsiders can judge all the considerations which Israeli commanders had in view when authorizing attacks on particular targets in the heat of the conflict.

Applying the rules of war developed for combat between Western militaries becomes even more problematic given the nature of Hamas. Hamas is a terrorist organization that refuses to obey the rules of war, as it did by attacking a large music festival and undefended villages on Oct. 7. Its fighters neither wear visible uniforms nor operate in open, clear military formations, but instead seek to blend into the general population, as Hamas hides its personnel and assets among civilians.

Indeed, Hamas succeeds precisely by violating the laws of war and blurring the line between combatants and non-combatants, both on its own part and that of its victims. Extending unwarranted legal protections to Hamas only multiplies its incentive to continue disregarding the principles of humanity on the battlefield.

But Hamas’ activities are even more pernicious. Not only does it target the innocent and use civilians as shields to limit its own losses, but it deliberately invites attacks on its own population as a means of political and legal warfare. Widely transmitted images of civilian deaths generate sympathy for Hamas within the Arab world, and raise the political pressure on Israel from the United States, which provides Israel crucial military supplies, intelligence support, and financial backing. Hamas’s strategy became clear when it sought to prevent Gazans from complying with the Israeli warnings to evacuate the northern strip. For Hamas, the more Gazan civilians killed by Israeli strikes, the better. The laws of war do not easily apply to an enemy that seeks victory by deliberately increasing its own civilian casualties.

The ultimate issue is not a technical question of treaty law or customary law. If the law of armed conflict makes it impossible for a modern Western army to defeat terrorist warlords hiding behind civilians, that version of LOAC is a threat to civilization itself.

overlay image