What limits do the laws of war impose on combatants?

ON OCTOBER 24th António Guterres (pictured), secretary-general of the UN, called for an end to the “epic suffering” caused by Israel’s blockade and bombing of the Gaza strip. Hundreds of people had died in the preceding 24 hours, and on Tuesday only eight aid lorries had entered the territory. Such conditions, Mr Guterres said, amounted to “collective punishment of the Palestinian people” for the bloody attack on Israel carried out on October 7th by Hamas, the militant group that runs Gaza. He claimed there had been “clear violations” of international law in recent days: by Hamas, which is using civilians as human shields and holding more than 200 hostages; and by Israel, when it ordered the evacuation of northern Gaza but continued to bomb the south. Israel condemned Mr Guterres’s comments and said he should resign. But he is not alone in calling for a measured response. On October 22nd, a joint statement from the leaders of six countries, including America, urged Israel to adhere to “international humanitarian law” (without accusing the country of having broken it). What limits does the law of armed conflict impose on belligerents?

The principles that underlie the rules of warmaking go back centuries, often to religious texts. Deuteronomy 20:10, for example, instructs warriors to “offer peace to the people” before attacking. In 1625 Hugo Grotius, a Dutch philosopher, gave such rules a secular foundation. In “On the Law of War and Peace” he lamented a “lack of restraint in relation to war” and posited a “common law among nations” that would impose limits. Three centuries later world leaders settled on such a law in the guise of the Geneva Conventions of 1949. All of the world’s countries have signed on to these principles, which protect wounded and sick combatants, prisoners of war, and civilians during wartime. (Some countries have agreed with reservations, including the rejection of international courts’ jurisdiction over their actions.) The law of war also encompasses customary rules—general practices accepted as law despite not being formally agreed upon—and more recent treaties prohibiting the use of biological and chemical weapons, among other grisly munitions.

Violations of the law of war are difficult to prosecute; many go unpunished. But armies that strive to adhere to the law of armed conflict follow four basic principles. The most sweeping, humanity, has its origins in the so-called Martens clause—a provision in the Hague Convention of 1899, a precursor to the Geneva Conventions, that gives individuals protection under the “dictates of public conscience” in situations when no specific treaty governs. The second is military necessity, which permits only the degree of conflict that is required to achieve a valid military objective, such as the submission of the enemy and not, say, destruction of the natural environment or historic sites. The third, distinction, requires armed forces to clearly “distinguish themselves from the civilian population while they are engaged in an attack” so as to prevent the inadvertent targeting of non-combatants. And finally, proportionality mandates that the pursuit of valid military goals cannot cause undue civilian suffering. If the collateral damage to civilians’ lives or homes is “excessive” when set against the “direct military advantage anticipated”, proportionality requires combatants to limit—or hold—their fire.

Humanity is a worthy starting point for the law of war but, because the principle is hazy, it can be hard to tell when combatants fail to uphold it. Other standards can be applied more clearly. Pursuing armed conflict to wipe out a population or despoil their land is plainly out of bounds. Soldiers who fail to wear proper uniforms violate the principle of distinction: Hamas fighters, some of whom allegedly wore Israeli military uniforms during their attack on the country, broke this rule. Military assaults that take no account of civilian casualties or deliberately target them also break international law. But proportionality, the principle guiding the latter example, is often misunderstood. It does not hinge on absolute casualty counts but on how harm to civilian lives and infrastructure is weighed against expected military gains. That means, theoretically, that rather a lot of suffering could be permissible. In 2013 Amnesty International and Human Rights Watch claimed that American drone strikes in countries including Afghanistan, Iraq and Pakistan, in which many civilians died, may have been disproportionate—a claim that Barack Obama, then America’s president, denied, saying that in each case the potential loss of civilian life had been carefully weighed.

There is no question that Hamas’s attacks on Israelis violated the law of war, and Mr Guterres is right that in using civilians as unwilling human shields it is committing a further breach of the Geneva Conventions. Israel, for its part, is allowed to instruct Palestinians to move away from the northern half of Gaza for their own protection, but this displacement must be temporary and adequate humanitarian relief must be provided. And under any interpretation of the law of war, Israel’s proportionality calculus must take account of the many civilian casualties its air strikes and pending ground invasion will cause. But legal opinion is split on how to undertake this accounting. Israel has in the past interpreted the rules to exclude damage to apartment buildings if terrorists occupy them. And although the International Committee of the Red Cross contends that human shields must be protected unless they are physically blocking a military objective, Israel and America believe that civilians who voluntarily serve as human shields are participants, not bystanders. Telling the difference is hard at the best of times—and the fog of war makes clarity harder still. ■