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.