New Delhi, Oct. 26 -- FOR FOUR years an uncomfortable truce in Yemen's long civil war has prevailed. But now open conflict is breaking out again. The Houthis, Iran-backed rebels, have accused Yemen's internationally recognised government and Saudi Arabia, its most important ally, of planning a big offensive. On July 30th their leader, Abdul-Malik al-Houthi, said his forces would "respond to their full-scale escalation with one of our own". Throughout August they have launched drone and missile attacks against government positions, killing dozens of soldiers and civilians. Yemen's regular army has struck back hard.

The Houthis think they have much to gain from restarting the war. Since mid-July their militia has been firing at Saudi-linke...