On this date in 1284, the deposed Mongol ruler Tekuder was put to death. The Mongols had conquered half the world on the back of steppe horses and religious toleration. Mongols variously adopted Nestorian Christianity, Buddhism, and Islam, as well as tribal shamanism; it even sponsored debates among the rival confessions. What counted in the end for the men who commanded its armies was wins and losses. Our man Tekuder was the son of Hulagu Khan, a grandson of Genghis Khan who exemplified pluralistic competence. The son of a Christian but an eventual convert to Buddhism, Hulagu Khan’s signal achievement...