King of Armenia (1226-1269) and leading promoter of Christian alliance with the Mongols.
The rival Armenian dynasties of the Het‘umids and Rupenids were reconciled under King Leon I (1219), and the marriage of Het‘um to Leon’s heiress, Isabel, ended the feud in 1226.
Het‘um initially acknowledged the overlordship of the Saljûq sultanate of Rûm but used the arrival of the Mongols to exchange suzerains: after the battle of Kose Dagh (1243), he ingratiated himself with the Mongols by handing over the Saljûq sultan’s family. His brother, Smpad, and then Het‘um himself traveled to the Mongol capital, Qaraqorum, to obtain recognition from the Great Khan (1253-1256).
Following the Mongol invasion of Syria under Hülegü in 1260, the Armenian kingdom expanded eastward to the Euphrates, and Het‘um had a notable role in the Mongol occupation of Aleppo and Damascus, gaining the enmity of the Mamlûks.
Het‘um continued to fight for the Mongols, but by 1266 the Mamlûks had turned to the offensive. Despite Het‘um’s attempts to negotiate a truce, a Mamlûk force attacked Cilicia, defeating the royal army trying to hold the Amanus Gates and going on to ravage most of the Cilician plain; in the fighting, Het‘um’s son Leon was captured and another son killed. In 1268 Het‘um surrendered to the Mamlûks a series of castles on his eastern borders and obtained the release of his son. Having consulted the Ilkhan Abagha, Het‘um abdicated in favor of Leon in 1269, dying a year later.