Battle of Qatwan

After his defeat at Khujand in 1137 the Western Karakhanid khan Mahmud II turned for protection to his overlord, the Seljuk sultan Ahmad Sanjar, who ruled from Merv. The Karluk tribes of Transoxiana, at odds with both, sought the protection of the gurkhan, and in 1141 Sanjar led a great army across the Amu Darya.

On 9 September 1141 (5 Safar 536) the armies met on the Qatwan steppe north of Samarkand. The Qara Khitai horsemen — reinforced, according to some sources, by Karluk warriors — surrounded the Seljuks and drove their centre into the valley of the Dargham, about 12 km from Samarkand, where many perished; medieval writers give figures for the dead ranging from about eleven thousand to a hundred thousand. Sanjar escaped with a handful of men to Termez, while his wife and many of his commanders were captured. Yelü Dashi spent ninety days in Samarkand, accepting the submission of its Muslim notables, and made Mahmud’s brother Ibrahim khan there; in 1142 his troops ravaged Khwarazm, and its ruler Atsiz agreed to pay tribute.

The battle ended Seljuk power north of the Amu Darya and made the Qara Khitai the paramount power of Central Asia for decades. Garbled news of it reached the Crusader East: in 1145 Hugh, bishop of Jabala in Syria, told Pope Eugene III at Viterbo — as the chronicler Otto of Freising recorded — of a Nestorian priest-king John in the Far East who had defeated the brother kings of the Medes and Persians, taken Ecbatana and set out to help Jerusalem, but could not cross the Tigris. Historians such as Robert Silverberg connect this first report of Prester John with Qatwan, although Yelü Dashi was no Christian; there were, however, Nestorian Christians among the subjects and vassals of the Qara Khitai.