It was during his tenure of office that the Kara-Khitāys began to make their inroads westwards. The empire of the Kara-Khitāys had been founded by the last prince of the Kitan or Liao dynasty,[303] whose name was Ye-liu Ta-shi.[304] On the destruction of that line by the Kin dynasty[305] in A.D. 1123, Ye-liu Ta-shi, with a following of some two hundred men, passed into the country lying to the north-west of Shen-si,[306] where he was joined by numbers of Turks. He now set out in a westerly direction and carried all before him. He conquered Kāshghar, Yarkand, Khotan, and Turkestān, and at the beginning of A.D. 1124 or 1125 he reached Ki-rh-man.[307] Here all his officers assembled and proclaimed him emperor, whereupon he assumed the title of _Gūr-Khān_, or “Universal Lord.” Mahmūd, the Uïghūr Khān mentioned above,[308] was driven into Transoxiana, which shortly after became tributary to the Kara-Khitāys. Ye-liu Ta-shi, whose dominions reached from the Gobi to the Oxus, and from the mountains of Tibet to Siberia, now fixed his residence at Balāsāghūn. Towards the end of Kutb ed-Dīn’s rule they advanced so far into Transoxiana that the Grand Ewer-bearer sent an army of 100,000 men to oppose them.[309] He, however, suffered a crushing defeat, and the prince of the Kara-Khitāys, after imposing tribute on his vanquished enemies, returned to Kāshghar, which now became his capital.[310] Soon after his deliverance from these barbarians Kutb ed-Dīn died,[311] and was succeeded by his son Atsiz. For many years the latter remained at the court of Merv, fulfilling the office of Grand Ewer-bearer to Sultan Sanjar; and so great was his influence with the Seljūk prince that he made himself many enemies at court, and on this account he asked permission to proceed to Khwārazm, which was then suffering from anarchy. In spite of the warnings of his ministers, Sanjar allowed Atsiz to depart. As soon as the governor reached his province he rose in open revolt against his master, who was compelled to march against his too powerful vassal.[312] But the rebels were no match for the troops of Sanjar, who utterly defeated them.[313] The province was restored to obedience, and Sulaymān Shāh, Sanjar’s nephew, was appointed as its governor.[314] No sooner had Sanjar reached his capital than Atsiz, collecting the scattered remnants of his army, proceeded to attack Sulaymān Shāh. This latter, with whom Sultan Sanjar had left but a few troops, deeming resistance useless, fled to his uncle, and thus the whole of Khwārazm again fell into the hands of Atsiz. [Illustration: MAUSOLEUM OF SULTAN SANJAR, OLD MERV]