The next ruler of Samarkand was Mohammad Khān[267] ibn Sulaymān, who in A.H. 503 (1109) successfully defended his capital against the attack of a large Turkish force under a certain Sāghir Beg. He held this post until his death, and apparently continued in his loyalty to Sanjar, who, as we have seen, ascended the throne of the Seljūks in 511. We are not told when he died, but Narshakhi says that his son Nasr Khān was killed during a revolt in Samarkand in A.H. 523 (1128). On the death of his father, Nasr’s son Mohammad Khān wrote to inform Sanjar of what had passed. Sanjar thereupon set out with a force to establish order in Samarkand, but when he approached the town Mohammad Khān sent him an insolent message that the Sultan would do well to retreat, inasmuch as he (Mohammad) had subdued his opponents. Sanjar was much incensed, and promptly invested the city. After a protracted siege he captured Samarkand and took Mohammad prisoner, A.H. 524 (1129). A new governor was now appointed, but he died two years later, when the reins of power were given to Mahmūd Khān, the son of Mohammad.[268] In the meanwhile another mighty host was advancing on Transoxiana; but before describing their progress we must retrace our steps and recount the downfall of the Ghaznavides and the rise of the great Seljūk dynasty of Persia. CHAPTER XVII THE GHAZNAVIDES AND THE RISE OF THE SELJŪKS The struggles between Mahmūd of Ghazna and Ilik Khān of Kāshghar continued till the year A.H. 401 (1010), when the latter, owing to a quarrel with his brother Toghān, was obliged to withdraw his troops, and a long period of peace ensued, with but slight interruptions, during which the Oxus continued to be regarded as the frontier of their respective realms. Before the actual downfall of the Sāmānides the province of Khwārazm,[269] which lay between the states of the Turkish Khāns and the Ghaznavides, had become practically independent. On the final overthrow of the Sāmānides, the Khwārazm Shāh,[270] as their ruler was called, had thrown in his fortunes with the Ghaznavides. In A.H. 407 (1017) the then ruler was murdered by rebels, whereupon Mahmūd marched into the country at the head of a large force and conquered it, setting up a governor of his own creation named Altuntāsh. Great difficulties attend an attempt to define the ethnographic affinities of the Turks. A similarity of language forces one to associate the Tartars of Southern Russia, the Turkomans of the Oxus countries, and the Uzbegs of Transoxiana. This race, in the broadest sense of the word, may be divided into three groups:-- (1) The Northern Turks, comprising the Siberian nomads, such as the Yakuts, etc. (2) The Eastern Turks, including those of Chinese Turkestān and the Uzbegs of Russian Turkestān, to whom are related the Tartars of the Crimea and the Volga.