they made the Karakhanids a vassal state. The Seljuks dominated a wide area from Asia Minor, Iran, Iraq, and parts of the Caucasus, to the western sections of Transoxiana, in Afghanistan, in the eleventh century. The Seljuk Empire then split into states ruled by various local Turkic and Iranian rulers. The culture and intellectual life of the region continued unaffected by such political changes, however. Turkic tribes from the north continued to migrate into the region during this period. The power of the Seljuks however became diminished when the Seljuk Sultan Ahmed Sanjar was defeated by the Kara-Khitans at the Battle of Qatwan in 1141. In the late twelfth century, a Turkic leader of Khorazm, which is the region south of the Aral Sea, united Khorazm, Transoxiana, and Iran under his rule. Under the rule of the Khorazm shah Kutbeddin Muhammad and his son, Muhammad II, Transoxiana continued to be prosperous and rich while maintaining the region's Perso-Islamic identity. However, a new incursion of nomads from the north soon changed this situation. This time the invader was Genghis Khan with his Mongol armies. As Turks began entering the region from the north, they established new states starting from the 11th century and began to change the demographics of the region. After a succession of states dominated the region, in the twelfth century, Transoxiana was united in a single state with Iran and the region of Khwarezm, south of the Aral Sea. In the early thirteenth century, that state was invaded by Mongols, led by Genghis Khan. Under his successors, Iranian-speaking communities were displaced from some parts of Central Asia. Under Timur (Tamerlane), Transoxiana began its last cultural flowering, centered in Samarqand through the Timurid Renaissance. After Timur the state began to split, and by 1510 Uzbek tribes had conquered all of Central Asia. Mongol period The Mongol invasion of Central Asia is one of the turning points in the history of the region. The Mongols had such a lasting effect because they established the tradition that the legitimate ruler of any Central Asian state could only be a blood descendant of Genghis Khan. The Mongol conquest of Central Asia, which took place from 1219 to 1225, led to a wholesale change in the population of Mawarannahr. The conquest quickened the process of Turkification in some parts of the region because, although the armies of Genghis Khan were led by Mongols,