they were made up mostly of Turkic tribes that had been incorporated into the Mongol armies as the tribes were encountered in the Mongols' southward sweep. As these armies settled in Mawarannahr, they intermixed with the local populations which did not flee. Another effect of the Mongol conquest was the large-scale damage the soldiers inflicted on cities such as Bukhara and on regions such as Khorazm. As the leading province of a wealthy state, Khorazm was treated especially severely. The irrigation networks in the region suffered extensive damage that was not repaired for several generations. Many Iranian-speaking populations were forced to flee southwards in order to avoid persecution. Following the death of Genghis Khan in 1227, his empire was divided among his four sons and his family members. Despite the potential for serious fragmentation, Mongol law of the Mongol Empire maintained orderly succession for several more generations, and control of most of Mawarannahr stayed in the hands of direct descendants of Chaghatai, the second son of Genghis. Orderly succession, prosperity, and internal peace prevailed in the Chaghatai lands, and the Mongol Empire as a whole remained strong and united. But, Khwarezm was part of Golden Horde. Timur and Timurids In the early fourteenth century, however, as the empire began to break up into its constituent parts, the Chaghtai territory also was disrupted as the princes of various tribal groups competed for influence. One tribal chieftain, Timur (Tamerlane), emerged from these struggles in the 1380s as the dominant force in Mawarannahr. Although he was not a descendant of Genghis, Timur became the de facto ruler of Mawarannahr and proceeded to conquer all of western Central Asia, Iran, Asia Minor, and the southern steppe region north of the Aral Sea. He also invaded Russia before dying during an invasion of China in 1405. Timur initiated the last flowering of Mawarannahr by gathering in his capital, Samarqand, numerous artisans and scholars from the lands he had conquered. By supporting such people, Timur imbued his empire with a very rich Perso-Islamic culture. During Timur's reign and the reigns of his immediate descendants, a wide range of religious and palatial construction projects were undertaken in Samarqand and other population centers. Timur also patronized scientists and artists; his grandson Ulugh Beg was one of the world's first great astronomers. It was during the Timurid dynasty that Turkic, in the form of the Chaghatai dialect, became a