Reign of Genghis Khan
By 1221, the whole of Central Asia fell to the reign of Genghis Khan. Cities were destroyed, irrigation systems crushed, hundreds of thousands of people were killed and taken prisoner of war.
Following the death of Genghis Khan in 1227, Central Asia along with the area of Seven Rivers, and Eastern Turkestan made up the so-called ulus, or the land possessions ruled by the sovereign. As such, was appointed the second son of Genghis Khan, Chagatai, but the ulus was actually led by Makhmud Yalavach.
The decade of the 40s of the 14th century saw the disintegration of the Chagatai ulus into several states. The split and internal wars became worse and cruder. Taking advantage of the situation, in the second half of the 14th century, the great Amir Temur (Tamerlane) came on the scene (1336-1405).