"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 33 of this book.


The Qara-Khitays, having imposed their over lordship on the Idiquts, the Qarakhanids and the Khorezmshahs (see map 15), left these dynasties in place as their tributaries. Of the history of the Eastern Qaghanate during this period very little is known. As to the Western Qaghanate, it was plagued by wars with the rebellious Qarluq nomads in the Zerafshan valley; in the course of these wars the qaghans won some major battles, of which, however, none was decisive. In the 1160s the Western Qarakhanids, with the support of the Qara-Khitays, conquered Balkh. From 1178-79 the throne of Samarqand was occupied by the members of the Ferghana line of the Qarakhanid clan, who adopted the title “Great Sultan of Sultans.”
However, in reality in the second half of the 12th century much of the Western Qaghanate was divided into a number of independent principalities, with three of them in Ferghana (with centers in Uzgend, Kasan, and Marghinan), one in Shash (with a center in Benaket), and others in Otrar, Wakhsh (in the 1180s), and possibly Termez and Chaghaniyan.
Bukhara was ruled, from the first years of the 12th century, by the Burhanids, a dynasty of religious dignitaries
with the title of sadr, installed there by Sultan Sanjar; they were the immediate vassals of the Seljuks, not of the Qarakhanids. After the Qara-Khitay conquest, the Sadrs became representatives of the Gürkhans and collected the land tax in Bukhara for them.
The much-weakened Western Qaghanate could not withstand the pressure of two new rising powers, the Ghurids from the south and the Khorezmshahs from the west