Ali ibn al-Athir
According to Kashgari, Yabaku chief Böke Budrach led a pagan coalition from Western Siberia or further east across the Irtysh river to wars against Islamic Kara-khanid khanate (comprising modern Western and Eastern Turkestan); Karakhanid heroic epics also mentioned these invasions, thwarted successfully by Karakhanids. According to Al-Utbi and Ali ibn al-Athir, the coalition's invasions began around the 1010s (or later in the 1030s) from the direction of "Ṣîn", i.e. Northern China. However, Budrach's coalition, which outnumbered the Karakhanid army, was still defeated by Toghan Khan (r. 998 - 1017/1018), who died shortly after his victory. Kashgari cited a witness, who related that Ghazi Arslan Tegin defeated the Yabaku-led coalition and captured Budrach.