Dou Xian
After the new Protector General of the Western Regions Chen Mu was killed in 75 CE by allies of the Xiongnu in Karasahr and Kucha, the garrison at Hami was withdrawn. At the Battle of the Altai Mountains in 89 CE, Dou Xian defeated the Northern Chanyu, who retreated into the Altai Mountains. The Han forces, allied with the subjugated Southern Xiongnu, again defeated the Northern Chanyu twice in 90 CE and 91 CE, forcing him to flee west into Wusun and Kangju territories.