Chizhishizhuhou Chanyu
The southern Xiongnu were a branch of the eastern Xiongnu that followed the rebellious pretender Huhanye and in 51-53 BC moved en masse within the Han borders under protection of Chinese. Since the times of Huhanye, the status of the southern Xiongnu was loyal allies of the Han Dynasty. The southern Xiongnu enjoyed material support of the old "heqin" treaty, and in return guarded the Chinese northern borders and participated in the Chinese external and internecine conflicts as long as the Chinese court respected their independence. However, when the Han imperial court attempted to appoint an ineligible for the crown Western Jükü-Prince Yufuluo from ineligible Right Wing as a Chanyu, instead of respecting the traditional election, the southern Xiongnu dissented and elected a lawful alternate Hyuibu Gudu-heu. Later they expelled Yufuluo, who had to seek safety in exile at the Han imperial court.
Han–Xiongnu War
In 25 AD, Liu Xiu was established as Emperor Guangwu, restoring the Han throne after a usurpation by the Han official Wang Mang, thus initiating the Eastern Han period. During his reign, the Han empire began to abandon its offensive strategy against the Xiongnu, which allowed the latter to frequently raid the northern frontier. It resulted in large migrations southwards, which led to the depopulation of the frontier regions. During the Eastern Han period, various nomadic peoples were resettled in these frontier regions, serving the Han empire as cavalry against the Xiongnu. With his primary focus still towards the interior of the empire, Emperor Guangwu declined several requests from the western states to reestablish the office of Protector-General of the Western Regions. Early in Emperor Guangwu's reign, King Kang of Yarkand united neighboring kingdoms to resist the Xiongnu. At the same time, he protected the Han officials and people of the former Protector-General, who were still left behind after Wang Mang's reign. In 61 AD, Yarkand was conquered by Khotan and the western states fell in conflict with each other. Taking this opportunity, the Northern Xiongnu recovered their control over the Western Regions, which threatened the security of the Hexi Corridor. In 73 AD, General Dou Gu was sent on a punitive expedition to the Xiongnu and inflicted them a considerable defeat. Immediately, the fertile lands of Hami (Yiwu) was reoccupied and an agricultural garrison established. The next year (74 AD), he expelled the Xiongnu from Turfan and reoccupied the state. The recovery of Hami and Turfan facilitated the reestablishment of the Protector-General, since these important locations were key points to control the Western Regions.