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.
History of the Han dynasty
The Eastern-Han court colonized and periodically reasserted the Chinese military presence in the Western Regions only as a means to combat the Northern Xiongnu. Han forces were expelled from the Western Regions first by the Xiongnu between 77–90 CE and then by the Qiang between 107–122 CE. In both of these periods, the financial burdens of reestablishing and expanding western colonies, as well as the liability of sending financial aid requested by Tarim-Basin tributary states, were viewed by the court as reasons to forestall the reopening of foreign relations in the region.