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
During the spring of 123 BC, General Wei Qing set off to Mongolia with an army to attack the Xiongnu; they marched back victorious to Dingxiang. Two months later, the Han army advanced towards the Xiongnu again, but this time the Xiongnu were prepared for the invasion by the Han forces. However, hereafter, due to the military expeditions that the Han empire undertook, the Xiongnu moved their capital and retreated to the far northern regions of the Gobi Desert.