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.
Army of the Han dynasty
In 71 BC, Chang Hui and two other generals led a force of 100,000 to aid the Wusun against the Xiongnu. The majority of the forces failed to find any Xiongnu, but Chang Hui successfully aided the Wusun in defeating a Xiongnu invasion. However the Xiongnu came back in winter and took many captives. On the way back across the Altai Mountains, the Xiongnu suffered heavy casualties from a sudden blizzard, devastating their army. The next year the Xiongnu were attacked on all sides by Wusun, Wuhuan, and the Han. One third of all Xiongnu died.