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 Mongolia
The founder of the Xiongnu empire was Toumen. He was succeeded violently by his son Modu Shanyu, who then conquered and unified various tribes. At the peak of its power, the Xiongnu confederacy stretched from Lake Baikal in the north to the Great Wall in the south and from the Tian Shan mountains in the west to the Greater Khingan ranges in the east. In the 2nd century BC the Xiongnu turned their attention westward to the region of the Altai Mountains and Lake Balkash, inhabited by Indo-European-speaking nomadic peoples, including Yuezhi (Yüeh-chih in Wade–Giles), who had relocated from China's present-day Gansu Province as a result of their earlier defeat by the Xiongnu. Endemic warfare between these two nomadic peoples reached a climax in the latter part of the 3rd century and the early decades of the 2nd century BC; the Xiongnu were triumphant. The Yuezhi then migrated to the southwest where, early in the 2nd century, they began to appear in the Oxus (the modern Amu Darya) Valley, to change the course of history in Bactria, Iran, and eventually India.