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.
Proto-Mongols
The Donghu (or Tung Hu, the Eastern Hu), a proto-Mongol and/or Tunguz group mentioned in Chinese histories as existing as early as the 4th century BC. The language of the Donghu, unlike that of the Xiongnu, is believed by modern scholars to be proto-Mongolic. The Donghu were among the first peoples conquered by the Xiongnu. By the 1st century AD, the Donghu had split, along geographical lines in two: the proto-Mongolic Xianbei (Wade–Giles "Hsien-pei") in the north and the Wuhuan in the south. After the Xiongnu were driven back into their homeland by the Chinese (48 AD), the Xianbei (in particular) began moving (from apparently the north or northwest) into the region vacated by the Xiongnu.