Military history of the Three Kingdoms
By the time of the Three Kingdoms period the Xiongnu had already ceased to be a major power. Their last stand as a steppe empire was in 89 when Dou Xian led an army of 45,000 and decisively defeated them at the Battle of the Altai Mountains. The Xiongnu Empire was replaced by a loose confederation of disorganized Xianbei tribes, who were nonetheless highly aggressive and proved problematic to their southern neighbors. A southern branch of the Xiongnu split off from their northern neighbors in 50 AD and continued to exist as a Han puppet state in Bing Province. However, in 188 the Xiuchuge clan rebelled against their Chanyu, Qiangqu, for sending troops to aid the Han against the rebels Zhang Ju and Zhang Chun. They replaced Qiangqu with his son Yufuluo, who's hold on power was tenuous, and he was ousted over a marquis of the Xubu clan. When the marquis of Xubu died the next year an elderly king became the nominal head of state without the title of Chanyu and the Southern Xiongnu ceased to exist as a coherent entity. In 216 the Xiongnu of the Ordos were settled but the region remained outside the jurisdiction of Cao Wei's administration.
Yueban
Between 155 and 166, the Xianbei or Syanbi (Ch. , Wade–Giles Hsien-pi, Hsien-pei), a former vassal tribe of the Xiongnu, united under Tian-Shih-huai conducted a series of campaigns against Northern Xiongnu, eventually defeating them and forcing them to flee west, which started a series of Xiongnu migrations (93 CE - circa 380 CE) westward to southern Siberia and Central Asia. (The Xiongnu have often been linked to the Huns that later invaded Europe from the Eurasian steppe, although the link has never been conclusively established. Likewise the Yueban of late antiquity have sometimes been known as the "Central Asian Huns".)