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.
Oghuz Turks
During the 2nd century BC, according to ancient Chinese sources, a steppe tribal confederation known as the Xiongnu and their allies, the Wusun (probably an Indo-European people) defeated the neighboring Yuezhi and drove them out of western China and into Central Asia. Various scholarly theories link the Xiongnu to Turkic peoples and/or the Huns. The first usage of the word "Oghuz" appears to have been the title of "Oğuz Kağan", given in 220 BC to the Xiongnu king Modu Shanyu (or Mau-Tun), who founded the Xiongnu Empire. According to a controversial theory with few scholarly adherents, one transliteration of Yuezhi, as "Hu-chieh", may refer to the Turkic Uyghurs. However, the Yuezhi are widely believed to have spoken an Indo-European language or languages.