Nomadic empire
The Xiongnu were a confederation of nomadic tribes from Central Asia with a ruling class of unknown origin and other subjugated tribes. They lived on the Mongolian Plateau between the 3rd century BC and the 460s AD, their territories including modern day Mongolia, southern Siberia, western Manchuria, and the modern Chinese provinces of Inner Mongolia, Gansu, and Xinjiang. The Xiongnu was the first unified empire of nomadic peoples. Relations between early Chinese dynasties and the Xiongnu were complicated and included military conflict, exchanges of tribute and trade, and marriage treaties. When Emperor Qin Shihuang drove them away from the south of the Yellow River, he built the famous Great Wall to prevent the Xiongnu from coming back.
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.