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.
Xiongnu
In 53 BC Huhanye (呼韓邪) decided to enter into tributary relations with Han China. The original terms insisted on by the Han court were that, first, the "chanyu" or his representatives should come to the capital to pay homage; secondly, the "chanyu" should send a hostage prince; and thirdly, the "chanyu" should present tribute to the Han emperor. The political status of the Xiongnu in the Chinese world order was reduced from that of a "brotherly state" to that of an "outer vassal" (外臣). During this period, however, the Xiongnu maintained political sovereignty and full territorial integrity. The Great Wall of China continued to serve as the line of demarcation between Han and Xiongnu.