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
Coincidentally, the Southern Xiongnu were plagued by natural disasters and misfortunes – in addition to the threat posed by Punu. Consequently, in 50 AD, the Southern Xiongnu submitted to tributary relations with Han China. The system of tribute was considerably tightened by the Han, to keep the Southern Xiongnu under control. The "chanyu" was ordered to establish his court in the Meiji district of Xihe commandery and the Southern Xiongnu were resettled in eight frontier commanderies. At the same time, large numbers of Chinese were also resettled in these commanderies, in mixed Han-Xiongnu settlements.
Economically, the Southern Xiongnu became reliant on trade with the Han.