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
However, the eastern part of north China came under the control of a rebel Xiongnu-Han general of Jie ancestry named Shi Le. Liu Yao and Shi Le fought a long war until 329, when Liu Yao was captured in battle and executed. Chang'an fell to Shi Le soon after, and the Xiongnu dynasty was wiped out. North China was ruled by Shi Le's Later Zhao dynasty for the next 20 years.