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.
Wusun
The Wusun originally lived between the Qilian Mountains and Dunhuang (Gansu) near the Yuezhi. Around 176 BCE the Yuezhi were raided by the Xiongnu, who subsequently attacked the Wusun, killing their king and seizing their land. The Xiongnu adopted the surviving Wusun prince and made him one of their generals and leader of the Wusun. Around 162 BCE the Yuezhi were driven into the Ili River valley in Zhetysu, Dzungaria, and Tian Shan, which had formerly been inhabited by the Saka (Scythians). The Wusun then resettled in Gansu as vassals of the Xiongnu. In 133–132 BCE, the Wusun drove the Yuezhi out of the Ili Valley and settled the area.