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.
Turkic migration
Qin's campaign against the Xiongnu of 215 BCE kept the Xiongnu at bay, driving them out of and seizing the Ordos region. Problems re-emerged after the Qin Dynasty. The Xiong-nu attacked Shanxi of the Han in 201 BCE. Emperor Gaozu of Han bought them off with jade, silk and a Chinese wife for the Shanyu, or leader. Relations with the Xiongnu continued to be troubled and in 133 BC Emperor Wu of Han proceeded against them with 300,000 men. Eighty-one years and fourteen expeditions later in 52 BC the southern Xiongnu surrendered and the northern desisted from raiding. The Han Dynasty military expeditions continued near the frontier of China, in the Han–Xiongnu War, and in 89 AD the Xiongnu state was defeated and soon ended.