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
The Xiongnu-Hun hypothesis originated with the 18th-century French historian Joseph de Guignes, who noticed that ancient Chinese scholars had referred to members of tribes associated with the Xiongnu by names similar to "Hun", albeit with varying Chinese characters. Étienne de la Vaissière has shown that, in the Sogdian script used in the so-called "Sogdian Ancient Letters", both the Xiongnu and Huns were referred to as γwn ("xwn"), indicating that the two were synonymous. Although the theory that the Xiongnu were precursors of the Huns known later in Europe is now accepted by many scholars, it has yet to become a consensus view. The identification with the Huns may be either incorrect or an oversimplification (as would appear to be the case with a proto-Mongol people, the Rouran, who have sometimes been linked to the Avars of Central Europe).