Han dynasty
To the north of China proper, the nomadic Xiongnu chieftain Modu Chanyu (r. 209–174 BC) conquered various tribes inhabiting the eastern portion of the Eurasian Steppe. By the end of his reign, he controlled Manchuria, Mongolia, and the Tarim Basin, subjugating over twenty states east of Samarkand. Emperor Gaozu was troubled about the abundant Han-manufactured iron weapons traded to the Xiongnu along the northern borders, and he established a trade embargo against the group. In retaliation, the Xiongnu invaded what is now Shanxi province, where they defeated the Han forces at Baideng in 200 BC. After negotiations, the "heqin" agreement in 198 BC nominally held the leaders of the Xiongnu and the Han as equal partners in a royal marriage alliance, but the Han were forced to send large amounts of tribute items such as silk clothes, food, and wine to the Xiongnu.
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).