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
Harold Walter Bailey proposed an Iranian origin of the Xiongnu, recognizing all the earliest Xiongnu names of the 2nd century BC as being of the Iranian type. This theory is supported by turkologist . Central Asian scholar Christopher I. Beckwith notes that the Xiongnu name could be a cognate of Scythian, Saka and Sogdia, corresponding to a name for Northern Iranians. According to Beckwith the Xiongnu could have contained a leading Iranian component when they started out, but more likely they had earlier been subjects of an Iranian people and learned from them the Iranian nomadic model.