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.
Five Barbarians
In their wake a power vacuum was left on the Mongolian steppes. The main contenders were the Southern Xiongnu, who inhabited a region to the south of the steppe and had now grown into a group of more than a hundred thousand herdsmen on the Xihe plain, the Xianbei, who lived in the east of the steppe residing on the plains of Manchuria, the Dingling, who originally dwelt on the banks of Lake Baikal and had already commenced trekking south into the steppes before Duo Xian destroyed the Northern Xiongnu, and the Wuhuan, who lived south of the Xianbei and were the weakest of the four.