Xiongnu
The Xiongnu () were a confederation of nomadic peoples who, according to ancient Chinese sources, inhabited the eastern Asian Steppe from the 3rd century BC to the late 1st century AD. Chinese sources report that Modu Chanyu, the supreme leader after 209 BC, founded the Xiongnu Empire.
Proto-Mongols
The Xiongnu temporarily abandoned their interest in China and turned their attention westward to the region of the Altai Mountains and Lake Balkash, inhabited by the Yuezhi, an Indo-European-speaking nomadic people who had relocated from China's present-day Gansu as a result of their earlier defeat by the Xiongnu. Endemic warfare between these two nomadic peoples reached a climax in the latter part of the 3rd century and the early decades of the 2nd century BC; the Xiongnu were triumphant. The Yuezhi then migrated to the southwest where, early in the 2nd century, they began to appear in the Amu Darya Valley to change the course of history in Bactria, Iran, and eventually India.