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
Between 130-121 BCE, Chinese armies drove the Xiongnu back across the Great Wall, weakening their hold on Gansu as well as on what is now Inner Mongolia, and finally pushed them north of the Gobi into central Mongolia. Following these victories, the Chinese expanded into the areas later known as Manchuria, Mongolia, the Korean Peninsula, and Inner Asia. The Xiongnu, once more turning their attention to the west and the southwest, raided deep into the Amu Darya valley between 73-44 BCE. The descendants of the Yuezhi and their Chinese rulers, however, formed a common front against the Xiongnu and repelled them.