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 Donghu (or Tung Hu, the Eastern Hu), a proto-Mongol and/or Tunguz group mentioned in Chinese histories as existing as early as the 4th century BC. The language of the Donghu, unlike that of the Xiongnu, is believed by modern scholars to be proto-Mongolic. The Donghu were among the first peoples conquered by the Xiongnu. By the 1st century AD, the Donghu had split, along geographical lines in two: the proto-Mongolic Xianbei (Wade–Giles "Hsien-pei") in the north and the Wuhuan in the south. After the Xiongnu were driven back into their homeland by the Chinese (48 AD), the Xianbei (in particular) began moving (from apparently the north or northwest) into the region vacated by the Xiongnu.