History of Mongolia
Although the Xiongnu finally had been split into two parts in AD 48, the Xianbei (or Hsien-pei in Wade–Giles) had moved (apparently from the east) into the region vacated by the Xiongnu. The Xianbei were the northern branch of the Donghu (or Tung Hu, the Eastern Hu), a proto-Mongol group mentioned in Chinese histories as existing as early as the 4th century BC. The language of the Donghu is believed to be proto-Mongolic to modern scholars. The Donghu were among the first peoples conquered by the Xiongnu. Once the Xiongnu state weakened, however, the Donghu rebelled. By the 1st century AD, two major subdivisions of the Donghu had developed: the proto-Mongolic Xianbei in the north and the Wuhuan in the south.
Ancient history
The Huns left practically no written records. There is no record of what happened between the time they left Mongolian Plateau and arrived in Europe 150 years later. The last mention of the northern Xiongnu was their defeat by the Chinese in 151 at the lake of Barkol, after which they fled to the western steppe at Kangju (centered on the city of Turkistan in Kazakhstan). Chinese records between the 3rd and 4th centuries suggest that a small tribe called Yueban, remnants of Northern Xiongnu, was distributed about the steppe of Kazakhstan.