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.
Xiongnu
As a result of these battles, the Chinese controlled the strategic region from the Ordos and Gansu corridor to Lop Nor. They succeeded in separating the Xiongnu from the Qiang peoples to the south, and also gained direct access to the Western Regions. Because of strong Chinese control over the Xiongnu, the Xiongnu became unstable and were no longer a threat to the Han Chinese.
Ban Chao, Protector General (都護; "Duhu") of the Han dynasty, embarked with an army of 70,000 men in a campaign against the Xiongnu insurgents who were harassing the trade route now known as the Silk Road. His successful military campaign saw the subjugation of one Xiongnu tribe after another. Ban Chao also sent an envoy named Gan Ying to Daqin (Rome). Ban Chao was created the Marquess of Dingyuan (定遠侯, i.e., "the Marquess who stabilized faraway places") for his services to the Han Empire and returned to the capital Luoyang at the age of 70 years and died there in the year 102. Following his death, the power of the Xiongnu in the Western Regions increased again, and the emperors of subsequent dynasties were never again able to reach so far to the west.