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.
Han–Xiongnu War
In 73 AD, General Dou Gu and his army departed from Jiuquan and advanced towards the Northern Xiongnu, defeating the Northern Xiongnu and pursuing them as far as Lake Barkol before establishing a garrison at Hami. In 74 AD, Dou Gu retook Turfan from the Xiongnu. The Han campaigns resulted in the retreat of the Northern Xiongnu to Dzungaria, while Ban Chao was threatening and bringing the city-states at the Tarim Basin to submission under the Han empire once again. In 74 AD, the King of Jushi submitted to the Han forces under General Dou Gu as the Xiongnu were unable to engage the Han forces.