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.
Origin of the Huns
At the beginning of the twentiethcentury, German Sinologist Friedrich Hirth discovered passages in the Chinese annals that he believed proved the connection between the Huns and the Xiongnu. Hirth's work convinced many, and by the 1940s there was a general consensus among historians and archaeologists that the Xiongnu and the Huns were related. However, Otto J. Maenchen-Helfen showed conclusively that Hirth had misinterpreted the Chinese annals in 1945. Maenchen-Helfen also argued against the identification based on then-current archaeology and on ethnographic grounds. While he did not address the question in his most important work, "The World of the Huns" (1973), Maenchen-Helfen would go on to cast doubt on new theories that equated the Huns and the Xiongnu on the basis of their names in several articles. Maenchen-Helfen's skepticism was also taken up by prominent Eurasianist Denis Sinor.