The first historical references to the Turks appear in Chinese records of about 2000 BC. These records refer to tribes called the Hsiung-nu, an early form of the Western term Hun, who lived in an area bounded by the Altai Mountains, Lake Baikal, and the northern edge of the Gobi Desert and are believed to have been the ancestors of the Turks. Specific references in Chinese sources in the sixth century AD identify the tribal kingdom called Tu-Küe located on the Orkhon River south of Lake Baikal. The Khans (chiefs) of this tribe accepted the nominal suzerainty of the Tang dynasty. The earliest known example of writing in a Turkic language was found in that area and can be dated from about 730 AD.
Other Turkish nomads from the Altai region founded the Göktürk Empire, a confederation of tribes under a dynasty of Khans whose influence extended during the sixth to eighth centuries from the Aral Sea to the Hindu Kush in the land bridge known as Transoxania, i.e., across the Oxus River. The Göktürks are known to have been enlisted by a Byzantine emperor in the seventh century as allies against the Sassanians. In the eighth century some Turkish tribes, among them the Oguz, moved south of the Oxus River, while others migrated west to the northern shore of the Black Sea.