柔然
A branch of the Xianbei, the Rouran (also known as Nirun) were consolidated under Mugulyu. In the late 5th century, the Rouran established a powerful nomadic empire spreading generally farther north of Northern Wei. It was probably the Rouran who first used the title khan. The Rouran ruled Mongolia, eastern Kazakhstan, part of Gansu, northern Xinjiang, Inner Mongolia, parts of Northeastern China and southern Siberia. The Hephthalite Empire was a vassal state to the Rouran for 100 years. Shelun assumed the title of "Khagan" in 402 landmarking the establishment of the state of the Rouran Khaganate. The Tuoba waged long wars against the Rouran Khaganate. The Altai Turkics that were subjects of the Rouran revolted in 552 establishing the Turkic Khaganate. The Rouran Khaganate was finally defeated by the Turkics in 555. Part of the Rouran left the present territory of Mongolia. A number of historians maintain that they established the Avarian Kaganate between the river Danube and the Carpathian Mountains. The Rourans that stayed in Mongolia became the ancestors of the Tatar tribes. The Tatars and other Mongol tribes lived in the eastern part Mongolia during the Turkic period. Other Mongols that migrated east returned in the 8th century.