Uokil (Ukil, Vokil, Augal) is one of Yuezhi tribes, defeated and displaced by the Hun's expansion in the 2nd century BC. Uokil may have been one of the two Yuezhi dynastic tribes. Traces of ethnonym "Uokil" are found in the East Mongolia and Manchuria territories in the Syanbi (Ch. 鲜卑 Xianbei), ancient Turkic, and Mongolian time.
Before the end of the 4th century BCE, the Yuezhi country (Chinese ngiw.at-tie) extended west from the northern bend of the Yellow River. At the very end of the 3rd century BCE, the Huns subjugated the northern states Hunüy, Tsüyshe, Dinlin, Gegun-Yenisei Kyrgyzes and Sinli-Sirs. Later, they conquered the Utsze/Augal state. The ancient Chinese transcription Hutsze (Utsze) reflect the original ethnonym Uokil. The first and initial point of Uokil migration to the west was the territory of E. Baikal and Great Khingan slopes. Later, Uokils united with a Nan Shan branch of the Yuezhi in their movement, initially to the Aral area, and then on to Bactria and Sogdiana. Probably, Uokils (Augals) participated in the storm of the region together with the Tochars and Sakaraukas.
The Chinese dynastic chronicle Hanshu, describing the events of 49 BCE, tells that the Hun shanyu Chjichji, in his western campaign, defeated a "small Hunnish state Hutsze in the north". In the 1st century BC Hanshu recorded that the Uokils lived in the Baikal area, next to the Dingling. That was Uokil's refuge after evacuating from the area west from the northern bend of Yellow River, where they had an independent kingdom prior to their defeat by the Huns in the middle of the 2nd century BCE. In the Baikal area, Uokils reorganized and temporarily again gained independence from the Huns, until the campaign of the Chjichji shanyu.
The defeat of Yuezhi by the Huns in the 172-164 BCE forced a migration of a significant part of the eastern Yuezhi from the Central Asia to the Middle Asia. The Yuezhi migration was not limited to the "storm" of Greco-Bactria, a main part of Yuezhi remained in the newly found lands, including the basin of the Syr-Darya and the Aral Sea area. In the 2nd century CE, at least three hundred years after the beginning of their migration, Ptolemy (VI, 12, 4) wrote about the Lower Syr-Darya:" ...near a section of Amu Darya in the north live Yati and Tocharians, below which live Augals". The Greek called Uokils "Augals".
In the Early Middle Ages, a Vokil clan was known as a dynastic clan that gave Danube Bulgaria four monarchs listed in the Namelist of Bulgarian Rulers (Nominalia). The Vokil clan was one of the dynastic clans whose ancestors "ruled on that side of Danube for 515 years with shaven heads". The first Bulgarian supreme Khan of the Vokil lineage listed in Nominalia is Kormisosh (r. 737–754), the last Umor (r. 766). The other dynastic clans of the Bulgarians were the Dulo clan of Attila, and Ermi clan of Kubrat (Kurbat) maternal uncle Organa, the Gostun (custodian) of the Nominalia. In the Middle Asia, the ethnonym Uokil left its trace in a name of a hero Vekil in the Oghuz epos "Kitab-i dedem Korkut".
At the same time during the Early Middle Ages, the Uokil tribal division of Oghuz Turks, known at that time as Tokuz Oguzes (Nine Oguzes, or Tribes), was another part of the "Utsze"-"Augals" Tocharian successors. In the Chinese sources the Uokil were known in rendition sitsze (γiei-kiet < Igil), in the middle of the 7th century they were located on the northern bank of the river Kheglench, i.e. Cloud Wagon of Keglen River. The text of the Uigur Eletmish-Kagan (d. 759) funeral monument referred to the "Igil people", using determinative qara - "blackness" (qara igil bodun, in the Mogoin Shine Usu monument, line 14). The identification qara bodun - "black folk" is pointing that the Middle Asian Uokil tribesmen of that time adopted the Manichaean creed. A century later, the Middle Asian Uokil tribe is mentioned in the 9th century Uiguro-Tibetan road guide as a tribe led by a strong leader Hi-kil-rkor-hir-kin (Igil kül-irkin), located next to another Yuezhi successor "Hi-dog-kas" tribe of Iduq-qash, a "sacred white jasper" of the Yuezhi "Jasper clan" Uti.
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