The Syr Tarduš (Chinese rendering Xueyantuo 薛延陀) was a branch of the Turkish federation of the Tölöš (Chinese rendering Tiele 鐵勒). They lived as pastoral nomads on the southern flanks of the Altai Range during the Sui 隋 (581-618) and Tang 唐 (618-907) periods and consisted of two parts, the Syr and the Tarduš. With the foundation of the khanate of the Turks (Chinese name Tujue 突厥) the various Turkic tribes became vassals of the Tujue. The Syr Tarduš were famous as elite cavalry of the Turkish troops. When the khanate of the Tujue fell into two parts, the Syr Tarduš became subjects of the Western Turks 西突厥.
In 605, under the reign of Nijuechuluo Khan 泥撅處羅可汗 the various Tölöš tribes rebelled against the Western Turks and elevated Yijingeleng 俟斤歌楞, a chieftain of the Qibi tribe 契苾, to the position of khan, with the title of Yiwuzhenmohe Khan 易勿真莫何可汗, while the Syr Tarduš made Yijinyishibo 俟斤乙失鉢 their leader, with the title of Yedie Khan 也咥可汗. This was the first federation of all Tölöš tribes, but it was not to last for long, for Shegui Qaghan 射匱可汗 was able to reunite the Western Turks, and again forced the Syr Tarduš into submission.
When the leader of the Western Turks, Tongyehu Qaghan 統葉護可汗, died in 628, the Turkish khanate was disturbed by a rebellion of the vassal tribes. Yinan 夷男, leader of the Syr-Tarduš, decided to move eastwards with 70,000 households. He crossed the Altai Range and so geographically united the western Syr-Tarduš people with those living in the Mongolian steppe. At that time the leader of the Eastern Turkish khanate, Jieli Khan 頡利可汗, oppressed the Turkish tribes so much that many of them decided to recognize Yinan as their leader. The Tang court decided to make use of this situation to get destroy the Eastern Turkish khanate and sent Qiao Shiwang 喬師望 as an envoy to Yinan in order to bestow him the title of Zhenzhu Pijie Qaγan 真珠毗伽可汗. This alliance between the Syr Tarduš and the Tang empire succeeded for in 630 the Eastern Turkish khanate fell apart.
As a result of this vacuum the northern steppe was now controlled by the Syr Tarduš. Yinan's court (in Chinese sources called ya 牙) was located at Mt. Yudujun 郁督軍. His khanate reached from the banks of River Erguna in the east to the Altai Range. The Tang court bestowed the Turkish leader Ashina Simo 阿史那思摩 the title of Yiminishuyilibi Khan 乙彌泥孰俟利苾 with the order to administrate all the various Turkish tribes south of the Gobi desert. The tribes of the Uyghurs 回紇, Bayegu 拔野古, Tongluo 同羅 and Pugu 僕骨 were vassals of Yiman. Historians call this phase the second federation of the Tölöš. Yinan's son Bazhuo 跋灼 (with the title of Jielijulixueshaduomi Khan 頡利俱利薛沙多彌可汗) adopted a much different strategy than his father. When Emperor Taizong 唐太宗 campaigned against the state of Goryo 高麗, Bazhuo led the Syr Tarduš southwards to attack the Tang empire, but he was badly defeated. This defeat, along with his oppressive rule, contributed to a rebellion of the various tribesleaders.
In 646 the chieftain of the Uyghurs, Tumidu 吐迷度, and the leaders of the Pugu and Tongluo killed Bazhuo in battle and annihilated his family. The rebels enthroned Yiman's older brother 咄摩支 as the new khan, yet the Tang court had decided to punish the Syr Tarduš. The generals Cui Dunli 崔敦禮 and Li Ji 李勣 defeated the nomad tribes and forced the Syr Tarduš into submission. The region and its inhabitants came under the administration of six first-class (fu 府) and seven ordinary (zhou 州) prefectures under the protectorate (duhufu 都護府) of Yanran 燕然. The Syr Tarduš lived in the prefecrued of Xidan 奚彈 and Qilian 祈連.