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The Xueyantuo were an ancient Tiele Turkic people and khaganate in central/northern Asia who were at one point vassals of the Gokturks, later aligning with China's Tang Dynasty against the Eastern Gokturks. The Xueyanto homeland is near the Xueyanhe River (薛延河江/偰輦河江, Selenga River), so their tribe's name is Xueyantuo (薛延陀), Chinese Han characters underwent considerable changes according to changes in Chinese dynasties, so the tribe is variously known as Xueyantuo, Xueyanhe, Xienianhe, Selenga, etc.
The Xue 薛 appeared earlier as Xinli 薪犁 in Sima Qian's Records of the Grand Historian, vol. 110 but were not referred to again until the 7th century. Golden (2011) proposed that 薛 Xue's Old Turkic form Sir derived from Sanskrit Śrī "fortunate, auspicious" Yantuo 延陀 was identified with Tarduš, one of two divisions, besides Töliš, of the short-lived Xueyantuo Qaghanate, by Western Orientalists (like Vilhelm Thomsen) who considered Töliš and Tarduš to be tribal names. The ethnonym is thus reconstructable as Syr-Tardush. However, Chinese scholars viewed Töliš and Tarduš as names of political organizations or districts: for example, Cen Zhongmian viewed the Töliš-Tarduš division as east–west whereas Wang Jingru, citing New Book of Tang, viewed Töliš-Tarduš as north–south.
H.W. Haussig (1953: 342), apud Golden (1992), disputed the Yantuo-Tarduš connection and suggested that Chinese 薛延陀 Xueyantuo and Greek Σηρίνδα Sirinda reflected one same underlying ethnonym. Meanwhile, Sergey Klyastorny (2003:305), apud Golden (2018), proposed that Xueyantuo transcribed *Sir-Yamtar; in contrast to the tribal name Sir, [Ïšβara] Yamtar appeared as a personal name of one companion of Kül Tigin, mentioned the eponymous inscription in his memory.
Initially the Xue and the Yantuo were two separate tribes. Tongdian states that: "Xueyantuo is a splinter tribe from Tiele. In the time of Former Yan [emperor] Murong Jun, Xiongnu Shanyu Helaitou led his tribe, numbering 35,000, to come surrender. Yantuo are probably their descendants. With the Xue tribe [Yantuo] live intermixed. Thus the appellation Xueyantuo. The Khagan clan's surname is Yilitu. For generations they have been a strong nation." The rulers of Xueyantuo claimed to be originally named Xue (薛/偰), and that the name of the tribe was changed to Xueyantuo after the Xue defeated and merged the Yantuo into their tribe.
In 605, Xueyantuo were attacked by the Western Türkic Chuluo Khagan. Consequently, they abandoned the Western Turks and established their own Kaganate under a leadership of Qibi tribe's Yağmurčin Bağa-Qağan, retaining the control and income from the Turfan segment of the Silk Road. Later, Xueynatuo leader Yshbara was installed as a lesser Kagan Yetir (yeti er "seven tribes"). In the 610, Shekui (r. 610-617) ascended to the Western Turkic throne, both rulers renounced their Kagan ranks and rejoined the Western Türkic Kaganate. The next Western Türkic Tong-Yabgu-Kagan (r. 617-630) annexed all seven tribes of the Xueyantuo-headed Tiele confederation, which also included Uighur, Bayïrku, Ădiz, Tongra, Bugu and Barsil tribes. in 627 Xueyantuo leader led his tribes into the territory of the Eastern Türkic Kaganate, defeated the main force of the Kaganate led by the son of the reigning Illig Qaghan, Yukuk Shad, and settled in the valley of river Tola in the Northern Mongolia. After the victory, Uighur leader Yaoluoge Pusa assumed a title huo xielifa (Chinese: 活頡利發 kat-elteber) and split from the confederation, and in 629 the Xueyantuo Yinan-erkin declared himself Inčü Bilge-Khagan of a new Xueyantuo Kaganate.
This Xueyantuo Kaganate was quickly recognized by the Tang Empire, as a counterweight against its enemy Eastern Türkic Kaganate. "Raising Yi'nan on Kagan throne was done under pressure from the Tang court interested in stripping El-kagan of the rights to the supreme power in the huge region, and also in final dismemberment of the Türkic state, a source of many conflicts on their northern borders."  Xueyantuo provided military service by assisting the Tang Empire against the Tatars in the 630s. The Xueyantuo's vast khaganate spanned from the Altai Mountains to the Gobi desert.
On March 27, 630, the Xueyantuo allied with the Chinese to defeat the Eastern Qaghanate in the Yin Mountains. Illig Qaghan escaped, but was handed over to the Chinese by his subordinate qaghan on May 2.
After Eastern Gokturk Illig Qaghan Ashina Duobi was defeated by Tang in 630, the Xueyantuo effectively took over control of the Eastern Gokturks' former territory, at times submissive to the Tang and at times warring with the Tang and the subsequent khan of the Eastern Gokturks that Tang supported, the Qilibi Khan Ashina Simo.
In 632 the Xueyantuo repulsed an army of Si Yabgu Qaghan from the Western Qaghanate, then subjugated the Qarluq at the Ulungur and Irtysh River, and then the Yenisei Kyrgyz tribes. In 634 one of their rivals, Dubu Qaghan (Ashina Shier), son of Chuluo Khan, who ruled much of the eastern half of the Western Qaghanate, was eliminated before escaping to China.
After that they maintained a friendly relationship with the Chinese until 639, when a raid on the Chinese capital was planned by the Gökturks under Ashina Jiesheshuai (阿史那结社率), who had been disparaged by the Chinese emperor. He allied with his nephew Ashina Heluohu (阿史那贺逻鹘), choosing him as the leader of the raid on May 19. They were unsuccessful and over 40 rebels were executed. Heluohu was spared and expelled to the far south.
After this incident, an arraignment was made on August 13. A deportation of all Goktürks north of Ordos was carried out, in an attempt to restore the puppet Eastern Qaghanate as a barrier against the Xueyanto, in an attempt to distract them from the territorial competition in the west.
Among the Göktürk nobles, Ashina Simo was selected as the qaghan (Qilibi Khan) with his capital at the border. The plot failed, as he was unable to gather his people, many of his tribesmen having escaped to the south by 644 after a series of unsuccessful incursions by the Xueyantuo supported by the Chinese. Defeats by the advancing Chinese had made their tribal allies lose confidence in them. The crisis deepened the next year when a coup d'état took place within the clan.
On August 1, 646, the Xueyantuo were defeated by the Uyghur (Huihe, 回纥) and the Chinese. The Xueyantuo's Duomi Khan, Bazhuo, was killed by the Uyghur. A Tang army led by the general Li Daozong, the Prince of Jiangxia, crushed the Xueyantuo forces. The last Xueyantuo khan, the Yitewushi Khan Duomozhi, surrendered. Their remnants were destroyed two years later, on September 15. Yantuo possibly re-appeared later as Tardush during Kul Tigin's lifetime
Xueyantuo's relationship with the later Shatuo Turks is contested. The epitaph of Shatuo leader Li Keyong states that his clan's progenitor was "Yidu, Lord of the Xueyantuo country, an unrivaled general" (益度、薛延陀國君、無敵將軍). However, Chinese chroniclers also traced the Shatuo's origins to a Tiele chief named *Bayar (拔也 Baye) ~ *Bayïrku (拔也古 Bayegu) or Western Turkic Chigils (處月 Chuyue)
The surname of Xueyantuo's khans is uncertain, although modern Chinese historian Bo Yang lists their surname as "Yishi" in his edition (also known as the Bo Yang Edition) of the Zizhi Tongjian, but without citing a source. It is possible that Bo was influenced by the Tongdian, which refers to the Xueyantuo surname as Yilitu 壹利吐, Yiliduo 一利咄 as in Cefu Yuangui, Yilidie 壹利咥 as in New Book of Tang. Li Keyong's epitaph also records his alleged Xueyantuo ancestor's name as Yidu 益度.
According to Cen Zhongmian, the aforementioned names are related to a variant of elteris. Duan Lianqin asserted that the name Yishibo (Yiedie Khan) can also be read interchangeably as Yedie (也咥). The Zizhi Tongjian, in the original, referred to one ethnic Xueyantuo general named Duomo, possibly the Yitewushi Khan (after he became a Tang general) by the family name of Xue—although the Tang Huiyao indicated that it was not the same person, as it indicated that the Yitewushi Khan died during Emperor Taizong's reign.