After the establishment of the Tang Dynasty, the Turks in the north were the main external problems faced by the Tang Dynasty. The Tang army under the reign of Emperor Li Shimin was unmatched in battle, and at the same time, the Turks happened to have frequent civil strife, so the Tang-Turkic War presented a one-sided superiority of the Tang Dynasty. In the fourth year of Zhenguan, the Tang army destroyed the Eastern Turk Khaganate in one fell swoop and captured the southern region. In the 20th year of Zhenguan, the Tang army again made an expedition to northern Mobei and destroyed the Xueyantuo Khanate established by the Eastern Turks. At the same time, the Tang army also continued to march westward, defeating the Western Turk Khaganate continuously. By the first year of Emperor Gaozong's reign (650 AD), the Western TurkIc Che-nos khan was pacified by the Tang Dynasty, and the vast areas that were originally ruled by the Turkic Khaganate, including the southern part of the country, the northern part of the desert, and the western region, were all under the rule of the Tang Dynasty. The tang dynasty's martial arts in the north surpassed the Han Dynasty and reached the peak of the history of the Central Plains Dynasty.
In order to consolidate the newly conquered territories, the Tang Dynasty set up a large number of qiangfu prefectures in the north, and set up a capital to manage the surrendered Turks. During the Yonghui period, the Tang Dynasty established the two major capital protectorates of Yanran and Hanhai, which managed the northern and southern mo regions respectively, and set up a number of prefectures and governors' mansions, with the chiefs of various Turkic tribes as the governors and assassins. In the third year of Long Shuo, the Tang Dynasty adjusted the capital protectorate in the northern frontier, moved the Yanran capital protectorate to Huiyi, renamed it hanhai capital protectorate, and managed the northern part of the desert; moved the old Hanhai capital protectorate to the ancient city of Yunzhong and changed it to the capital protectorate in the south of the desert, and managed the governors of the southern part of the desert. At this point, the north and south of the Tang Dynasty desert formed a pattern of separate management of the two major capitals of Hanhai and Yunzhong.
In the first year of Lin De (664 AD), the Tang Dynasty changed the Yunzhong Capital Protectorate to Shan Yu Dadu Protectorate, and the Yin King Li Xulun as the Shan Yu Dadu Protector. The Tang Dynasty set up the Shan Yu Capital to better manage the unruly Turkic subordinates, which was a very difficult task that could not be performed by non-famous generals. Although Li Xulun, the Prince of Yin, served as the capital protector, he was only a "remote leader", and the person who was actually in charge of the affairs of the capital was Shi Xiaosiye, the governor of the capital.
Xiao Siye was a famous general of the Tang Dynasty, from a noble family, and his family belonged to the Lanling Xiao clan, one of the four noble families of the Southern Dynasty. The Lanling Xiao clan was a royal family of the Qi and Liang dynasties of the Southern Dynasty, and the number of prominent people developed into the Tang Dynasty, and the number of prime ministers reached 10. Xiao Siye's maternal aunt was Empress Xiao of the Sui Dynasty, who followed Empress Xiao into the Turks when he was a teenager and returned to the Tang Dynasty in nine years. His long experience living in turks gave him a deep understanding of Turkic customs and mountainous terrain, so the Tang court often put him in charge of Turkic affairs. In the twentieth year of Zhenguan, Xue Yantuo's army of Jumozhi went south to the barren valley, and Xiao Siye, who was then serving as a tongshi sheren, went to comfort him, and Jumozhi surrendered. In the second year of Xianqing, Emperor Gaozong of Tang issued an edict to attack the Western Turks, with Su Dingfang as the main commander and Xiao Siye as the deputy marshal, defeated the Turkic soldiers and horses, and the Turkic khan Ashina Helusi fled to Central Asia, and Xiao Siye led his troops in a deep pursuit, and finally captured it. In the first year of Long Shuo, Emperor Gaozong commanded Xiao Siye to lead an army against Hui. In the same year, Xiao Siye was appointed grand commander of the Xianbei Road March to fight against Tiele. It can be seen that most of Xiao Siye's personal experience is related to Turkic affairs, and as a Turkic communication within the Tang Dynasty, he did make great contributions to the stability of the Tang Dynasty's frontiers.
But it was such a famous general, but he was also late and failed to help the Tang Dynasty maintain its rule over the Turks. In the later period of Emperor Gaozong of Tang, the power of the imperial government was controlled by Wu Zetian, and Wu Zetian vigorously eradicated dissidents in order to consolidate his personal power, resulting in turmoil in the internal situation of the Tang Dynasty. At the same time, the frontiers of the Tang Dynasty were also unstable, and Tibet frequently invaded the Tang borders. In this situation, in October of the first year of the Reign of Theolu (679 AD), the Turkic Ashwin Fu and Fengzhi two ministries under the jurisdiction of the Capital Protectorate launched a rebellion, and Ashina Ni became a khan, and then received a response from the chiefs of the twenty-four states, and the number of rebel troops reached hundreds of thousands. As soon as the rebellion broke out, it immediately attracted the attention of the Tang Dynasty, and Xiao Siye, who was the governor of the Capital Protectorate of Shan Yu, together with the Right Leading Wei General Hua Dazhi and the Right Qianniu Wei General Li Jingjia, led the troops to suppress it.
At this time, although the internal affairs of the Tang Dynasty were chaotic, the Tang army led by Xiao Siye was still considerable in battle, and the record of repeated victories against the Turks over the years made him despise the Turks. The Tang army and the Turks won the initial battle, the rebels were defeated and retreated, and the Tang army took advantage of the victory to pursue. Unexpectedly, because the enemy was too light, the Tang army did not take much precautions when they camped at night, and were attacked by the Turks at night, and the camp was in chaos, "The dead are innumerable." Xiao Siye led the cavalry to defeat, and Hua Dazhi and Li Jingjia led the infantry to fight and retreated to the Capital Protectorate. In the end, the counterinsurgency war ended in failure.
After the defeat of the suppression of the Turkic rebellion, Emperor Gaozong of Tang and Xiao Siyezu were honored with the merits of sparing him death. However, Xiao Siye was still exiled to Guizhou, and Hua Dazhi and Li Jingjia were all dismissed from their official posts. Xiao Siye was deeply aware of his feelings, and participated in many crusades against Goryeo, Hui and Tiele, and had rich combat experience. However, the suppression of the Turkic rebellion was ultimately a tragic defeat. The Turkic rebellion in the first year reversed the history of the Tang Dynasty's repeated victories against the Turks, caused a major blow to the Tang Dynasty, and shook the Tang Dynasty's rule over the northern frontier, laying the foundation for the establishment of the Later Turkic Khaganate.