The Xijias were one of the northern ethnic groups in the Tang Dynasty. They were active in the upper reaches of the Jianhe River (now the Yenisei River). They were the ancestors of the Kirgiz people and the Kyrgyz people in Central Asia in what is now Xinjiang, China. In the Western Han Dynasty, Xiugasi first appeared in the annals of Chinese history under the name of Jiankun. After the Wei, Jin, and Sui and Tang dynasties, Xijiasi established contact with the Tang Dynasty. In the fifth year of Emperor Wenzong's reign (840), the Xijias defeated the Uighur Khanate that ruled Mobei and forced the remaining Uighurs to move westward, which had a major impact on the history of the Mongolian Plateau and even Central Asia. The history of the ancient Xijiasi has both the general characteristics of the northern grassland peoples and its own characteristics: Politically, the Xijiasi has a complex social structure, with multiple official systems of northern ethnic groups and Central Plains dynasties coexisting in parallel; economically, the Xijiasi is a mixed economy in the forest-steppe transition zone, with agriculture, animal husbandry, commerce, and handicrafts all developing, and it is deeply involved in the development of the Prairie Silk Road. Trade activities; militarily, Higas fought against tribal regimes such as Turks, Uighurs, and Tubos, and defeated the Mobei Uighurs in 840, shocking the interior of Asia; culturally, the handed down Yenisey inscriptions show that Higas used ancient Turkic characters, and the calendar used both Turkic and Central Plains. In short, the history of Higas in the Tang Dynasty reveals the complex characteristics of its culture. The Tang Dynasty was the most important stage in the historical development of the Xijiasi nation. The Central Plains dynasty with which they had direct contact for the first time, entered the Tang Dynasty during the reign of Emperor Taizong of the Tang Dynasty and was granted the title of Governor of Jiankun, and resumed contact with the Tang Dynasty during the Wuzong Dynasty of the Tang Dynasty. In addition, the Xijiasi also established their own tribe's khanate for the first time during this period, and competed with the Northern Uighur Khanate in the Momo, which shocked the grasslands and the Central Plains. Whether it is in the history of this nation or the history of East Asia as a whole, the history of the Tang Dynasty Xijiasi is of great significance.
