After the Sui Dynasty Emperor Yang Guang ascended the throne, Li Yuan served as the Taishou of the two counties, and was later summoned as the Junior Inspector of the Palace and the Wei Wei Shaoqing. Li Yuan was promoted to the post of Retainer of Taiyuan, and Li Yuan became the highest military and political governor in the Taiyuan region. At the end of the Sui Dynasty, Li Yuan had already established some foundations for himself because of his inextricable relationship.
During Yang Guang's reign, he has been outside the city, overhauling the canal, the people's life is not good, and the peasant uprisings are continuous. Li Yuan, seeing that the world was in chaos, provoked an uprising with his second son Li Shimin, and quickly recalled his eldest son Li Jiancheng, and his third son, Li Yuanji, while sending Liu Wenjing as an envoy to the Turks, asking Bi Khan to send troops to help, while recruiting troops.
At that time, among the peasant rebel armies, one of the Wagang armies was the strongest, and as early as the sui II Yang Guang's ascension to the throne, Qu Rang gathered in WagangZhai to revolt, and Wang Bodang, Shan Xinxiong, Xu Shiji, and so on joined in, and the number reached a million when the largest number was reached. Later, infighting, Li Mi killed Qu Rang, and the strategy advocated was also wrong, and eventually the army was defeated. After the Wagang army was defeated by Yu Wenhua and Wang Shiyun, the famous generals of Wagang defected to Li Yuan, among whom the military commander Xu Shijie, the general Qin Qiong, and Cheng Yaojin became the famous generals of the early Tang Dynasty.
In the same year that Wagang was defeated, Yang Guang was killed by the rebels, and Li Yuan took advantage of the situation to force Yang You to pass the throne to him and establish the Tang Dynasty, which was the historical Tang Gaozu Li Yuan.