刘武周
Emperor Gaozu's reign was concentrated on uniting the empire under the Tang. Aided by Li Shimin (), whom he created the Prince of Qin, he defeated all the other contenders, including Li Gui, Dou Jiande, Wang Shichong, Xue Rengao and Liu Wuzhou. By 628, the Tang Dynasty had succeeded in uniting all of China. On the home front, he recognized the early successes forged by Emperor Wen of Sui and strove to emulate most of Emperor Wen's policies, including the equal distribution of land amongst his people, and he also lowered taxes. He abandoned the harsh system of law established by Emperor Yang of Sui as well as reforming the judicial system. These acts of reform paved the way for the reign of Emperor Taizong, which ultimately pushed Tang to the height of its power.