窦建德
The faction led by Li Yuan eventually formed the Tang dynasty while Li himself became historically known as "Emperor Gaozu of Tang". Cheng Yaojin was appointed as a military officer under Li Yuan's second son, Li Shimin (the Prince of Qin). He fought for the Tang Empire against rival warlords such as Wang Shichong, Song Jingang () and Dou Jiande, who were either defeated or surrendered to Tang. Cheng Yaojin was enfeoffed as the "Duke of Su" () for his contributions in battle.