Prince of Zhao
For the next few years, the rivalry intensified, although during the meantime both Li Jiancheng and Li Shimin served as generals when the Eastern Göktürks made incursions. In 623, when the general Fu Gongshi rebelled at Danyang (, in modern Nanjing, Jiangsu), Emperor Gaozu briefly commissioned Li Shimin to attack Fu, but soon cancelled the order and sent Li Shimin's cousin Li Xiaogong the Prince of Zhao Commandery instead.