Late in Emperor Gaozu's reign, an intense rivalry developed between his two oldest sons, Li Jiancheng the Crown Prince and Li Shimin the Prince of Qin, as Li Jiancheng, while a capable general himself, was overshadowed by Li Shimin, who had destroyed Tang's major enemies Xue Rengao the Emperor of Qin, Liu Wuzhou the Dingyang Khan, Wang Shichong the Emperor of Zheng, and Dou Jiande the Prince of Xia. Li Jiancheng and a brother who supported him, Li Yuanji the Prince of Qi, once accused Li Shimin of crimes, and Emperor Gaozu, believing in the accusations, was set to punish Li Shimin, when Chen interceded for Li Shimin, pointing out his great contributions, and Emperor Gaozu did not punish Li Shimin.