Tian Hongzheng
In winter 817, imperial forces under Li Su entered Zhangyi's capital Cai Prefecture () and captured Wu Yuanji, whom Emperor Xianzong subsequently executed. Wang, hearing of Wu's defeat, became fearful, and he sent his two sons Wang Zhigan () and Wang Zhixin () to Tian Hongzheng, offering them as hostages and further offering to surrender De and Di Prefectures to imperial control. With Tian interceding on Wang's behalf, Emperor Xianzong agreed, accepting Wang's submission and restoring his titles. De and Di were merged into Henghai Circuit. When Emperor Xianzong subsequently waged a campaign against Li Shidao, who made a similar offer to Emperor Xianzong but then reneged, Wang Chengzong's brother Wang Chengyuan suggested that he join the imperial campaign against Pinglu, but Wang Chengzong did not do so.