 Later, in 620 and 621, he followed Li Shimin in his campaign against Wang Shichong the Emperor of Zheng, at the end of which Li Shimin defeated not only Wang, but Dou Jiande as well.After Dou's defeat, the Princess Nanyang, who had become a Buddhist nun, headed back from the Xia capital Ming Prefecture (洺州, in modern Handan) to Chang'an, and she happened to encounter Yuwen Shiji at Luoyang.Yuwen Shiji wanted her back as his wife, but she refused, stating to him, "My clan and yours have great enmity.