Empress Cao
In 621, with Li Shimin (a son of Li Yuan, who had in 618 established Tang Dynasty as its Emperor Gaozu) attacking Wang Shichong the Emperor of Zheng, Dou, believing that if Tang destroyed Zheng, his own Xia state would be cornered, went to Wang's aid, but was defeated by Li Shimin at the Battle of Hulao and captured. His wife Empress Cao and a number of generals fled back to the Xia capital Ming Prefecture (洺州, in modern Handan, Hebei) and considered supporting an adoptive son of Dou Jiande as Prince of Xia and continuing to resist Tang, but at the urging of the official Qi Shanxing (齊善行), Xia forces were disbanded. Qi, Pei, and Empress Cao's brother Cao Dan (曹旦) then escorted her and surrendered to Tang.