窦建德
In 621, with Wang Shichong's state of Zheng under attack by the Tang general Li Shimin the Prince of Qin (the eventual Emperor Taizong) and in desperate straits, Dou Jiande believed that if Zheng were destroyed by Tang, his own Xia state would be cornered. He therefore launched his army, seeking to save Zheng's capital Luoyang. Li Shimin engaged him at the Battle of Hulao, and Dou was captured. Wang then surrendered. The Xia forces considered continuing to resist, but under the leadership of the official Qi Shanxing (), they surrendered Xia territory to Tang.