?But the cost of the Xia army's defensive position shift was causing greater chaos. Li Shimin now decided to use his trump card. He personally led a thousand of the most elite Xuanjia cavalry, accompanied by Cheng Zhijie (that is, Cheng Yaojin), Qin Qiong and other powerful generals to launch a final violent attack on Dou Jiande's army. The Xuanjia troops rolled up their flags and waited until the cavalry charge penetrated the entire Xia Army's formation and reached near the cliff before unrolling the Tang Army's flag behind the Xia Army's formation. The morale of Dou Jiande's army was already low, and now he was even more frightened when he saw the flags of the Tang army flying behind his formation. At this time, the cavalry of the Tang Army, which was detouring from the flanks, had also arrived, and they attacked together with the Xuanjia cavalry. Dou Jiande's army quickly collapsed completely.

According to statistics, more than 3,000 Xia troops were directly killed in the Tang army's charge, and more than 50,000 Xia troops were captured by the Tang army. Li Shimin dismissed these prisoners that day and allowed them to return to their hometowns. Dou Jiande was stabbed by a spear and fled to Niukouzhu. Tang Chariot Generals Bai Turang and Yang Wuwei chased Dou Jiande, but Dou Jiande fell off his horse and was captured.

News of the defeat of Dou Jiande's army soon spread to Luoyang, and Wang Shichong, who was already exhausted, surrendered on June 4. The great victory of the Battle of Hulao Pass allowed the Tang army to defeat two powerful opponents in one battle. Coupled with the victory of the famous Tang army general Li Jing in the south, there was no suspense about the Tang Dynasty's unification of China. 3,500 elite cavalry (should also include the original garrison of Hulao Pass) defeated the 120,000-strong army. This classic example of cavalry in the early Middle Ages can be recorded in the annals of world military history, and is also the highest peak of Li Shimin's personal military career.