刘黑闼
By winter 622, the only remaining major threat against Tang rule was Liu Heita, the Prince of Handong. He had been a Xia general, and rose against Tang after Li Yuan had executed Dou Jiande. He had been defeated by Li Shimin earlier in the year. Li Jiancheng's staff members Wang Gui and Wei Zheng argued to him that he needed some victories to establish his reputation, and Li Jiancheng volunteered to command the army against Liu Heita. Li Yuan sent Li Jiancheng to attack Liu, assisted by Li Yuanji. Around the turn of the year, Liu's forces were bogged down while attacking Tang's Wei Prefecture (魏州, in modern Handan, Hebei). Li Jiancheng and Li Yuanji engaged him at Guantao, crushing him. Liu fled north toward the Eastern Tujue, but was ambushed and captured by his own official Zhuge Dewei (諸葛德威), who delivered him to Li Jiancheng. Li Jiancheng executed Liu. China was by this point almost completely unified by Tang.