with Emperor Gaozu's favored young concubines than Li Shimin did (as their mother Duchess Dou had died before Tang's establishment), and those concubines helped rehabilitate Li Jiancheng's standing before Emperor Gaozu, causing him to no longer consider making Li Shimin crown prince instead, as he considered at one point. By winter 622, Liu Heita posed the only remaining major threat against Tang rule. At the suggestion of his staff members Wang Gui and Wei Zheng, who argued that Li Jiancheng needed some victories himself to establish his reputation, Li Jiancheng volunteered to command the army against Liu Heita. Emperor Gaozu thus sent Li Jiancheng, assisted by Li Yuanji. Around the new year 623, with Liu's forced bogged down while attacking Tang's Wei Prefecture (, in modern Handan, Hebei), Li Jiancheng and Li Yuanji engaged him at Guantao (, in modern Handan as well), crushing him. Liu fled north toward the Eastern Turks, but was ambushed and captured by his own official Zhuge Dewei (), who delivered him to Li Jiancheng. Li Jiancheng executed Liu. Around the same time, Xu was killed in flight. Meanwhile, Lin Shihong the Emperor of Chu, who had one point controlled modern Jiangxi and Guangdong, had died, and his followers scattered. China was by this point completely unified by Tang except for the domain of Liang Shidu the Emperor of Liang, who controlled modern northern Shaanxi and western Inner Mongolia, although, with Li Fuwei at Chang'an, Fu Gongshi rebelled in 623 and declared himself the Emperor of Song. Fu's rebellion, however, was quelled by Li Xiaogong in 624. Meanwhile, the rivalry between Li Jiancheng and Li Shimin intensified. In 624, Li Jiancheng requisitioned a number of soldiers from the general Li Yi the Prince of Yan, to supplement his guard corps, against Emperor Gaozu's regulations. When this was revealed to Emperor Gaozu, Emperor Gaozu rebuked Li Jiancheng and exiled his guard commander Keda Zhi (). When, subsequently, Li Jiancheng nevertheless requested the commandant at Qing Prefecture (, in modern Qingyang, Gansu), Yang Wen'gan (), to conscript troops, presumably to guard against Li Shimin, the officers Erzhu Huan () and Qiao Gongshan () informed Emperor Gaozu that Li Jiancheng was encouraging Yang to start a rebellion so that they could seize power together. Emperor Gaozu, then at Renzhi Palace (, in modern Tongchuan, Shaanxi), was incensed, and summoned Li Jiancheng, then at Chang'an, to Renzhi Palace. Li