,
Taipei.|437x437px Around the same time, Li Gui's official An Xinggui (安興貴) captured Li Gui in a coup and surrendered the state to Tang. Tang, however, was facing a threat on a different front, as
Liu Wuzhou made a major attack south, taking over much of modern Shanxi, which Tang had controlled, and appearing poised to further attack Tang's capital Chang'an. Around the same time, the lower
Yangtze region, which had been in a state of confusion ever since Emperor Yang's death, was coalescing around three different competing figures—the former Sui official
Shen Faxing, who declared himself the Prince of Liang and controlled much of the territory south of the Yangtze; the rebel leader
Li Zitong, who controlled Jiangdu and the surrounding regions, declaring himself the Emperor of Wu; and
Du Fuwei, who submitted to Tang and was created the Prince of Wu. In late 619, Tang forces, commanded by
Li Shimin, began a counterattack against Liu Wuzhou. By summer 620, Li Shimin had defeated Liu, who abandoned his territory and fled to Eastern Göktürk. His Dingyang state was integrated into Tang. After defeating Dingyang, Li Shimin had his sights set on Zheng. He advanced to the Zheng capital Luoyang and put it under siege. Many Zheng cities surrendered to Tang, forcing
Wang Shichong to seek aid from Dou Jiande's Xia state. Dou, reasoning that if Tang destroyed Zheng, his own Xia would be cornered, agreed, and he advanced south toward Luoyang, seeking to lift the siege. Around the same time,
Du Fuwei (now using the name Li Fuwei, having been granted the imperial surname of Li by Emperor Gaozu) defeated Li Zitong, who in turn defeated Shen, forcing him to commit suicide. Li Zitong now had Shen's former territory, while Li Zitong's former territory was held by Li Fuwei in Tang's name. In spring 621, with Dou approaching, Li Shimin advanced east to the important
Hulao Pass and held position there. When Dou engaged him, he
defeated Dou and captured him. In fear, Wang surrendered. Emperor Gaozu executed Dou while exiling Wang (although Wang was subsequently killed by the Tang general
Dugu Xiude (獨孤修德), whose father had been executed by Wang). Wang's Zheng state and Dou's Xia state were annexed by Tang, although former Xia territory soon rose under the leadership of Dou's general
Liu Heita, who declared himself the Prince of Handong, and modern
Shandong, which had been controlled by the agrarian leader
Xu Yuanlang but had successively submitted to Zheng and then to Tang, rose as well under Xu, who declared himself the Prince of Lu. Also in 621, Emperor Gaozu's nephew
Li Xiaogong the Prince of Zhao Commandery attacked
Xiao Xian's Liang state in southern China, putting the Liang capital
Jiangling under siege. Xiao, not realizing that relief forces were approaching, surrendered, and most of his state was annexed by Tang, while some of Xiao's army submitted to
Lin Shihong. Around the same time, Li Fuwei defeated Li Zitong, forcing Li Zitong's surrender, and Li Zitong's Wu state was also annexed by Tang. In spring 622, Li Shimin defeated Liu Heita, forcing Liu to flee to the Eastern Göktürks, but Liu returned later that year with Eastern Göktürk aid, reoccupying the former Xia territory. In winter 622, Li Shimin's older brother
Li Jiancheng the
Crown Prince defeated Liu again, and in spring 623, Liu, in flight, was betrayed by his official
Zhuge Dewei (諸葛德威) and executed by Li Jiancheng. Earlier, Lin Shihong had died, and his Chu state dissipated, with the cities gradually submitting to Tang, and soon after Liu's death, Xu, who had repeatedly been defeated by Tang forces, was also killed in flight. By this point, other than Liang Shidu and
Gao Kaidao in the extreme north, China was largely reunited, if somewhat nominally, under Tang rule. In fall 623, however, with Li Fuwei at Chang'an, Li Fuwei's lieutenant
Fu Gongshi rebelled at Danyang, declaring himself the Emperor of Song and controlling the territory formerly under Li Fuwei's control. By 624,
Li Xiaogong had defeated and killed Fu, reintegrating Song territory into Tang, while Gao, faced with a coup led by his subordinate Zhang Jinshu (張金樹), committed suicide, and his Yan state was also integrated into Tang. Meanwhile, Liang Shidu, protected by Eastern Göktürk aid, was holding up against Tang attacks, and Tang itself was continually harassed by Eastern Göktürk raids. After
Li Shimin ambushed and killed
Li Jiancheng and another brother,
Li Yuanji the Prince of Qi in 626 and effectively forced Emperor Gaozu to yield the throne to him (as Emperor Taizong), however, Tang began to turn the situation around. By 628, with Eastern Göktürk in internal turmoil due to disagreements between the
Jiali Khan Ashina Duobi (Ashina Duojishi's younger brother) and the subordinate Tuli Khan, Ashina Shibobi (阿史那什鉢苾, Ashina Duojishi's son), it was no longer able to protect Liang Shidu, and under Tang siege, Liang Shidu's cousin Liang Luoren (梁洛仁) killed Liang Shidu and surrendered. China was now under the rule of Emperor Taizong. == See also ==