Li Shimin killed his two brothers at the Xuanwu Gate, executed their ten sons and had the throne from his father within two months

Li Yuan founded the Tang dynasty in 618 as Emperor Gaozu. His eldest son, Li Jiancheng, was crown prince. His second son, Li Shimin, Prince of Qin, had led the main campaigns. The Zizhi Tongjian records that Shimin accused his brothers to their father of misconduct with palace women, and Gaozu summoned all three for questioning the next morning. On 2 July 626 Shimin hid troops at the Xuanwu Gate, the north gate of the palace. Jiancheng and their brother Li Yuanji, Prince of Qi, sensed danger near the Linhu Hall and turned their horses. Yuanji drew his bow three times and could not pull it; Shimin shot Jiancheng dead, and Yuchi Jingde killed Yuanji. About 2,000 of the dead princes' guards attacked the gate and were held off. Jiancheng's five sons and Yuanji's five sons were executed and struck from the imperial clan register. Shimin's commanders wanted to kill more than 100 of the brothers' followers and seize their families; Yuchi Jingde argued against it, and they were spared. In the eighth month Gaozu issued an edict passing the throne, and Shimin took it as Emperor Taizong. In 643 Taizong's own crown prince, Li Chengqian, was accused of plotting a coup, found guilty and deposed.