Li Yuanji
Early 626, the Tujue attacked the frontier of the Tang empire. At Li Jiancheng's recommendation, Li Yuanji was commissioned for a military campaign against these hostile forces, thus Li Shimin's best generals and crack troops were transferred to Li Yuanji. Thereafter, Li Shimin received word from his men that Li Jiancheng and Li Yuanji had taken preparations to assassinate him when he would see off Li Yuanji as was the custom during the onset of a military campaign.