Li Chengqian
By 643, Li Chengqian was so fearful that Emperor Taizong was about to depose him that he conspired with a number of officials, including the major general Hou Junji, Emperor Taizong's brother Li Yuanchang (李元昌) the Prince of Han, the imperial guard commander Li Anyan (李安儼), his cousin Zhao Jie (趙節), and Du Chuke's nephew Du He (杜荷, Du Ruhui's son), to overthrow Emperor Taizong. That summer, however, Li You (李祐) the Prince of Qi, a younger brother to both Li Chengqian and Li Tai, resentful of the head of his household, Quan Wanji (權萬紀), killed Quan and then rebelled. Li You was soon defeated and captured, and when Emperor Taizong investigated Li You's co-conspirators, Li Chengqian's associate Gegan Chengji (紇干承基), who had been an assassin for Li Chengqian and was involved in his conspiracy, was arrested and sentenced to death. Gegan, in order to save himself, revealed the plot. Emperor Taizong, in shock, convened the senior officials Zhangsun Wuji (Empress Zhangsun's brother), Fang Xuanling, Xiao Yu, and Li Shiji, as well as officials from the supreme court, the legislative bureau, and the examination bureau, to investigate, and the extent of the plot was revealed. When Emperor Taizong requested opinions on what to do with Li Chengqian, Lai Ji suggested sparing him, and Emperor Taizong agreed. He deposed Li Chengqian and reduced him to commoner rank, while ordering Li Yuanchang to commit suicide. Hou and the other conspirators were all executed.