In the sixth year of Yonghui (655), Emperor Gaozong of Tang won the final victory of "deposing Wang Liwu" and basically overthrowing the Changsun Wuji clique, which controlled the government. In the process of "deposing Wang Liwu", Li Ji's support played a decisive role, directly causing Tang Gaozong and his eldest son Wujie to turn their faces. So after getting the support of Li Ji, why was Tang Gaozong able to make up his mind to turn his face with the eldest grandson?
Emperor Gaozong of Tang faced a situation that made him very unhappy in the early days of his ascension to the throne, and the eldest son Wuji's party completely maintained the government. However, many officials in the imperial court at that time did not support Changsun Wujie, but they also did not trust Tang Gaozong's strength and did not dare to openly support the emperor. Therefore, Emperor Gaozong of Tang needed to do one or two major things that disobeyed his eldest son and gather these potential officials under his command.
After several attempts and deliberations, Emperor Gaozong of Tang finally decided to take the "abolition of Wang Liwu" as a breakthrough. However, according to the political system of the Tang Dynasty, the replacement of the empress had to go through the procedure of "three provinces", and the chief officers (prime ministers) of the "three provinces" were all people with no scruples. Therefore, Emperor Gaozong of Tang hoped to persuade his eldest son Wuji to agree to change the empress in the early stage of "deposing Wang Liwu", but it had no effect.
Since the persuasion was ineffective, Tang Gaozong could only directly replace the eldest son Wujie's henchmen who controlled the "three provinces", that is, to openly turn his face with the eldest grandson Wujie. However, Emperor Gaozong of Tang had two concerns about publicly turning his face to Changsun Wujie: First, Tang Gaozong's foundation in the dynasty was very shallow, and there was no suitable candidate to take over as the governor of the "Three Provinces"; second, Changsun Wujie's political energy was too great, what if he launched a palace coup?
It was precisely because of the two concerns that Tang Gaozong did not turn his face to the eldest grandson for a long time. At this time, two changes that were very beneficial to Tang Gaozong appeared in the "abolition of Wang Liwu": first, a group of middle-level officials represented by Xu Jingzong and Li Yifu stood up and openly supported Tang Gaozong, so that Tang Gaozong had a real person in the dynasty; second, Sikong and the British duke Li Ji explicitly supported Tang Gaozong.
Li Ji was the first military leader of the Tang Dynasty at that time. Li Ji's support meant that Emperor Gaozong of Tang had the support of the Tang military, so there was no need to worry about the eldest son Wujie launching a coup d'état. Because of this, Emperor Gaozong of Tang immediately deposed Chu Suiliang, the second-ranking figure in the Changsun Wuji Party, after Li Ji's statement, and replaced or vacated all the governors of the "three provinces", and the "abolition of Wang Liwu" was also successful.