In the ninth year of Wu De (626), the crown prince Li Jiancheng and the Qi king Li Yuanji planned to take advantage of the opportunity of the Eastern Turks to harass the border and wipe out the elite generals of Li Shimin, the king of Qin, and completely destroy Li Shimin's most important political capital. Under such a critical environment, Li Shimin was determined to launch the "Xuanwumen Revolution".
In order to ensure the success of the coup, Li Shimin ordered all his subordinates in Chang'an to rush to the Palace of Qin to set a plan and accept the task. As top strategists who had followed Li Shimin for many years, Fang Xuanling and Du Ruyi also infiltrated the Qin Palace disguised as Taoist priests and formulated a textbook-level armed coup plan.
What is strange is that at that time, the Manchu Dynasty knew that Fang Xuanling and Du Ruyi were the most important advisers of Li Shimin, the King of Qin. However, on the eve of the "Xuanwumen Revolution", Fang Xuanling and Du Ruyi once refused to go to the Qin King's Mansion, and later infiltrated the Qin King's Mansion disguised as Taoists. What's going on here?
After the Tang Dynasty unified the world, the strength of Li Shimin, the King of Qin, developed to the point where he threatened Emperor Li Yuan, not to mention the crown prince Li Jiancheng. Faced with such a formidable opponent, Li Jiancheng's response was to weaken the political power of the Qin wang clique. The first method was to win over the subordinates of the Qin Dynasty.
However, Li Jiancheng's solicitation was basically useless, and no one in the Qin Wang clique until the "Xuanwumen Revolution" turned against the water, and Li Shimin even used this to install undercover agents in the princely clique. Li Jiancheng also subsequently carried out political persecution of the qin royal subordinates, but because Li Yuan did not want to bear the charges, it still had little effect.
However, Li Jiancheng found that the official laws of the Tang Dynasty could be used. It turned out that Tang Dynasty law strictly restricted the exchange of court officials with princes, and once discovered, they were severely punished. If the subordinates of the Qin Dynasty were to serve as officials of the imperial court, their personal and political ties with Li Shimin would be severed.
Li Jiancheng recommended Fang Xuanling and Du Ruyi as insignificant mid-level officials of the imperial court, which was also in line with Li Yuan's idea of weakening Li Shimin's clique. Therefore, a few months before the "Xuanwumen Revolution", Fang Xuanling and Du Ruhan were appointed as the Ministry Ofshiro Zhong (Department Bureau Level), and thus were transferred out of the Qin Dynasty.
Because of this, Fang Xuanling and Du Ruyi could not openly enter the Qin Palace before the "XuanwuMen Change", and had to infiltrate in disguise as Taoists. In order to ensure the success of the infiltration, Li Shimin, the King of Qin, also specially sent Changsun Wuji and Wei Chi Jingde to protect him.