What's the unknown secret behind Li Shimin's "Change of Xuanwu Gate"?

Li Shimin and the Change of Xuanwumen: Li Shimin, a great monarch in the history of China, initiated the rule of chastity which was praised by later generations. However, Li Shimin's throne was improperly obtained. After the change of Xuanwumen, Li Shimin killed Prince Li and Li Yuanji, urged Tang gaozu to decentralize, and finally achieved his generation.

After Li Yuan proclaimed himself emperor, he attached great importance to courtiers, doubted meritorious deeds, and was fond of debauchery, which made him unable to make greater achievements after he became emperor. Pei Ji, former deputy supervisor of Sui Dynasty, was a fair-weather friend of Li Yuan when he was in Jinyang. He sent maids to Tang Gaozu privately and often gambled and drank with Tang Gaozu day and night. When Jinyang Uprising, Pei Ji sent another 500 maids to March with him in Tang Gaozu. After Li Yuan proclaimed himself emperor, he thought that Pei Ji had made the greatest contribution, and made him a high-ranking official and a confidant.

Liu Wenjing, the former envoy of Jinyang, together with Li Shimin, instigated the army to fight in the south and north, and was the founding hero of the Tang Dynasty. Liu Wenjing was very upset that he was under Pei Ji, so he had a conflict with Pei Ji. One day in 6 19 AD, Liu Wenjing complained after drinking, and Pei Ji took the opportunity to frame him, saying that Liu Wenjing wanted to oppose the imperial court, but Li Yuan listened to him and killed Liu Wenjing. Tang Gaozu's unclear rewards and punishments have deepened the contradictions and struggles among officials.

In the later period of Tang Gaozu's rule, he accepted concubines and enjoyed himself in the harem. When some concubines provoked relations with each other, they failed to stop them as early as possible. Instead, I listened to rumors, which led to brothers and soldiers meeting each other and bleeding. With the smooth progress of the United War, Li Yuan's thoughts began to relax, content with pleasure, and no longer cared about political affairs, which directly led to the problems of the Crown Prince.

Tang Gaozu wanted his sons to live in harmony, but he didn't have a clear idea about establishing a crown prince, which led to an argument between the two brothers. When Liu Wuzhou invaded Taiyuan and threatened Chang 'an, Tang Gaozu personally saw off his son Li Shimin and promised to make him a prince when he returned victorious. But when he came back, he broke his word and listened to his concubines' intercession, thus keeping the position of the prince. This directly led to the discord between brothers and became the fuse of fierce disputes between princes.

Prince Li and the King of Qin waged a life-and-death struggle for the throne. In the summer of 626 A.D., when the Turks invaded China, Li Xiang recommended Li Yuanji, the king of Qi, as the marshal of the expedition, hoping to take this opportunity to take the elite soldiers of the court of the State of Qin as his own and get rid of the king of Qin. Unexpectedly, this plot was learned by Li Shimin. At this critical juncture, Li Shimin preemptively told the Prince and the King of Qi about the harem fornication, and Tang Gaozu decided to question him the next day. The next day, Li Shimin set an ambush at Xuanwu Gate. When the prince and the King of Qi passed through the Xuanwu Gate, Li Shimin and his men killed them, and told his heart Wei Chijingde to report to Tang Gaozu in armor.

At this point, Tang Gaozu was sitting on a little dragon boat with his ministers Xiao Yuqing and Pei Ji, rippling in the pool. He was horrified to see Wei Chijingde standing on the shore armed to the teeth. Wei Chijingde said that the prince and the king of Qi rebelled, and the king of Qin had put them to death and sent me to protect them. Tang Gaozu was dumbfounded after hearing this. Xiao Yu, who is next to her, urged to entrust the state affairs to the king of Qin, and also urged to write a letter to the king of Qin, so as to quell the riots in the East Palace and the King of Qi. Tang Gaozu was forced to write a letter, ordering all the troops to obey the disposal of the King of Qin and making Shimin a prince. At this time, the situation in the whole country was basically controlled by Li Shimin, and Li Yuan was helpless and expressed his willingness to abdicate early.