In the early morning of July 2, 626, a tragedy happened outside Xuanwu Gate of Li Tang Palace, which was just nine years old. The whole incident involved hundreds of lives and even shook the rule of the Tang Dynasty in Hebei. This is the famous "Xuanwumen Change" in the history of China. As the winner of this coup, Li Shimin, Emperor Taizong, made many moves in the history books, so the truth of the incident has been confusing and there are different opinions. It can be said that "a thousand people have a thousand' changes in Xuanwu Gate'".

The change of Xuanwu Gate had a far-reaching influence in the history of the Tang Dynasty, which set a precedent for the successors of the Tang Dynasty to seize power through an armed coup. However, due to the tampering of Li Shimin, the winner, the record of this matter in history books is vague and full of doubts. Now I will sort out the relevant historical materials in order to restore the truth of history.

The record of the change of Xuanwu Gate in the official history is as follows: Li Tang was founded because of Li Shimin, the king of Qin, and Li Yuan's army in Jinyang was "coerced" and "guided" by Li Shimin, but he didn't make much contribution to starting a business; Li indulged in debauchery, although he did not make great achievements, but he was able to board the East Palace as the eldest son. Therefore, Tang Gaozu repeatedly said that he would replace Li Shimin with a prince, but Li Shimin resolutely refused, and the matter was temporarily forgotten. Like Prince Li, Li Yuanji, the king of Qi, was not meritorious, cruel and ambitious, so neither of them was liked. Li was worried that he would try to seize his crown prince, so he formed an alliance with Yuanji to confront him on the condition that he would be the emperor's brother in the future.