Off topic, back to the point, why is the change of Xuanwu Gate a premeditated coup by Emperor Taizong and Li Shimin? Let's take a look at how Li Shimin embarked on this road step by step.
In May of 6 18, Emperor Yangdi You Yang and Tang Wang Li Yuan were in the Zen position, and Li Yuan ascended the throne, so he changed his country name to Tang and martial arts to Yuan, thus creating the Tang Dynasty. After Li Yuan established the Tang Dynasty, he fought six major battles, four of which were commanded by Li Shimin, in order to eliminate the separatist forces. It can be said that Li Shimin basically laid more than half of the whole territory in the early Tang Dynasty.
After the Battle of Luoyang, Li Shimin's meritorious service was too high, which led to the closure of Tang Yuan. It is impossible to abolish Prince Li and replace him. Finally, he created a "general" position, second only to Emperor Tang Yuan and Prince Li, and above all princes and princes. In the Tang Dynasty, only Li Shimin won the post of General Ce Tian.
The most terrible thing is that the position of General Ce Tian has the right to build a house, set up a government office and form his own team. This right was originally only available to the Prince of the East Palace. If this is the case, it actually means that Tang Gaozu didn't know what was wrong in the past, and even gave Li Shimin a right that the East Palace didn't have, that is, casting money. In the fourth year of Wude, Tang Gaozu reformed coins and issued a new coin "Kaiyuan Bao Tong".
After gaining such great power, those people must have a group of people to follow. Imagine that Prince Li has his own team, and the King of Qin also has his own team. If Prince Li ascended the throne, the king of Qin would definitely be suppressed. That's for sure. Everyone in each group needs to establish their future power position from the dragon's works. People in Li Shimin, the king of Qin, must be thinking the same thing, so they will persuade Li Shimin, the king of Qin, from time to time.