The change of Xuanwumen was a bloody coup at the North Palace Gate of the Inner Palace by General Ce Tian and Li Shimin, the second son of Tang Gaozu's second son Li Yuan, on the fourth day of June (July 2, AD 626) in Wude, the capital of Chang 'an (now Xi 'an City, Shaanxi Province) in the Tang Dynasty.

After Tang Gaozu acceded to the throne, Li Jian was the prince, Li Shimin was the king of Qin, and Li Yuanji was the king of Qi. Of these three people, Li Shimin contributed the most. Jinyang arise, is his idea; In the next few battles, he also made the greatest achievements. Li Gonggong was inferior, and only because he was the eldest son of Gaozu did he get the position of Prince.

The historical reasons for the change of Xuanwu gate may be: the contradiction between Li and Li, Li's dissatisfaction, his ambition and so on.

1, the contradiction between Li and

Tang gaozu's two sons competed for the throne. Li, his eldest son, was once made a prince, but his talent and prestige were inferior. Tang Gaozu's second son, Li Shimin, has made outstanding achievements in military service and won the support of soldiers and generals.

2. Li is very dissatisfied with.

Li is dissatisfied with Li Yuan's ruling style and unfair treatment to himself. He thought that as a prince, he should have more power and status, but Li Yuan preferred Li Shimin.

3. Li Shimin's ambition

Li Shimin longed to be the emperor of the Tang Dynasty. He actively sought the support of generals and soldiers and made alliances with some nobles and officials. He used Li Yuan's unfair treatment of Li to strengthen his position and influence.

The main achievements of Emperor Taizong and Li Shimin:

1, The Rule of Zhenguan: Li Shimin has implemented a series of political, economic and military reforms, which is called the Rule of Zhenguan. He implemented an effective system of selecting officials, paying attention to selecting talents and attaching importance to the integrity of officials. He also strengthened centralization and established a perfect administrative system, which made the government more efficient and stable.

2. Territorial expansion: Li Shimin successfully expanded the territory of the Tang Dynasty through a series of wars and diplomatic means, and extended the territory of the Tang Dynasty to Liaodong, the Western Regions and Southwest China, making the Tang Dynasty one of the largest empires in the world at that time.

3. Economic prosperity: Li Shimin has adopted a series of economic policies to promote domestic economic prosperity. He implemented the system of land equalization, which reduced the burden on farmers and improved agricultural productivity. He also encouraged the development of commerce and handicrafts, strengthened foreign trade, and made the economy of the Tang Dynasty develop rapidly.