In June of the ninth year of Wu De (626), Li Shimin ambushed Xuanwumen and attacked and killed his eldest brother Li Jiancheng, the eldest son, and Li Yuanji, the third brother of the Prince of Qi, and completely resolved the dispute between him and Li Jiancheng for many years as crown princes through the way of blood at the palace gate. History refers to this incident of brotherhood and fratricide as the "Change of Xuanwu Gate".
The Xuanwumen incident is both accidental and inevitable, Li Jiancheng knows that there will inevitably be a final showdown between himself and Li Shimin, why does he take precautions? How did Li Shimin know that Li Jiancheng and Li Yuanji's brothers would enter the palace from Xuanwu Gate to see Li Yuan?
The key to understanding this problem is XuanwuMen. Xuanwu Gate is the north gate of the Chang'an Imperial Palace in the Tang Dynasty. In the early Tang Dynasty, the Chang'an Palace City Camp was built during the second year of the Sui Kai Emperor and included the Taiji Palace (Sui daxing palace), the Eastern Palace and the Yeting Palace. Taiji Palace is the largest in the middle of Miyagi Castle, and the main hall Taiji Hall is the political center of the early Tang Dynasty. There are five gates on the south side of Miyagi Castle, the Chengtian Gate in the middle and three gates on the north side, and the Xuanwu Gate is the main gate, located slightly westerly in the middle of the north wall of Miyagi Castle. Miyagi was the place where emperors and imperial families lived and handled imperial government, and was the center of Tang dynasty rule. Among them, the south side of taiji palace is the imperial city, and the east and west sides have the east palace and the yeting palace, which are relatively safe, but the north side is connected with the wilderness, and the terrain is low.
Therefore, the Xuanwu Gate on the north side of the Taiji Palace is extremely important. If the Xuanwu Gate is lost, the Taiji Palace will be in danger.
The guards of xuanwu gate were related to the safety of Miyagi and the emperor, so there were heavy guards stationed. Beginning in Sui Yang, there were strict rules for the opening and closing of palace doors. In addition to the important occasions of "Yuan Zheng and Chen Le setting up banquets on the winter solstice, pardoning sins, and removing the old cloth and the new", every month the Shuo Emperor ascended to the Taiji Hall to come to the dynasty, and when the emperor worshipped the outskirts of heaven, he entered and exited from the Chengtian Gate, and usually the gate was closed.
The emperor's daily reception of ministers and foreign envoys was held in the Two Ceremonies Hall behind the Taiji Hall. When the courtiers entered the palace, they went to the Xuanwu Gate in the north. Xuanwumen has such a close relationship with the political life of the ruling center, its importance is self-evident. The brothers Li Jiancheng and Li Shimin were incessantly accused each other, much to Li Yuan's infuriation, and he was forced to state that he would let the brothers confront each other the next day to make a final judgment. When confronted, some things of Li Shimin will naturally be exposed, taking a step back is a cliff, letting go or suddenly being cheerful, Li Shimin has to start first to be strong in order to get away with it.
For safety reasons, the gates of the Sui and Tang Palaces are very strong and heavy, and the doors are opened and closed with strict rules and regulations. Opening and entering and exiting the Chengtian Gate at will requires the emperor's hand, even the crown prince Li Jiancheng is no exception. For dereliction of duty, soldiers will be severely punished or even killed for it. The troops set up at the north gate of Miyagi Castle are collectively called the Northern Army, and the general who is responsible for the security of the Xuanwu Gate is called the General of the Left and Right Tun Camps.
If the guarding generals of Xuanwu Gate were bribed by people with ulterior motives, it would easily lead to a mutiny and endanger the emperor's safety. Li Yuan naturally understood this truth, so during the nine years of WuDe, the generals in charge of guarding xuanwu gate were Chang He and Jing Junhong, who were deeply trusted by Li Yuan.
But Li Yuan did not expect in his dreams that they had been secretly bribed by Li Shimin, just waiting for the key moment to open the door for Li Shimin. Li Shimin sneaked in from Xuanwu Gate and quietly waited for Li Jiancheng and Li Yuanji to arrive.
Li Jiancheng did not expect to be shut down and beaten at all, and the two brothers died instantly. The guards of the Eastern Palace and the soldiers of the Qi Palace heard of the change, and clamored to attack XuanwuMen, seeing that the situation was critical, Jing Junhong stepped forward and led his troops to resist and died in the rebellion. Jing Junhong's death bought Li Shimin precious time, seeing that the Xuanwu Gate was about to fall, Wei Chigong rushed to the scene with Li Jiancheng and Li Yuanji's head flying horse, and the Eastern Palace generals saw this before they scattered.
After the Xuanwumen incident, Li Shimin paid special attention to the guards of Xuanwumen and entrusted the heavy responsibility of guarding Xuanwumen to his cronies. According to historical records, in July of the ninth year of Wu De, after Li Shimin became crown prince, The eldest son Anye was made the general of the Right Guard Gate, and Li Keshi was the general of the left and right. Changsun Anye was empress dowager's half-brother, and Li Keshi was Li Jing's younger brother. In the early years of Zhenguan, when Li Shimin ascended to the throne, the person in charge of Xuanwumen security was changed to Gongsun Dawu, a confidant who had participated in the Xuanwumen Incident.