[Why] After the founding of Tang, Prince of Qin Li Shimin's military exploits were brilliant and his prestige was high, deeply unsettling Crown Prince Li Jiancheng and Prince Qi Li Yuanji. The two camps launched a brutal imperial succession contest at court. [What] Li Shimin, persuaded by his subordinates, struck first by laying an ambush at Xuanwu Gate in Chang'an. He personally shot Crown Prince Li Jiancheng dead, his retainers killed Prince Qi, and he forced his father Li Yuan to abdicate as Retired Emperor. [Who] Li Shimin was a Prince of Qin with extraordinary military insight and iron-blooded means, who became the timeless wise sovereign Taizong after seizing power. Li Jiancheng was careless in his guard and was killed in the power struggle. [How] This bloody coup secured Li Shimin's legitimate succession to the throne and avoided the empire's slide into another civil war fragmentation. It became the most cruel and bloody classic of imperial succession in the Huaxia historical record.
Why
The historic event of Xuanwu Gate Incident represents a key developmental peak of the Huaxia dynastic system. The most famous and bloody palace coup in Chinese imperial history. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.