The monarch's "abandoning the long and setting up the young" is easy to cause trouble. What were the successful cases in ancient times and how did they do it?

I think there are two successful cases. One is Li Shimin, who abolished the Prince of Li Chenggan and made Li Zhi the Prince. The other is Liu Xiu, who abolished Liu Jiang and made Liu Zhuang the Prince. As for the reasons for its success, I think Li Shimin succeeded in abandoning the old and establishing the new because it was just. The reason for Liu Xiu's success is that his sons are very sensible and get along well, and the friendship between father and son has not been hurt by the position of the emperor.

Let's talk about Li Shimin first. Although he is regarded as a wise king, he still has some problems in educating his children. For example, he was too ambitious for his eldest son, Li Chenggan, and in the end, he was a little too backward. In addition, his beloved wife, Grandson Queen, died, and Li Chenggan was disabled due to illness.

The reason why Li Shimin abolished Li Chenggan is actually related to Li Chenggan's increasingly disappointing performance. He was jealous of Li Shimin's doting on his younger brother Lee Tae, but later he openly mentioned Toy Boy, wanted to assassinate his teacher, and even finally wanted to mobilize troops to rebel. Li Shimin abolished him, because he was too bastard to be the king of a country, so he had every reason to abolish him. And the reason for Li to be a prince is also very good, because Li Zhi is kind-hearted and will be a benevolent gentleman in the future.

Liu Xiuqi's success is attributed to his eldest son, Liu Jiang, who has special self-knowledge and voluntarily resigned from the position of Prince. Liu Zhuang, the son of Liu Xiuli and Yin Lihua, was the Prince, and nothing happened here. Whether Liu Xiu, Liu Jiang and Liu Zhuang, or Yin Lihua, the relationship between them is particularly harmonious. So Liu Xiu still has a group of sensible and generous children, which is why she is so successful.