Therefore, the Sui Dynasty perished.
Therefore, the Tang Dynasty lost a generation of Emperor Taizong.
The Yuan Dynasty really succeeded, and it also established Korea Province, made the king of Korea the governor, and married the princess to the king of Korea. ...
But Koreans cherish their independence very much and are unwilling to "ruin a quarrel" with China. Seeing that the regular war could not defeat China, they tricked the Yuan Dynasty into fighting Japan and chose between the two sides. Then the Yuan Dynasty became stupid and went to fight. As a result, hundreds of thousands of troops sank to the bottom of the sea forever ...
In this way, by the time of the Ming Dynasty, the Ming Dynasty simply gave up its intention of actually controlling the Korean Peninsula and only asked them to be "loyal friends". In addition, the place in North Korea that belonged to the official version of the Yuan Dynasty was ceded to North Korea in vain.
It was because of this cession that Jurchen Aisingiorro, who had originally settled in the northern part of the Korean peninsula but refused to be a slave of the Koreans, returned to China.
Aisingiorro later established Houjin, later renamed Qing. At the beginning of the People's Republic of China, before he entered the Central Plains, he conquered Korea twice and forced it to submit, but he did not advocate the establishment of de facto rule on the Korean Peninsula.
After the establishment of the Qing dynasty, the control over North Korea was more relaxed, and only a loyal vassal state was required.