1. The Yuan Dynasty carried out the policy of ethnic oppression, and divided ethnic groups into several grades, among which the highest grade was Manchu, the second grade was Manchu, and the lowest grade was Han. The ethnic policy of the Yuan Dynasty was very cruel. As long as there are any rebels, they will be killed at once, and the people will kill them at every turn. Mongolian troops invaded the Song Dynasty and created a no-man's land hundreds of kilometers wide in North China, all of whom were killed. This is very similar to the way the Japanese invaders later created no man's land in North China. Therefore, the development of China in Yuan Dynasty was at a standstill.

2. Early Manchu adopted a policy similar to that of Yuan Dynasty to suppress the Han nationality. There were famous "Yangzhou Ten Days" and "Jiading Three Slaughters" in history. Later, after Emperor Kangxi ascended the throne, he gradually realized the importance of ethnic issues, implemented the policy of Manchu-Chinese integration, and advocated the position of "Manchu-Mongolian-Chinese-Tibetan family". So the Qing dynasty developed better. The Yuan Dynasty only existed for more than 90 years, and the Qing Dynasty lasted for nearly 300 years.