Why did Qianlong win in the north but not in the south?

The reason why Qianlong could not defeat the south. Because in terms of military strength, firearms were very powerful at that time. Because the Qing Dynasty was closed to the outside world, it had no idea that there were such powerful weapons. And the weapons used here were weapons provided by Western powers such as Britain and France after the industrial revolution. Most of them were purchased. Yes, there were also a small amount of gifts, but the Qing Dynasty basically relied on the cavalry of the Eight Banners. From the Forbidden City to the Yunnan border, the logistics and supplies could not keep up. The soldiers were not accustomed to the climate, most of them were infected with diseases, and it took several years. The war-weariness was extremely serious.