Why did the Ming Dynasty withdraw its troops from Annan and regain power?

Vietnam has a long and narrow terrain, and the west is full of mountains-the Changshan Mountains in Laos. During the Ming Dynasty, although the Ming army occupied Vietnam, after the Vietnamese attacked us, they could quickly escape into the western mountainous areas. The tropical rain forest and mountainous terrain in the west also limit the mobility of our army. Therefore, the tax revenue of the Ming army in Vietnam in the Ming Dynasty was 72,000 yuan, while the military expenditure was 3 million yuan. If you can't make ends meet for a long time, you can't explain.

2. Climate

Because Viet Nam is in the tropical rain forest, China immigrants have a bad life. In fact, during the Vietnam War, the Vietnamese army was still uncomfortable in the rainforest. A large number of soldiers suffering from malaria turned to China for help, which contributed to the research and development of artemisinin and won the Nobel Prize. The aborigines in Vietnam can live on wild fruits, and this climate and terrain are not conducive to the combat effectiveness of farming people.

3. Population pressure

In the historical dynasties before the Qing Dynasty, the population of China was 80 million, not exceeding 654.38+0.5 billion. There is enough land in the middle and lower reaches of the Yellow River and the Yangtze River. When the population increased by 400 million in the late Qing Dynasty (due to the high yield of crops), the areas originally defined as strategic buffer zones (Northeast, Northwest, Indo-China Peninsula and Taiwan Province Province) had to be turned into core residential areas.

It is in this context that it is imperative to recover Xinjiang, transform the southwest and open up the northeast. Northeast China is a typical case. But the fundamental reason for the success of reclamation in southwest China is that there are enough people infiltrating.

4. During the Tang and Song Dynasties, Yunnan was still an independent country-Nanzhao and Dali. China really digested Yunnan in the Ming and Qing Dynasties (Taiwan Province Province was actually occupied by the Qing Dynasty), and it took longer to go south. Obviously, because of the western colonists, there is no such time. So our country ends in Yunnan and Guangxi.