That's a good question First of all, Vietnam was completely independent from China in history, and it was in the Ming Dynasty. At least in the Ming Dynasty, Vietnam was once again briefly ruled by the Central Empire, which was called Annan Ming Dynasty (1407–1427), that is, the three dynasties of Yongle, Hongxi and Xuande lasted for 20 years. However, the rule of the Ming Dynasty aroused the resentment and resistance of Vietnamese aborigines, among which Li Li, a blue mountain aristocrat, had the greatest influence, and ended the Ming Dynasty after ten years of anti-Ming war (14 18-1427). Since then, Viet Nam has never been ruled by China. There is a term in Vietnam called the Northern Shu Period.

Speaking of Yunnan, it was not until the late Qing Dynasty, that is, the Xianfeng period, that Yunnan was barely controlled. Before Xianfeng in Qing Dynasty, the central government could not effectively control northern Yunnan. The local productivity level can't support the army that controls the whole area.

Yunnan and Vietnam are only nominally independent, but in essence they have always been independent. Wu Sangui and Shangkexi are divided into Yunnan and Guangxi, and you will know what it means.

In this place of Yunnan, in the Kangxi era, it was difficult for Wu Sangui to spare enough strength to confront the central authorities, and the central authorities were unable to control such a place, so they sent people like Wu Sangui and Shangkexi.

The economic development of coastal areas cannot rely solely on waterways. There must be a high degree of medical development. As long as people gather together, various diseases and plagues will naturally appear. In the era of underdeveloped medicine, it is less likely that plague will break out in the north because of the cold weather in winter. The south is different. As long as the population gathers to a certain amount, a plague will inevitably break out.

When the Ming Dynasty was established, the local power shogunate in Yunnan was destroyed, and the broken chieftain began to return to China. With the efforts of the Ming and Qing dynasties, most of the toast in Yunnan and Guizhou and even in northern Myanmar bathed in the favor of the emperor and began to study classics. Become the same county as the headquarters of China, and become a part of the headquarters of China.

The Yuan Dynasty failed to conquer Vietnam, and Vietnam also had an integrated regime, which was similar to that of a vassal state in our time. In the Ming Dynasty, Vietnam recovered what it had lost and recovered what it had lost. Without external intervention, they will gradually return to their homeland, bathe in the emperor's grace, learn enlightenment and start reading Confucian classics. However, in modern times, the rapid development of naval vessels opened the door to China. 1885 After the Sino-French War, Vietnam became a European colony from a separatist region. Catch up with the wave of building a nation-state, and then embark on the road of independence.