In other words, Qin Shihuang built the Great Wall of Wan Li and stationed 300,000 troops to prevent the invasion of Xiongnu in the north. In addition, he specially sent general Zhao Tuo to lead 500,000 Qin Jun to the barbarian land (now Guiyue) and set up camp to guard the camp. In 209 BC, when Qin Ershi was in power, due to years of popular grievances, farmers in osawa Township rose up and rebelled against the rule of the Qin Dynasty, which soon spread all over the world.
At this point, the Qin Dynasty urgently transferred Zhao Tuo slate back to North Korea for support. Unfortunately, it was delayed by the wolf soldiers in Lingnan area by mountain guerrilla tactics, so that they were trapped in it and finally failed to catch up with the support. With the beginning of the anti-Qin movement, it evolved into the Chu-Han war. Knowing that the Qin Dynasty was gone, Zhao Tuo, who was far away in Lingnan area, simply occupied Lingnan area and the north of Annan, and established Nanyue State, calling Nanyue Emperor, so half of Vietnam's territory belonged to Nanyue State at that time.
Later, the Vietnamese thought that South Vietnam was an important dynasty in their history. Zhao Chao? . By the time of Emperor Wu of the Han Dynasty, South Vietnam was included in the territory of the Han Dynasty, and northern Vietnam was called Jiaotoe. In the subsequent dynasties, ethnic groups in northern Vietnam often revolted for independence. In the Song Dynasty, Song Taizong began to send troops to North Vietnam to pacify them. Unfortunately, Song Jun was defeated by the Vietnamese army in the mountainous area of Jiao Jiao, and then retreated to the Song Dynasty. Song Taizong had no choice but to give up the decision to attack North Vietnam.
After the Song Dynasty, Vietnam officially developed independently. At the beginning of the Yuan Dynasty, Yuan Taizu could not tolerate Vietnam's independence, so he sent troops to crusade, and the Yuan-Vietnam War started. At first, people thought that Mongolian iron hoofs could conquer the land of the Central Plains, not to mention the small Guo. Unexpectedly, after the Yuan army went deep into Vietnam, it was unexpectedly beaten head-on by the other side, leading to a fiasco.
After a long period of mutual consumption, Vietnam was gradually exhausted because of its small country, so it signed an armistice agreement with the Yuan Dynasty and became a vassal state of the Yuan Dynasty. During the late Yuan Dynasty and the early Ming Dynasty, Emperor Yongle was confident that he could swallow Annan in one gulp, so he sent troops to attack Vietnam. He didn't want to fight for several years without success, and all ended in failure, so that Vietnam could regain its independence.
Throughout the history of China, from the Qin Dynasty to the Ming Dynasty, these dynasties sent troops to Vietnam, but most of them failed. What is the reason? To sum up, there are three points:
The first is the terrain and environment. From the map, northern Vietnam is a tropical jungle with many mountains and trees, frequent wildlife and no roads. This is an advantage for Vietnamese who are familiar with the terrain. They can attack the enemy at night, and quickly escape into the jungle and disappear without a trace, so that soldiers in the Central Plains cannot kill them. For example, in the US-Vietnam War during the Cold War, the US military was advanced in equipment and had many advantages. But once in the jungle of northern Vietnam, there was still no way to take the Vietnamese army, and finally it was dragged into it.
Second: climatic reasons. Vietnam is a tropical climate region, especially in mountainous areas. After the Central Plains army went deep into the past, it ate and slept there day and night, which led to frequent acclimatization of soldiers due to climate problems. At that time, doctors were backward, which made minor illness become serious illness, and finally the combat capability of soldiers was greatly weakened.
Third, the threat from the north, including the past dynasties, is mainly in the north, where there are Xiongnu, Turkic and Mongolian tribes, so the Central Plains court needs to pay attention to their invasion at all times. Vietnam is located in the south, remote and desolate, and long-term operations are often difficult. Usually an army is sent there, and if it can win, it will win. If you can't fight, you will lead the troops back to the DPRK, so as not to delay for a long time and be invaded by foreigners in the north.