The reason is simple: the geography of China determines it. The geographical trend of China is high in the north and low in the south. In order to prevent foreign invasion, the Great Wall of Wan Li was built in the north according to the dangerous terrain. But once the Great Wall defense line is broken, the enemy can go to Ma Pingchuan and drink horses to the Yellow River. The only natural barrier is the Yangtze River defense line. China originated from the Yellow River. Therefore, the Central Plains refers to the north bank of the Yangtze River. In this way, the Central Plains has become the focus of competing, competing and competing. Therefore, the war in the Central Plains caused people in the Yellow River Basin to have more sense of hardship.
Look at the Yangtze River basin again, because it is far from the Central Plains and there is a Yangtze River Graben as a barrier. In addition, the Yangtze River basin belongs to the land of plenty. Sichuan is isolated from Jiange, and the land of abundance is naturally far from war. As Li Yu said, "How many times have you known each other?" People in the Yangtze River valley will be safe and sound. Therefore, once the northern soldiers point to the south, there is only one sentence: "Once they are listed as ministers, they will shed tears for Gong E."
What about north of the Great Wall? Grassland and desert are even more difficult. So we must invade and plunder to survive. In the Central Plains, only Qiang Bing, a rich country, can sweep Mobei and point to Qilian Mountain. Therefore, the Zhou, Qin, Han and Tang Dynasties used foreign troops many times. In particular, Qin Shihuang, Emperor Wu of the Han Dynasty and Emperor Taizong fought decisive battles with ethnic minority regimes again and again. The Ming Dynasty even took Beijing as its capital (Youzhou, a border town in the Tang Dynasty) and let the emperor stay at home. The son of heaven died for his country. Ningyuan, Jinzhou and Shanhaiguan were established in the late Ming Dynasty to resist foreign aggression on a steep basis.
In Song Dynasty, Shi Jingtang ceded sixteen states to Youyun of Five Dynasties and Ten States, which led to the invasion of Liao State.
Geographically, the natural barrier is not impregnable, only the human heart is the real Jincheng Tang Chi. In the Song Dynasty, if the emperor and the imperial court were not corrupt and incompetent, they could still sweep the desert and recover the sixteen states of Youyun. There is no shame of Jingkang later. What about Guan Ningjin in the Ming Dynasty? Can't stop the Qing Dynasty from entering the Central Plains.
Being born in sorrow and dying in happiness is the key to success.