First, it is not easy to defend the south, and it is even harder to attack the north.
Geographically, Jinling City is indeed a good place, with the natural barrier of the Yangtze River in the north and the rich Jiangnan in the south. It can also be called the land of Long Mai in geomantic omen. But it is far from the traditional imperial capitals of Luoyang and Chang 'an. There are many hills and passes to the east of Luoyang, and mountains to the north and south. Hulao Pass and Xuanyuanguan are both important military cities. In case of danger, Hangu and Tongguan can retreat to West Chang 'an. To the east of Chang 'an, there are Luoyang and the Pass, and you can retreat to Bashu in the south. Both of them echo each other, can attack and retreat, and have incomparable advantages in arranging troops and deploying resources. Therefore, it has been known as East and West Beijing since ancient times. However, there is only one Yangtze River guarding the north of Nanjing. Although the Yangtze River is called a natural barrier, it is very easy for the northern army to reach the river from the East China Plain all the way south. The river in Nanjing is very wide, and it is very sad. But there are many ferries in the upper reaches, and the front line is long. If it is breached, we can attack Nanjing from the west. These six short-lived dynasties, except Jiangsu and Zhejiang, were not fully developed in other places in the south of the Yangtze River, with the sea in the southeast and the vulnerable places in the west. Therefore, if Nanjing falls, the country will perish in World War I. ..
Second, rich products are a hotbed of inertia.
This is the earliest place where Jiangnan was developed, and it is precisely because of the superior natural conditions that the land of fish and rice was formed early. The rulers of the Six Dynasties were here, the emperor expanded the capital, and courtiers set up businesses. The climate is humid, the scenery is beautiful, the products are rich and the economy is prosperous. As such a livable place, life is comfortable. How did you make them have the idea of rekindling the war and returning to the north? As a group of rulers who lost in the north and moved to the south, they enjoyed the splendor and the decadent voice of the listeners, and the officials were intoxicated with it, and the atmosphere became more and more intense. Think of the original escape, today's day can be described as family happiness.
Third, the most serious thing is that the rulers' political system is backward and their comprehensive strength is declining.
In these six dynasties, except for the pioneering capital Wu, all other regimes were rotten. After the demise of the Western Jin Dynasty, the Jin people built health across the capital, the gentry was rampant, and the literati were intoxicated. The imperial court has never been able to organize a decent northern expedition. The ruling class fought among themselves, contending for power and profit, monopolizing the general's power, and the minister killed the king. The gentry defended their own interests, while the people were in dire straits. But they never found a way to stabilize and revitalize the country. So the emperor took turns to do it, and whose house to go to tomorrow. After the temporary unification of the Western Jin Dynasty, the Southern Dynasty, which had been separated from the North since the end of the Eastern Han Dynasty, became a joke in history.
During the Six Dynasties, China's economic center of gravity was still in the north. Even if Jiangsu and Zhejiang, a land of plenty, are developed, half of the country's comprehensive strength can't compare with the north. Economy and taxation are at a disadvantage, population is at a disadvantage, and strategic materials such as war horses are in short supply. Coupled with the lack of courageous rulers, it is a blessing for the north to get rid of more than a hundred years of war. Sui Wendi Sui Wendi ended the Northern Rebellion, Jinling won the first battle in Kunming, the world was unified, and China ushered in the prosperous dynasty era.
Even the later Ming Empire and the Republic of China did not make Nanjing their capital for many years, so that people in later generations contacted history and summed up the concept of a short-lived dynasty with Nanjing as its capital. In fact, in the final analysis, the biggest reason lies in the thoughts of the rulers. Judy, the founding emperor of the Ming Dynasty, moved to Beijing because he was prepared for danger in times of peace and set an example. Wang Daming Cai Chao's national strength is growing. There is no necessary connection between Long Mai and Nanjing.