Geographically, the northern regime occupies the central plains, while the southern regime occupies the southern part of the jiangsu province, and the north occupies a great geographical advantage. Since the ancient civil war, one focus of contention has been Xiangyang, for example, the reason why the Yuan Dynasty destroyed the Song Dynasty for decades was because Xiangyang could not be defeated for a long time; another focus of contention was Jianghuai, the so-called "guarding the river must defend Huai".
In the north, there are mostly plains and horses and rivers, and people can quickly pass on government decrees to the localities through horse-drawn carriages, while in the south, because of the many hills and dense rivers, many people rely on small boats to deliver letters. In the large-scale army assembly, the North also has more advantages than the South, so the North is faster and easier to mobilize troops and assemble materials than the South.
The Yellow River Basin is the birthplace of Chinese civilization, the northern history has long been the economic center of China, the North China Plain and the Guanzhong Plain are very rich, the population is large, and the grain production is abundant. So before the Song Dynasty, the north had an economic advantage over the south. With the continuous wars and invasions of the north in history, the Han people continued to cross south, starting from the Song Dynasty, Jiangnan was continuously developed, and the economy has come to the fore.
The Western Jin Dynasty was determined by the Northern Jin Dynasty to move south to Jiankang (present-day Nanjing), the capital of the Anshi Rebellion in Jinling (present-day Nanjing) to establish the Southern Tang Dynasty, and the southern Song Dynasty at the end of the Northern Song Dynasty and the early years of the Southern Song Dynasty. Because of the limitations of the ancient political system, in addition to some founding emperors who have enterprising spirit, generally the second generation of the third generation of emperors is not as aggressive as the first generation, they will be more intoxicated with other things, and the developed economic conditions in the south are their hotbeds. Therefore, the economic superiority of the South was not used in a useful place, but was squandered on the life of the upper rulers, and the superior and comfortable life of the South constantly stimulated the determination of the Northern regime to take the South.
