The advantage of choosing Nanjing as the capital is that after the end of the Eastern Han Dynasty, especially during the Southern and Northern Dynasties, it became increasingly difficult to move the economic center. Nanjing is close to grain-producing areas, with convenient grain transportation and developed waterways. From an economic point of view, it is more cost-effective than any other city in the north. Therefore, as the capital city, Nanjing is always very prosperous, with cars and horses flowing like dragons. But why doesn’t it last long? Because the city of Nanjing is far behind from the perspective of national defense. There are Tongguan in the east of Chang'an, Dashanguan in the west, Wuguan in the south, and Xiaoguan in the north. The four passes control the passage in and out of Chang'an. They are easy to defend but difficult to attack. If not, you can escape to Shu. Luoyang borders the Yellow River to the north and Luoshui to the east, and is surrounded by eight passes including Taigu, Guangcheng, Yique, Fuyuan, Xuanmen and Mengjin. It can also be regarded as a place of physical beauty. Of course, the biggest advantage of Luoyang is that it is in the center of China, not too far from anywhere. Beijing is guarded by the Liaodong Peninsula and the Shandong Peninsula, guarding the northeast, and the emperor guards the country, which is conducive to dealing with threats from the northern grasslands. Although the Yellow River that Kaifeng relies on cannot be effective during dry periods and freezing periods, it can still run south if the situation is bad. (Northern Song Dynasty, Southern Song Dynasty) But what if Nanjing is chosen as the capital? Once the natural barrier of the Yangtze River is breached, where will it go? Wuhan? Guangzhou? That would not only make it peaceful, but directly reduce it to a small local country.
Except the Yuan Dynasty, the main threat to each dynasty came from the north. If we build a capital in the south, our strategic depth will be reduced by half! If you have no choice but to build the capital in the south, Nanjing is already the best choice.
The only national governments that chose their capitals in the south were the Ming Dynasty and the Republic of China during the Kuomintang period. When the Ming Dynasty was founded 50 years ago, Zhu Di made the painful decision to move the capital. The source of Chiang Kai-shek's power lies in the Jiangsu and Zhejiang plutocrats. He could only make Nanjing the capital. Even if he wanted to move the capital, he would have no time. Because he has two main enemies: the Communists from China and the Japanese. Therefore, the capital in the south was originally a result of the separatist regime's desperation or the expediency of the national regime. It can be explained from a strategic point of view without relying solely on Feng Shui theory.