People are always willing to analyze this problem from a military perspective. For example, the terrain has commanding heights in the north and offensive points in the south, so it is easier to fight in the north than in the south. For example, the ancient north occupied the land of raising horses and had the advantage of cavalry. The southern army entered the northern great plains, and it was infantry against cavalry, so it was difficult to win.
Therefore, based on this, the Ming Dynasty was able to complete the seemingly "impossible task", and Zhu Yuanzhang, the founder of the Ming Dynasty, was known as "the man who can leave the right army in Li Shimin since ancient times and follow Zhu Yuanzhang's ear", which was a rare military genius for thousands of years.
Zhu Yuanzhang and his civil servants and military commanders were really outstanding at that time, but they were able to suppress the north from the south not by military, but by politics.
There is a famous saying in clausewitz's masterpiece On War: "War is just a continuation of politics by another means". As long as it is not over-substituted, at the same level of science and technology, the victory or defeat of a war is often a political factor rather than a military factor.
Mao Haijian's The Collapse of China explains that there is a generation gap in the level of science and technology. No matter how brave and fearless, the war cannot be won. During the first Opium War, the officers and men of the Qing Dynasty were not afraid of death. From the governor and the magistrate to the general commander and the magistrate, many heroic sacrifices were made, and even the officers and men of Zhenjiang and Zhapu were sacrificed in the war. However, in the17th century, the weapons in their hands were only slaughtered against the British guns. In the Sino-Japanese War of 1894-1895, the weapons of the Qing army and the Japanese army were not replaced, but they were still defeated. That's a political issue.
Similarly, the victory or defeat of ancient civil wars often depends on the political stability and internal management efficiency of the north and south, not just on the military. Although cavalry has certain advantages over infantry, it is not absolutely invincible. As Yue Fei said: "The art of war is often fought from the rear; The ingenuity of the battle, the wisdom and will of the generals, the quality and fighting capacity of the army are the key to the victory or defeat of the war, and it is impossible to win all the cavalry.
Throughout history, although there are many wars in which the North annexed the South, there are also many wars in which the South fought back against the North. For example, the first famous North-South decisive battle in history was Battle of Red Cliffs at the end of the Eastern Han Dynasty. Cao Cao conquered the south by four to one, but suffered a fiasco. Fu Jian, the king of the former Qin Dynasty, and Yan Hongliang, the emperor of Jinfei, also suffered a crushing defeat when the army occupied an absolute majority. During the Northern and Southern Dynasties, Emperor Wu of Song Wudi led the Southern Army to cut off all the way to capture the flag, defeated the northern cavalry on the plains many times, and contacted Luoyang and Chang 'an. As for the legend of the famous white-robed general Chen Qingzhi, it can be proved that the conclusion that the cavalry will win the infantry is untenable.
The north can defeat the south, not because the cavalry is invincible. Look at what Zhou Yu, a famous Soochow player, said: "It is not China's strong point to give up the pommel horse, fight for the boat and fight for balance with Wu Yue." And the south against the north is not that the northern army is at a loss when it meets the southern army who is familiar with water warfare. Otherwise, will there be "ghosts of Wang Rui, Yizhou and the royal family have languished in Nanjing"? The key lies in politics.
Cao Cao's southern expedition failed because "the northern land was not flat", which was not enough to muster, while Sun Liu in the south was the last stop. The failure of Fu Jian's expedition to the south was due to the surrender and rebellion that unified the north, which was far from being fully digested. As a result, an inflated balloon was punctured, and the Eastern Jin Dynasty was in the period of the most stable politics and the most prosperous talents. Wan Yanliang's southern expedition failed because he had just moved to the capital, and the internal cleaning made people feel resentful. If he is slightly frustrated, he will lose everything. The instability of the post-Qin and Northern Wei regimes was a major reason why Emperor Wu of Song and Chen Qingzhi destroyed the Northern Expedition in the early stage.
The Western Jin Dynasty wiped out Wu, the Sui Dynasty wiped out Chen, the Song Dynasty wiped out the Southern Tang Dynasty, and the Yuan Dynasty wiped out the Southern Song Dynasty, all because the southern court had been alienated and could not organize effective resistance. Xie Daoqing, the last empress dowager of the Southern Song Dynasty, reprimanded his men when he joined the Yuan Army in Enemy at the Gates. This is also the common sense of the defeated parties in previous dynasties: "My heirs and I are so hard at home that I can't come up with a plan to save the current situation. Internally, I will trouble officials to leave the city, and externally, I will entrust Feng Hou to abandon the city for refuge and drag out an ignoble existence. Who is it? "
Taking history as a mirror, in contrast, the Northern Expedition of the Ming Dynasty defeated the Yuan Dynasty, which was not a great military achievement, but the reason why the Yuan Dynasty suffered from serious internal friction and lost its ability to resist.
The Yuan Dynasty was born out of the Mongolian Empire, so there was an unshakable "Mobei old system". The core of Mobei's old system was aristocratic feudalism. The monarch does not enjoy complete centralization, but wants to share imperial power with the imperial clan.
Since the ancestor Kublai Khan, the Yuan Dynasty has been trying to reverse this pattern and establish a completely centralized imperial power. One of the most important measures is to imitate the Han system, set up a prince, and deprive the aristocratic meeting "Curitai" of the power to elect an emperor.
However, historical paradoxes have also begun to appear. Since Kublai Khan's real prince, almost no prince can live to be enthroned, and the emperor still needs the support of imperial clan to gain legitimacy, which makes the centralized imperial power unstable.