In fact, this is still a big relationship between civilizations, the gap in strength, the way of fighting, the law of dynastic cycles, and the backward productivity in ancient times. During the Western Zhou Dynasty, it was still in a state of being attacked on all sides by Dongyi, Xirong, Nanyue, and Northern Di, and with the increase of the dynasty's strength, it finally pacified Dongyi, Nanyue, and Xirong. Qin Mugong even ascended to the position of overlord because of his merits of "destroying the twelve kingdoms, expanding the land for thousands of miles, and then dismissing Xi Rong". But the steppe peoples in the north are like the grasslands that blow and grow again, constantly being occupied by generations of powerful steppe tribes. This has made the northern grasslands always a major problem for the Central Plains Dynasty, and we will elaborate on the above factors below.
China is a typical land power power, in the ancient times when navigation was not developed, the eastern and southern oceans were the borders; the Qinghai-Tibet Plateau in the west was a natural national boundary, which not only became the edge of the expansion of the Central Plains Dynasty but also became the sky of conquerors such as Alexander in the West. So only generations of strong nomadic tribes that were not too high in altitude but not suitable for cultivating the northern steppes threatened the Central Plains Dynasty.
The way of civilization and climatic conditions determined that the nomadic forces in the northern steppe would become the confidants of the Central Plains Dynasty
China's ancient dynasty is a typical agricultural civilization and land power power, through the radiation of civilization and the desire for agricultural land to make the Central Plains Dynasty continue to expand its territory. When the national strength of the Shang Dynasty was still relatively weak in china' ancient Xia And Shang Dynasty, the surrounding areas were all threats: Xi Rong, Bei Di, Dong Yi, and South Vietnam, and the ancestors of Huaxia gradually expanded their sphere of influence under this circumstance. After the conquest and assimilation of the Eastern Yicheng into China in the Shang and Zhou Dynasties, the eastern territory was pushed to the sea; after the efforts of Qin and Zhao, Xirong was completely pacified; after the establishment of the Qin Dynasty, 500,000 troops were sent to the south to conquer South Vietnam, and finally the land of Baiyue was incorporated into the territory of China.
Why can the eastern, western and southern sides be included in the territory of the Central Plains Dynasty, while the northern grasslands will become a threat to the confidants of the Central Plains Dynasty? In fact, a very important reason is that it is not suitable for farming: if it is suitable for farming, with the combat strength of the Central Plains Dynasty at its peak, it has already defeated the nomadic regime, and then a large number of immigrants have been migrated to cultivate. In ancient times, a 400 mm equivalent precipitation line divided the approximate range suitable for farming, and the two superpositions of the climate zone according to the temperature verification roughly outlined the general range of the ancient dynasties: northeast, north China, jiangnan, and western region (warm temperate zone). If you use this standard to set the core territory of the dynasties starting from the Han Dynasty, it is basically the same.
Because it is not suitable for farming, the conquest of the grassland is more input than output. Even the temporary conquest of the Han and Tang Dynasties, which was as strong as the Han and Tang Dynasties, was forced to withdraw because of the continuous investment in the follow-up. The northern grasslands, although not suitable for farming, are very suitable for grazing. Therefore, such a cycle of recurrence has made the rising steppe nomadic forces become a major problem for the Central Plains Dynasty.
The way of life and the way of fighting of the nomadic regime was one of the reasons for the hidden dangers of the Central Plains Dynasty
As you can see in the chart below, nomadic areas are not endless. It is distributed in China roughly north of the Great Wall and south of the siberian high-latitude forest. Therefore, when the steppe overlords such as the Huns, Turks, and even Ruoran were defeated and the latter declined, they would move west along the nomadic belts of Central Asia and Eastern Europe to establish new empires. For example, the Attila Empire established by the descendants of the Huns and the Avar Empire established by the Jurchen descendants.
Below we analyze the reasons why the steppe regime posed a threat to the Central Plains Dynasty from the perspective of the life habits and combat methods of the nomadic people. First of all, the wealth of the nomadic people is the number of cattle and sheep, which are used to maintain their livelihoods through food and milk sources and to exchange necessary salt and other necessities. If the white disaster caused by the blizzard caused by the shortage of grassland and the large-scale reduction of cattle and sheep will cross the Great Wall to plunder the Central Plains Dynasty; of course, there is also a form similar to the Xiongnu, Turks and other self-sustaining and powerful forces, even if there is no famine, they will attack the Central Plains Dynasty's active form of provoking war to plunder wealth. For example, in the early Tang Dynasty, the Turkic Jieli Khan took the opportunity to invade the south, and plundered a large amount of wealth after the Weishui Alliance.
Let's talk about the way nomads fight, because nomads have grown up on horseback and can be said to be natural warriors. Plenty of warhorses and elite cavalry often created a fighting style in which steppe cavalry came and went like the wind. In the era when the Central Plains Dynasty was generally infantry-based, the cavalry of the steppe tribes was very mobile. To paraphrase a sentence, you can beat it, and if you can't beat it, you can't catch up. In short, the army of the Central Plains Dynasty could not stay on the grassland for a long time, and first hid in the grassland at a higher latitude to avoid it. Wait for the Central Plains Dynasty army to withdraw and then come back, so this kind of warfare based on strong mobility often gives the Central Plains Dynasty a lot of headaches.
brief summary:
To sum up, the backward productive forces in ancient times and the way of life and tactics of the nomadic regimes were the reasons for the persistence of the northern border troubles. When the productive forces entered the industrial society, the development and utilization of energy and the widespread application of thermal weapons made all this no longer a problem.
I am the emperor of history, welcome your attention; if there is a flaw, the axe is right.