In ancient Chinese history, the wars between the nomads in the northern steppes and the agricultural dynasties of the Central Plains never stopped, and they launched large-scale southern invasions and conquests many times, such as the Xiongnu, Turkic, Khitan, Jurchen, Mongol, Manchuria, etc. The southward invasion of these nomads has brought tremendous impact and changes to the political, economic, cultural, and social aspects of the Central Plains. So, why did the ancient northern nomads frequently invade the Central Plains in the south? What are the underlying reasons and motivations behind this?
To answer this question, we need to analyze it from geographical, climatic, economic, cultural, political and other aspects. First of all, geographically, there are significant differences and antagonisms between the grassland zone in the north and the agricultural zone in the Central Plains, and these differences and antagonisms have caused differences in lifestyles, economic structures, cultural characteristics, and political organizations between the north and the south, as well as conflicts and contradictions between the interests of the north and the south. The nomadic people of the north, mainly living on animal husbandry, depended on the fertility of pastures and the abundance of water, their way of life was flexible and simple, they did not need a fixed residence and land, nor did they need a complex social system and cultural traditions, their military strength was dominated by cavalry, which was fast and attacking, and their political organization was based on tribes, which was easy to unite and difficult to rule. The agricultural peoples of the Central Plains, mainly living on agriculture, relying on the cultivation of land and the storage of grain, their way of life is stable and complex, they need a fixed residence and land, and they also need a perfect social system and cultural traditions, their military strength is mainly infantry, slow speed and strong defense, and their political organization is based on dynasties, which is difficult to unite and easy to rule. Because of these differences, there is a relationship of mutual attraction and mutual exclusion between the nomadic peoples in the north and the agricultural peoples in the Central Plains, with the prosperity and civilization of the Central Plains attracting each other and the interests and culture of the north and the south excluding each other.
Secondly, in terms of climate, the grassland zone in the north and the agricultural zone in the Central Plains have different climatic characteristics and change laws, and these climatic characteristics and change laws have an important impact on the production and life of the north and the south, as well as on the conflicts and wars between the north and the south. The grassland zone in the north is mainly affected by the monsoon climate, the winter is cold and dry, the summer is warm and rainy, the amount of precipitation directly determines the quality of the grassland and the quantity of livestock, when the precipitation is insufficient, the grassland will appear drought and desertification, livestock will appear starvation and death, nomads will face an existential crisis, they will be forced to find new pastures and water sources, or launch plundering and invasion to the Central Plains. The agricultural zone of the Central Plains is mainly affected by the temperate climate, the four seasons are distinct, the winter is warm and the summer is cool, the amount of precipitation directly determines the harvest of crops and the reserve of grain, when the precipitation is excessive, the Central Plains will have floods and floods, crops will be submerged and rot, and the agricultural people will face the crisis of famine, and they will be forced to seek relief and relief, or launch conquest and defense to the northern region. As a result of these changes, there is a relationship between the nomadic peoples of the north and the agricultural peoples of the Central Plains, which can lead to economic crises, and economic crises that lead to conflicts and wars.
Thirdly, economically, the grassland zone in the north and the agricultural zone in the Central Plains have different economic levels and economic ties, and these economic levels and economic ties play an important role in the development and exchanges between the North and the South, as well as in the cooperation and competition between the North and the South. The nomads in the north, because they live in the steppe zone, their economic level is relatively low, their economic structure is relatively simple, their economic activities are relatively simple, their economic needs are relatively limited, their economic growth is relatively slow, and their economic development is relatively lagging behind. The agricultural ethnic groups of the Central Plains, because they live in agricultural areas, have a relatively high economic level, a relatively diverse economic structure, relatively complex economic activities, relatively extensive economic needs, relatively rapid economic growth, and relatively advanced economic development. Because of these differences, there is a relationship between economic exchanges and economic competition between the nomadic peoples of the north and the agricultural peoples of the Central Plains, with economic exchanges promoting economic development and economic competition leading to economic conflicts.
Finally, politically, the grassland zone in the north and the agricultural zone in the Central Plains have different political forms and political relations, and these political forms and political relations have an important impact on the rule and security of the North and the South, as well as on the peace and war between the North and the South. The nomads in the north, because they live in the steppe zone, their political form is relatively loose, their political relations are relatively turbulent, their political goals are relatively simple, their political methods are relatively violent, and their political stability is relatively fragile. The agricultural ethnic groups in the Central Plains, because they live in agricultural areas, their political form is relatively concentrated, their political relations are relatively stable, their political goals are relatively complex, their political means are relatively moderate, and their political stability is relatively solid. Because of these differences, there is a relationship of political cooperation and political competition between the nomadic peoples in the north and the agricultural peoples in the Central Plains, political cooperation will promote political security, and political competition will lead to political conflicts.
To sum up, the frequent invasion of the northern nomads in the south of the Central Plains in ancient times was mainly due to geographical, climatic, economic, political and other reasons, which made the northern nomads and the agricultural peoples of the Central Plains form an interactive dynamic mechanism, which includes not only the factors of cooperation and exchange, but also the factors of competition and conflict, and in different periods and under different conditions, the role and influence of these factors will change and adjust, resulting in different historical results and historical trends. Southern Song Dynasty