Although the mainland has a long history and has gone through many dynasties, the dynasties that have been unified are only the Qin, Han, Jin, Sui, Tang, Yuan, Ming, Qing, and other dynasties. Among these unified dynasties, the Han dynasty accounted for the vast majority. However, the territory of the great unified dynasty established by the Han people was obviously inferior to that of the Mongolian Yuan and Manchu Qing dynasties. For example, although the territory of the Tang Dynasty reached its peak during the period of Emperor Gaozong of Tang, this extremely prosperous territory lasted only four years; the territory of the Ming Dynasty reached its peak during the Zhu Yuanzhang period, but by the time of Ren and Xuan, it had begun to shrink in an all-round way. However, the extremely prosperous territories of the Mongolian Yuan and the Manchu Qing Dynasty lasted for a long time.
Many people believe that this is because the military of the Mongolian Yuan and Manchu Qing dynasties was the most powerful in history. In fact, this is not the case, according to the horizontal comparison of the same period, the military of the Mongolian Yuan and the Manchu Qing dynasty is not the strongest in history. Although Mengyuan fought invincible hands all over the world for a period of time, Mengyuan's life expectancy was only one hundred years. The Manchu Qing military decayed even faster, and the combat effectiveness of the Eight Banner Soldiers, which the Manchu Qing was proud of, had been greatly weakened since the Manchu Qing entered the pass, and the destruction of the Southern Ming and Ping San Fan had mainly relied on the Green Battalion, and after entering the modern era, it was only beaten. The military superiority of the Han Dynasty and the Ming Dynasty over the surrounding countries and nationalities was maintained for nearly three hundred years. So why did the Han Dynasty build a dynasty that was no larger than that of the Mongol Yuan and the Manchu Qing?
First, the Han people's concept of the world. In the past, scholars and doctors always mentioned "cultivation, qi, governance, and peace", and many people believed that these were only the four stages of self-cultivation. However, in the pre-Qin period, classes were relatively solidified and not very mobile. "Repair, Qi, Governance, and Peace" actually correspond to the four classes of the nobility. At that time, the territory of the "Son of Heaven" was called "Tianxia"; the fiefdom of the "princes" was called "Guo"; the Caiyi of the "Doctor" was called "Home"; and the "Shi" had no fiefdom and could only support himself by becoming a priest (needing self-cultivation). Therefore, this peaceful world corresponds to the Son of Heaven, the rule of the country corresponds to the princes, the Qi family corresponds to the doctor, and the cultivation corresponds to the scholar.
Before modern times, the "country" in the mouth of the literati doctor actually referred to the "county" (county), and the "tianxia" in the mouth of the literati doctor actually referred to Huaxia, that is, China. The so-called "pacification of the world" mentioned by the founding monarchs of those dynasties refers to "pacification of China". That is to say, in the Han concept of "tianxia", "tianxia" does not actually include the surrounding "barbarians". In the concept of "under the heavens" of "barbarians", this "world" is "barbarian + Huaxia". Therefore, the "tianxia" in the Han concept is naturally smaller than the "tianxia" territory in the "barbarian" concept.
Second, the "barbarian lands" of the past did not have much attraction to the Han people. During the reign of Ming Taizu Zhu Yuanzhang, at that time, Japan was rude to Daming, and Zhu Yuanzhang still had to endure anger and listed Japan as one of the countries that would never be conquered. This was not because Daming lacked the military strength to conquer Japan at that time or that Zhu Yuanzhang had the virtue of a good life and was unwilling to act rashly. Instead, Zhu Yuanzhang believed that there was no profit in conquering Japan, that there was not enough land to cultivate, and that there was not enough people to make it. The conquest of Japan was nothing more than a waste of money and food, and the blood of soldiers was shed in vain.
We are an agrarian people, and historically we have not had much interest in unsuitable farming areas, nor do we have the conditions to develop them. The living territory of the Han people was basically laid during the Qin Dynasty. We can find that the "Eighteen Provinces of Guannei" and the Liaodong part inhabited by the Han people in the late Qing Dynasty are roughly equivalent to the territory map of the Qin Dynasty.
In history, the conquest of the Xiongnu, the annihilation of the Turks, the conquest of the Mongols, and so on, were too much out of strategic security considerations, rather than the inducement of interests. Although the Han and Tang surrendered to the Xiongnu and turks, they could not live in their places. The result can only be that the grassland has changed its master, and the Xiongnu, Xianbei, Rouran, Turkic, Uighur, Khitan, Jurchen, Mongol, Jurchen, etc. have always been the greatest threat to the Chinese Dynasty.