If you want to say that in the zhou, qin, Han, and Tang dynasties, where it was most suitable to build a capital city, it is natural to talk about the place of Chang'an.
First of all, For a long time in the past, Chang'an was the first choice for various dynasties to build capitals. According to some statistics, it is not difficult to find that in China's feudal society, Chang'an must have its place in Chang'an, which was chosen as the capital for the longest time. Before the establishment of the Song Dynasty, there were twenty-one dynasties and regimes in Chang'an. Even after the success of Li Zicheng's peasant uprising, he established the capital in Chang'an.
Secondly, Chang'an has a deep history and experience in the construction of the capital. The size and area of the capital city of Chang'an is comparable to that of the capital of the Tang Dynasty and the imperial palace of the Ming and Qing dynasties. And this laid a good foundation for Chang'an as the capital.
However, after the end of the Tang Dynasty, except for Li Zicheng, who still chose to build the capital Chang'an, all dynasties and generations no longer chose Chang'an as the capital of a country. The location of the capital is also constantly migrating from south to north and from west to east.
Of course, where the capital is located is a major affair of the country and requires double consideration. However, in the long history after the end of the Tang Dynasty, the reason why all dynasties no longer chose Chang'an as the capital of their own dynasties was because at this time, Chang'an's advantageous conditions as the capital of a country disappeared.
So, why?
Some people think that from the geographical point of view, the location of Chang'an is a bit west.
Because the territory of the later dynasties is constantly expanding, the location of Chang'an is difficult to control the place, so it is not suitable for the development needs of the times. However, this view is also problematic, and although geographical location is important, it is not the decisive factor. The establishment of a national capital is the result of a combination of factors, so it cannot be simply thought that it is the lack of geographical location that makes Chang'an lose its advantage.
As a result, some people believe that Chang'an lost its opportunity as the capital of the country because of economic problems.
From the middle of the Tang Dynasty, the economy of the south developed rapidly, almost on a par with the economy of the north, and after that, China's economic center of gravity shifted south. The location of Chang'an is more inclined to the northwest, making the transportation of materials very inconvenient. From a certain point of view, this view also has a certain correctness, but it still does not analyze the reasons for Chang'an's loss of the status of capital as a whole.
During the Tang and Song dynasties, the southward shift of the economic center of gravity was a fact, but the shift of the economic center of gravity did not represent the shift of the political center of gravity. From the Yuan, Ming, and Qing dynasties to the present, China's political center of gravity remains in the north.
Therefore, economic reasons are not the only reasons.
If we look deeply into the reasons behind this, we can find that in addition to the geographical location, the rapid growth of the southern economy is the reason. In fact, the reason why Chang'an lost its status as the capital of a country after the end of the Tang Dynasty has to mention the factor of war.
The first time Chang'an was destroyed was the Hojing era of the Western Zhou Dynasty, and the history textbooks say that king Youwang of Zhou, in order to amuse the beauty of the people and praise the princes, made a beacon drama of princes, and as a result, became the most famous "wolf came" in ancient times, and finally, Xi Rong attacked the pickaxe capital, killed the king of Zhou You, and also abducted the king of Zhou, and the western Zhou perished. The capital could no longer be built in this area, and the Zhou royal family moved to Luoyang in a gray and slippery way.
The second time Chang'an was destroyed was in the last year of the Qin Dynasty, and now parts of Xi'an and Xianyang were collectively known as "Xianyang" at that time, and Xiang Yu directly set a fire after coming over, destroying the imperial city painstakingly operated by the Qin Dynasty into a pile of coke. It is said that the self-confident Qin people at that time did not build a city wall in Xianyang, because they believed that Tongguan in the east, Dashanguan in the west, Xiaoguan in the north, and Wuguan in the south were the natural walls of Xianyang. In other words, in the eyes of the Qin people, their capital city is the entire Guanzhong!
The third destruction of Chang'an was after Wang Mang usurped the Han Dynasty, Wang Mang also died in the rebellion, and Chang'an, which Zhang Liang had called "the golden city of a thousand miles, the kingdom of heavenly palaces", was also abandoned by the Han Dynasty due to devastation. The fourth destruction of Chang'an was at the end of the Eastern Han Dynasty, and this story is also told in the Romance of the Three Kingdoms: the rebellion of Li Dai and Guo Feng (Dong Zhuobu general) left "no trace of the Guanzhong region for two or three years". The fifth destruction of Chang'an was during the Three Kingdoms period, to a lesser extent, and the Western Liang warlord Ma Chao took advantage of Cao Cao's lack of preparation to attack Chang'an...
The sixth destruction of Chang'an was during the Western Jin Dynasty, the seventh destruction of Chang'an was in the last year of the Sui Dynasty, and the eighth destruction of Chang'an was during the tang Xuanzong period. It can be seen that most of the dynastic changes before the Tang Dynasty occurred in the northern region, especially near the capital city of Chang'an. The Anshi Rebellion dragged down the Tang Dynasty, and since then, for more than a hundred years, although Chang'an City has been destroyed many times, it has been repaired in time. However, by the end of the Tang Dynasty, the foundation of Tang dynasty rule was unstable, and the power to suppress resistance was getting weaker and weaker, so that Chang'an City was more and more seriously damaged.
Later, during the reign of Emperor Dezong of Tang and Emperor Wuzong of Tang, the peasant revolt burned down the palace after successfully invading Chang'an City. After that, the warlords emigrated on a large scale, demolished the houses and streets, and burned the palace and most of the houses. Chang'an City was in the midst of such fireworks, and all the glory of the capital city was like yesterday, it suffered a major trauma, and it was crippled and withered. Since then, Chang'an has not become the capital of any dynasty. After that, the time came to the five generations period, and the change of regime was unusually frequent.
During this period, many battles, large and small, took place. Chang'an City, which was originally a ruined city, had not yet been restored, and it had experienced the damage caused by war after war. By the time of the Song Dynasty, the Jin Dynasty had attacked Jingzhao (present-day Xi'an) and slaughtered the Han Chinese. It can be said that it was these destructions that accelerated the decline of Chang'an City. And all this makes it difficult for the Guanzhong region to rise. After the iron horse of the Mongols, this time not only Xi'an, it is said that 90% of the Han civilians in the north were tragically genocided, and the most unfortunate thing is that Sichuan, a neighbor of Shaanxi, was slaughtered, ten rooms and nine empty...
However, the decline of Chang'an City, in addition to the war, there is another important factor: the environment.
According to the records of the literature, Chang'an City was originally a place with rich products and ecological harmony. Not only are there many rivers and irrigation sources plentiful, but the land is fertile. However, during the Sui and Tang dynasties, the population here increased dramatically, and in order to feed more people, they had to reclaim the land, and the demand for firewood also rose greatly. After that, people began to deforestation indiscriminately, unceasingly reclaim wasteland and pollute water sources. These behaviors, to a certain extent, affected the ecological environment of Chang'an City.
Since then, the climate of Chang'an City has become harsh, floods, droughts, etc. have continued to occur, and even the cultivated land has become no longer fertile. After that, the ecological environment of Chang'an City became very bad and fragile.
All of the above factors have accelerated the decline of Chang'an City to varying degrees, and together these factors have made Chang'an lose its great advantage of becoming the capital of the country. However, it should be noted that although, after the last years of the Tang Dynasty, Chang'an is no longer the capital of a country. However, due to its rich history of the capital city in the past, the rulers of successive dynasties regarded Chang'an City as a very important strategic place.
Resources:
【New Book of Tang Dynasty, Geographical Chronicle", "Zizhi Tongjian", "Chang'an Zhi"】