Since the Han Dynasty, the natural environment in the north has deteriorated, and land desertification has become increasingly serious. The once prosperous Loulan, Gaochang and Dunhuang were gradually buried by the desert. Since the Middle Tang Dynasty, especially in the period of five dynasties and ten kingdoms, the earth has entered a period of dry and cold climate. The increasing desertification in northern China has exacerbated the existential crisis of all ethnic groups living in northern China, especially nomadic peoples.

This Zhao Ta has already deeply realized that even if Lingzhou is not irrigated by the Yellow River, I am afraid it will become a desert, and from Youzhou all the way, hundreds of miles on both sides of the Hongliu River are also yellow sand, which greatly compresses the living space of the Western Xia people, forcing them to continue to invade the east, and compete with the Great Song Dynasty for arable land in the Hengshan area, migration is almost the only choice for them to face a crisis.

From these perspectives, the southward migration of northern peoples is more or less the result of climate variability. The impact of climate and human life has exacerbated land desertification in northern China and Central Asia. As a result, the living space of the vast number of nomads living in this area was greatly reduced, and the grazing space available to them was also constantly degraded, a phenomenon that was especially serious in the Song Dynasty.

Due to China's unique geographical environment, the south has become the estuary of the great rivers, so that the water resources in the south are much richer than those in the north, the vast alluvial plains formed in the lower reaches of the rivers, the fertile land is the best area for agriculture, and the temperature and other natural conditions also make the farming conditions better than those in the north, and the living environment in the south is obviously much better than that in the north.

All these natural conditions determine that the south is suitable for agricultural production and the establishment of a nation-state based on agricultural civilization. Since the Sui and Tang dynasties, the southern part of China has become an economically developed region. It gradually replaced the traditional Central Plains region as China's economic and cultural center of gravity. Migration may be the most desperate option, but this choice was not a good thing for the Great Song Empire, and the prosperity and opulence of the south did make the peoples of the north envious and salivating.

This reason is actually very simple, in the era of cold weapons, advanced civilizations often occupy areas with better living environments, while barbarians are not so lucky, and the deterioration of their living space forces them to fight for survival. Knowledge and culture are sometimes less effective than recklessness, which is the direct cause of the death of ancient Greece to ancient Rome and the death of ancient Rome to the Germanic peoples. The Song Dynasty was unable to unify the traditional Yanyun land occupied by the Liao State, but the Liao State eventually died to the Jurchens, who were even more backward and barbaric than it. Similarly, the Jin State fell to the Mongols, who were even more savage

"The people of the southeast rebelled because they were suffering from the 'flower stone' and it was difficult to survive, so they would raise their banners to rebel. In the same way, these barbarians are more dependent on the climate and environment, and their ability to withstand disasters is very fragile, and in good years, they can eat a full meal, and in the event of a catastrophe, the livestock on which they depend for their livelihood die in large numbers, and in order to survive, they have to go to the neighboring countries to survive the famine. Or even to start a war in search of a new living space! Zhao Ta said to a few people in the account.

"The area of Liao is much larger than that of the Great Song Dynasty, and there are many Jurchen talents. Isn't the territory of Liao State enough for them to toss? Lord, the Jurchens won't use troops against us for a while! Zhao Xiao drank a few glasses of wine, and his courage was also strong, regardless of Zhao Yan's pull, he boldly questioned the strategic arrangement of the prince.

"If nothing else, the Liao State could not hold out for three years, and the Jurchens became new neighbors with us, when they found that the Great Song was richer than the Liao State, and the land was more fertile, but there was no strong army to protect it. If it were you, what would you do? Zhao Ta asked Zhao Xiaodao rhetorically.

"Of course, it's going to be attacked. Grab all the good things and good places" Zhao Xiao replied without thinking about it, but halfway through speaking, he immediately realized why the prince was wary of the Jurchens.

"People's greed is more terrible than anything else, especially those who hold great power, they have to look at Shu, eat from the bowl and look at the pot, you including me have to learn to control your own **. Always remind yourself not to be greedy! Zhao Ta said, he is also reflecting on himself, his original wish when he came to this world was to be able to save his own life, not to accompany his father to suffer. Be a free prince and be content! But with the expansion of his power and the enhancement of his strength, his own ** is also constantly expanding, and sometimes even in the face of this chaotic world, he will have the idea of 'replacing it', but he knows that if he does this, it will also be at the cost of countless lives.

"It's hard to fill the craving! The prince said very well, looking at the shopkeeper Zhang every day wearing silk and satin, eating delicacies from the mountains and seas, I want to do business with them, be a businessman, and live a life of spending days and drinking, but think about when I was a child, I thought that I would grow up quickly and be a junior in the restaurant, so that I could eat the leftovers of those guests! Zhao Zhi said with a wry smile, and he was secretly ashamed in his heart.

"Ha Luha, it turns out that Brother Zhi has had this ambition since he was a child, what the prince said just now is eating in the bowl and looking at the pot is you!" Zhao said with a smile, breaking the dullness on the wine table.

"Hehe, Lord Wang, we have captured Lingzhou, and you sent Brother Yong to intervene in the battle for Xijing in Liaojin, do you also want to expand our living space?" Zhao Zhi laughed for a while and then asked.

"It cannot be said that there is no such need, strategically speaking, the capture of Yunzhou can increase the depth of our defenses, and can use geography to block the barbarians from moving south; In terms of our development, the arable and pastorable land in the northwest is decreasing day by day, and with the migration of a large number of people and the annexation of the Tibetan people, this contradiction has become increasingly prominent, which has also led to a significant increase in fiscal expenditure. Zhao Ta stopped and took a sip of water.

"Relying only on the existing land revenue must be limited, and the land tax is too heavy to support the people, too light and unable to support the regime, which can only allow us to rely on the development of trade and increase the commercial tax to make up for the shortfall, but once the Jurchens occupy Xijing, they can not only cut off our trade routes at any time by going south and occupy those fertile lands, but also threaten the Central Plains!" Zhao Ta said that he now admires himself a little, and that being in charge of the northwest has not only made a leap forward in his military ability and can command a large corps to fight, but also has an increasing sense of the overall situation, and he can consider problems from a higher level.

"Lord Wang, then we can go to the battlefield again, but it's a pity that Brother Ren and they are all leaving!" Zhao Xiao said with some excitement and sadness.

"Yes, after we return to Taiyuan, the reorganization of the army is the first priority, Zhao Zhi, Zhao Xiao, the two of you also have to return to your original position, do you have any opinions!" Zhao Ta looked at the two of them and asked, now that several commanders of the Loyal and Brave Army have left one after another, Zhao Zhi, Zhao Xiao and Zhao Yi who took over are all professional matches, and Zhao Ta has other arrangements for their development direction, and now it is time to give them a blow.

"Your subordinates obey the king's orders!" Zhao Zhi and Zhao Xiao got up together and saluted.

"Okay, let's drink this cup and create a great cause together!" Zhao Ta raised his glass and said to everyone

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