In terms of strategy, everyone knows that Zhao Kuangyin's decision to establish the capital Kaifeng was a wrong decision, and he also realized this, and had intended to move the capital to Luoyang, and even the imperial tomb chose Gongyi, which was closer to Luoyang. However, due to his violent death and the opposition of the ministers led by Zhao Kuangyi, it was never completed, which also laid the groundwork for the demise of the Northern Song Dynasty.

The Great Wall was not built in a day, and the awkward location of Kaifeng was not built in a day. In order to avoid the invasion of the Qin State in the west, and to advance eastward at the same time, the capital of the Wei State was moved from Anyi to Yiyi, called "Daliang", and the history of Kaifeng City began. After the three families were divided, the Wei State seemed to be strong, but in fact it was full of crises, and if Han and Wei were in trouble, Hexi would be lost to Qin, and in the east, they would be defeated by Qi, and the Wei State would turn from prosperity to decline.

However, at that time, the terrain of Kaifeng was low and flat, and it was easy to accumulate water and become waterlogged. After King Wei Hui built the capital, he successively carried out a series of water control and diversion projects in Kaifeng City. It diverts the water of the Yellow River from Xingyang into the nursery field, then opens a big ditch, leads the water of the nursery field to flow eastward, passes through the north of the city of Daliang and then turns south into the Yingshui and the vortex river, forming a gap canal that communicates the two major water systems of the Yellow River and the Huai River.

This chasm has played an incomparable role in the fate of Kaifeng's city, so the beam has become the center of the water transport network extending in all directions, the navigability of each river has been greatly improved, and the girder has become the hub of water transportation in the Central Plains because it is located in the center of the chasm water system. The formation of the so-called "north from Yanzhao, south to Jianghuai, waterway metropolis, the situation is rich". This leads to the southern lands, and in the event of a rebellion in the south, the Liang state can resist first.

In addition, after the construction of the chasm, it also improved the flood discharge capacity of the Kaifeng area, eliminated the nearby stagnant water, improved the irrigation conditions of farmland, and promoted the agricultural production and economic development of the Wei State. In just a few decades, the vicinity of Daliang became a major agricultural area for the Wei state, and the Wei regime was thus consolidated. And also posed a threat to the city, and later the Qin general Wang Ben could not attack the Liang for a long time, so he led the water of the chasm to irrigate the city, and after a hundred years of prosperity, the city of Liang was tragically destroyed, and the Wei State also perished.

After the establishment of the Sui Dynasty, in order to strengthen the north-south material transportation capacity, the Sui Dynasty excavated the Tongji Canal, starting from Luoyang, leading the valley water and Luoshui to the Yellow River, after a section of the Yellow River, the Yellow River water was diverted southeast in Banzhu, passing through the city of Kaifeng, to the north of Xuyi County, Jiangsu Province into the Huai River, communicating the political center of the north of the country at that time, Chang'an Luoyang, and the Huaiyang area, the land of fish and rice, and gradually became a rich vascular center. Bianzhou is located at the throat of the canal, has a prominent position in the transportation of grain, and ushers in a new vitality.

In addition to the hub status of water transportation, Kaifeng in the Tang Dynasty was also the hub of land post roads. After traveling eastward from Xi'an to Luoyang, and then east, northeast, and southeast, there are three main post roads, two of which must pass through Bianzhou. In particular, the lower reaches of the Yangtze River Delta and the Jianghuai region, which were important places for the Tang Dynasty at that time, must pass through here. Since then, Bianzhou has actually begun to gradually become an important city of domestic water and land transportation and a general checkpoint of the country's economic lifeline.

After the Anshi Rebellion, in order to avoid the capital being trapped due to the interruption of transportation, the Tang Dynasty set up the Xuanwu Army here to rebuild the city of Bianzhou, and Bianzhou became a military town in the Central Plains. In the late Tang Dynasty, the economic development level of the Yellow River Basin and the Yangtze River Basin became more and more disparity, the north became more and more dependent on the financial resources of the south, and the status of Bianzhou became more and more important. At that time, people said: "The girder is the most important thing in the world, the complexity of the boats and vehicles, the throat of the river Shuo, and the transportation of the Huai Lake."

At the end of the Tang Dynasty, the Xuanwu Army stationed in Bianzhou made Zhu Wen usurp the power of the Tang Dynasty and establish the Later Liang Dynasty, with the capital Bianjing and called the Eastern Capital. Kaifeng once again became the capital of the country. Among the regimes that changed after the Later Liang, in addition to Luoyang, the Later Jin, Later Han and Later Zhou all took Bianzhou as their capital and called Tokyo. At the beginning of the Later Jin Dynasty, Kaifeng established the status of the capital, and among these dynasties, the Later Zhou Emperor Zhou Shizong had a more far-reaching influence on the transformation of Kaifeng City.

Zhou Shizong not only re-planned and built Kaifeng City, built Kaifeng New City, expanded the outer city, and widened the city streets, but also paid attention to the construction of water conservancy, dredged the Bianhe River, and restored the previous water and land transportation network centered on Kaifeng. The construction of Tokyo City in the Later Zhou Dynasty laid the foundation for the urban layout of Tokyo in the Northern Song Dynasty, and opened the way for Kaifeng to replace Luoyang and become an administrative center city, and Kaifeng's status as the capital was easy to consolidate.

After entering the Song Dynasty, although Chang'an and Luoyang were devastated in successive wars, Kaifeng had the opportunity to rise rapidly during the Five Dynasties period and become the political, economic and cultural center of the Central Plains, but when it was really time to put it into action, Zhao Kuangyin did not hesitate. It is true that Kaifeng has developed water and land transportation, which is conducive to controlling the vast Kanto region, and after the construction of the four dynasties during the five dynasties, the city and palace have been relatively complete, but there are no hidden dangers here.

From a geographical point of view, there is almost no danger to defend around Kaifeng, which is a typical "place of four wars", and it is very unfavorable as the capital of a country. In order to make up for the weakness of Kaifeng's geographically unfavorable defense, the Song Dynasty had to make up for it by stationing heavy troops in the capital. Abandoning the capital of Chang'an or Luoyang, the Northern Song Dynasty began to focus on the development of Kaifeng, an important water city. At that time, there were Huimin River, Bianhe River, Wuzhang River and Jinshui River passing through the city of Tokyo in Bianliang, Tokyo, and it was known as the "Four Waters Guandu". Tokyo has become the center of the four rivers of the Bian, the Yellow River, the Huimin River and the Wuzhang River.

The Bianhe River, a branch of the Yellow River, brought prosperity to Kaifeng, but the Yellow River has always been a hidden danger. Since the Northern Song Dynasty, the amount of sediment carried by the Yellow River has accumulated significantly in the river, and it has been changing its course to the south to approach Kaifeng, and the dense waterways near it have also become the best channel for the Yellow River to discharge floodwater.

The repeated flooding of the Yellow River caused the "Four Great Transports" in the Northern Song Dynasty, which was dominated by the Yellow River and the Bianhe River, to be silted up due to the flooding of the Yellow River, and also changed the ecological environment in the region, making the surrounding area of Kaifeng, which was once called the "Northern Water City", a vast sea of sand. The frequent wars in the later period made the Yellow River diverted many times, and broke many times in the Kaifeng area, and then the Mengyuan moved the Grand Canal further eastward, and changed to the southwest of Lu instead of passing through Henan, so that the decline of Kaifeng was out of control.

As a modern person, Zhao Yu knows more that from the southward migration of the Song dynasty to the end of the Qing Dynasty for 700 years, the Yellow River went south to seize the Huai River and entered the Yellow Sea during this period, and the flood broke in Kaifeng and its adjacent areas more than 100 times, at most once a year, and at least ten years. Since the Yuan, Ming and Qing dynasties, Kaifeng City has been flooded by the Yellow River seven times. The most serious one was when Li Zicheng besieged Kaifeng, and Gao Mingheng, the governor of Henan in the Ming Dynasty, opened a river embankment in the northwest of the city in a vain attempt to drown the rebels. The flood rushed into the city from the north gate, the water and the city were level, the whole city was swallowed up by the flood, there were few buildings left in the city, and Kaifeng became an underground city again.

Such geographical conditions naturally deeply affected the development of Kaifeng City. When the Jindu was opened, the Bianhe River was still partially navigable. At the beginning of the Ming and Qing dynasties, there was only one navigable river, the Jialu River, and its shipping starting point was no longer in Kaifeng, but moved to its outer port - Zhuxian Town. After the Qing Daoguang, the Jialu River was also silted up due to the flooding of the Yellow River many times, and Zhuxian Town also declined. Although land transportation was once known as the "Eight Provinces Tongya", the actual scope of attraction was mainly limited to Henan Province.

At the same time, the sediment of the Yellow River has also salinized the fertile plain farmland near Kaifeng, to the point of "the former abundance and salinization alkali brine". As a result of the destruction of the water transport network, Kaifeng, which developed first by virtue of its status as a water transport hub, will inevitably plummet and be reduced to a regional political center, and in modern times, it has been replaced by Zhengzhou, and the ancient capital has finally become a third-tier city.

Zhao Hao, who has known for thousands of years, originally had a fluke mentality about Kaifeng, but now he has not yet arrived in Kaifeng, and the surrounding situation has made him understand that the old capital is no longer the old capital of the past. In the current military situation, the main force of the Mengyuan army around Kaifeng has either been annihilated or has been surrounded, and the remnants are only some Tuntian troops and a small number of Zhenfu troops.

First of all, in terms of the military situation, the Eastern Route Army has basically completed the strategic objectives set at the beginning, while the Western Route Army has arrived in Xiangyang, but it has not been able to recover it for a long time. As a result, there were too many fronts in the east, forming a huge salient, and many states and counties in the surrounding areas were not recovered and consolidated, forming many gaps, if the enemy army concentrated its forces from the gaps to the rear, detoured back to the rear of the Eastern Route Army, and at this time the main forces of the Song army were concentrated on the front line, there was no time to return to help. Therefore, at this stage, the Eastern Route Army must stabilize the newly acquired land, close the gap, and not give the enemy a chance to take advantage of it.

On the other hand, the war in Sichuan and Shu was still ongoing, and because of the inconvenient transportation, the battle report could not be transmitted back in time, which made Zhao Hao unable to grasp the battle situation in time, and he did not dare to act rashly. If the attack on Shu fails, Xiangyang will also face the danger of being attacked on the belly and back, and Zhao Hao's launch of the Northern Expedition and the attack on Shu is also to improve the defense system of Jiangnan and change the passive strategic situation. Xuzhou, Xiangyang, and Chongqing are the three important nodes of the entire defense system, and if they are not stable at all, there will be huge loopholes in the entire system, and there is a danger of collapse.

Moreover, Kaifeng is the place of four wars, and it is already a consensus that it is not conducive to defense. After the reconquest, a large number of troops were needed to garrison it, which would inevitably overstretch the Song army, which was already insufficient in strength, and lose its strategic mobility capability. In addition, the continuation of the Northern Expedition, which remained unfinished in terms of military preparations, and most importantly was the lack of cavalry. After crossing the Yellow River, it was the North China Plain, and it was difficult for an army lacking mobility to gain an advantage, so Zhao Yu also needed time to expand and train cavalry, which took time to do

Of course, in addition to the military, there are also many issues such as politics, economy, and people's livelihood, and Zhao Hao also needs time to rectify them......