Zhao Bing conducted a series of research on Sun Wu's Yangtze River defense line because he had similar situations to the situation he faced, but after a thousand years, the situation changed. He knew that these could only be referenced, but could not be copied. However, many of the people around him were witnesses of the loss of the Yangtze River defense line of this dynasty. He also had in-depth discussions and analysis with them, hoping to get some useful things from them.

However, the results were all kinds and different. The civil officials attributed the military generals to the refusal to use their lives and rebel and surrender at the time of battle; the military generals rely on civil officials to only know internal fighting, hold on to everything, and be greedy for life and death. Some people think that powerful officials manipulate power, dismissive people, suppress good ministers and generals, and destroy the Great Wall by themselves; some people say that corruption in the court has turned into a trend, and civil officials and military generals only know how to make money in their pockets, which leads to the public's grievances, and officials do not want to serve the country, and will not be willing to serve the battlefield.

Of course, Zhao Bing also knew that they hadn't said something, but the subtext was that the emperor was stupid, appointed treacherous, wasted the country's school, and wasted his fame, but they dared not say these things clearly, and they could only think that they could not understand them. Anyway, the result was that no one was responsible, and he was the most unfair one. But he knew that the biggest reason was that the Song Dynasty was unwilling to destroy such good days from top to bottom, and would rather be content with Jiangnan, and his desire to restore the country had faded. So whoever mentioned the Northern Expedition was unlucky, and whoever wanted to restore the country would step down, this could be said to be in line with the public opinion of the whole country.

However, Zhao Bing felt from everyone's mouth that the Southern Song Dynasty's defense, Huaihe, Canal and Yangtze River played a great role in the defense of the Southern Song Dynasty in the Jianghuai area. The Huaihe River was the first line of defense, and the estuaries of the lower tributaries of the Huaihe River flowed into the Huaihe River were mostly the focus of defense, especially the Shanyang and Huaiyin areas where the Yellow River entered Huaihe River. If you seize the estuary, you can cross the river along the canal to Yangzhou. Therefore, the focus of the defense of Huaidong in the Song Dynasty was to deploy defense along the canal to the Huaihe River. Especially Chuzhou and Zhenzhou, this is the place where Huaixi and Huaidong transitioned to Nanjing, facing southwards; it is also an area where the northern army may divide its troops to attack and capture after crossing the Huaihe River from Huaixi or Huaidong directions.

The Yangtze River has always been valued by the Song court. It is not only the last line of defense that requires the Song army to take a desperate bet. At the same time, the Song Dynasty also realized that it had certain advantages on the Yangtze River and often had the possibility of turning the situation around. First, it was possible to use the Yangtze River. The garrisons in the upper reaches of Nanjing could quickly assemble to assist in defense, retreat southward and re-arrange defense north of Zhenjiang; in addition, along the canals in the south of the Yangtze River, the army in the south of the Yangtze River could gather in Zhenjiang and Taizhou; even in Jiangsu and Zhejiang could enter the Yangtze River along the coast.

Therefore, the convenience of the Yangtze River and canal channels allowed the Song army to quickly mobilize military forces in the south of the Yangtze River and even in the larger hinterland of the Jianghan Plain; of course, the materials near the wealthy Poyang Lake Plain, the Ganjiang River Basin and the Delta Plain in the lower reaches of the Yangtze River can be easily gathered to ensure military supplies; and the other is the advantage of the Song army's naval army. In the Huze and Canal areas, most of the cavalry in the north cannot be used. Although the Northern Army headed south from Huaidong and had plans to cross the river, there would not be many ships initially prepared, and more ships needed to be stepped up after reaching the north bank of the Yangtze River. In a hurry, the Northern Army's navy would not have the advantage.

Another aspect is that Zhao Bing asked about the important officials, senior military generals, and famous people in the court who were in the court, all respected the "guarding the river must guard the Huai River". He believed that in order to protect the south of the Yangtze River, it was necessary to seize the Jianghuai River and ensure the land of Jingxiang. He also did some homework in this regard, and felt that it was reasonable. The Jingxiang region and the Huai River region had superior conditions for mutual assistance and defense due to geographical convenience. This enhanced the Southern Song Dynasty's confidence and advantages in blocking the northern troops in the wide area between the Huai River and the Yangtze River.

Of course, the premise for achieving this condition is that the defense of Xiangfan in Jingxiang must be stable. Because only in this way, the troops in Wuchang and Ezhou, which were the Jingxiang aid base, including the troops in the northeastern Hubei, Qi and Shu, divided their troops from the Yangtze River and the plain area on the north bank of the Yangtze River to reinforce the war between the two Huai Rivers and the Yangtze River. Yue Fei's troops had reinforced Huaixi along the south of the Dabie Mountains.

Moreover, the troops stationed in Jingxiang and Lianghuai also had nearby reinforcements between the two places, which were the troops stationed in Jiangzhou and Chizhou. Their mission was to prevent the northern army from passing through the Dabie Mountains from the Guangzhou area north of the Dabie Mountains and sneak attacking south to cross the river from Ezhou and Jiangzhou. The Jin army did such a thing in the early Southern Song Dynasty; the other mission was to serve as a mobile force to reinforce Huaixi when it was the opportunity; it was usually an important force to stabilize the Yangtze River defense line.

Zhao Bing has not had the opportunity to visit the Jingxiang area in this life. Even now, he has only been hiking around the Yangtze River Estuary, let alone getting involved in Jingxiang. Everything can only get what he needs from the notes of his predecessors and the mouths of others, so it is more like talking about paper. However, there are no planes, and there are no satellite maps. With the ever-changing changes, everything has changed a lot from what he knows, so he can only rely on books and his own imagination.

According to Zhao Bing, there were three places that were valued by the Song people in Jingxiang area, Xiangfan, Ezhou, and Jiangling. The most important ones were Xiangfan and Ezhou. The strategic position of the latter two was particularly important in the ancient times of confrontation between north and south. When people compared Sichuan, Shu, Jingxiang and Lianghuai, they often regarded Jingxiang as the center and the middle ridge, while Sichuan and Huaii were two wings. What he didn't understand was that the large-scale wars of the Song and Jin dynasties were mostly in the Lianghuai, and the Jin army rarely placed the main force of the southern attack on the Jingxiang direction.

However, by putting together the maps of each region, you can understand the status and strategic significance of Xiangfan and Ezhou in the defense of the Yangtze River. First of all, the Two Lakes Plain is an important agricultural economic zone in the south, and Xiangfan is the northern gateway of the Jianghan Plain. Xiangfan and cities along the Han River south of it, Yingzhou, De'an Prefecture, Huangpi and others constitute the defensive support for the Yangtze River and Ezhou north. If Xiangfan is in a loss, it will be difficult to defend north of the Jianghan Plain, and Ezhou will be directly threatened.

Zhao Bing also understood that the loss of Xiangfan and the northern bank of the Yangtze River would be like a move, which would allow the Northern Army to go down the river and approach Jiankang. And along the north of the Yangtze River, it could detour to Huang, Qi, Shu and other prefectures threatened Huaixi. In this way, the defenses of the entire Huaidong and Huaixi would be destroyed without attacking. The two Huaihe troops could only retreat to the south bank of the Yangtze River and trapped Jiankang, breaking the original stalemate balance and turning into a confrontation across the river, causing the southern army to fall into a full passive position.

In addition, the Jianghan Plain was also an important economic zone of the Southern Song Dynasty. When the Northern Army completed its occupation of this area, its economic strength would be greatly enhanced, and the economic strength of the Song Dynasty would be greatly weakened, and the offense, defense and victory and loss would be determined.

In fact, even though the Yuan army was blocked many times in Chongqing Diaoyucheng and Lianghuai, once it captured Xiangfan and Ezhou, the battle between Sichuan and north of the Yangtze River was over, and the battlefield of the decisive battle of the Song and Yuan dynasties was also converted to west of Jiankang, and it was difficult for the Song army to turn the tables. Therefore, Zhao Bing felt that this battle also proved the law that Xiangfan and Ezhou remained, Sichuan and Sichuan, and Sichuan, and the two Huaihe Rivers could be safe, Jing and Xiang were lost, Sichuan, Shaanxi, and Jianghuai could not be protected.

Zhao Bing looked further and made more discoveries from the map. He felt that the Jingxiang area protected not only the Han River and the Jianghuai region south of the Dabie Mountains. In fact, the Song and Jin demarcated the boundary along the Qinling-Huaihe Line, and the boundary was not in Xiangyang, but in the Nanyang Basin and the northern foot of the Dabie Mountains. This area was still the front line for the protection of the Song army. In other words, the Han River and Dabie Mountains were not the first northern defense area of ​​the Southern Song Dynasty, and should go further north.

In this way, the importance of Xiangyang's position is not limited to the Jianghan Plain behind him, but extends forward to ensure the safety of the Han River Corridor on the left, that is, the connection between the Sichuan-Shaanxi War Zone along the Han River Corridor with Jingxiang and Jianghuai War Zones can also prevent the Northern Army from detouring from Wuguan Road to the Han River Corridor through the west side of the Nanyang Basin. At the same time, the stability of Xiangyang as a military center is conducive to the control of the Nanyang Basin by southern forces, and the importance of the Nanyang Basin for the Nanyang Basin for the management of the Central Plains is self-evident. Relying on Xiangyang, we strive to take the initiative in the Nanyang Basin, so that the Jingxiang War Zone can establish a solid cooperative defense relationship with the Huaixi War Zone on the northern foot of the Dabie Mountains.

The area of ​​defense between Jingxiang and Lianghuai in the Southern Song Dynasty was expanded, and not only passively used the terrain of Xiangyang City and Dabie Mountains to defend, but also optimized the joint defense between Jingxiang and Lianghuai, especially Huaixi. Therefore, the significance of the Southern Song Dynasty's military activities north of Xiangyang and north of Dabie Mountains cannot be ignored. The effectiveness of the military activities north of Xiangyang is to strengthen the entire Sichuan-Shaanxi and Lianghuai war zones from both sides, and the connection between the three war zones is closer, so that the Jingxiang war zone can provide timely and powerful support when the war is concentrated in Sichuan-Shaanxi and Lianghuai, especially Huaixi.

On the contrary, if Xiangfan is lost, not only will the defense on the northern foot of the Dabie Mountains no longer exist, but the situation of the Dabie Mountains as a dangerous mountain will also be lost. Not only will the army of Jingxiang have to retreat to the Wuhan River in an all-round way, but the two Huai Rivers also lose the protection on the left, and the necessity of defending north of the Yangtze River will no longer exist; the army of the two Huai Rivers will also be forced to abandon the Huai River and its vast areas south of it, and have to gather on the Yangtze River south of Jiankang, preparing to advance eastward from the direction of Wuhan along the Yangtze River and its banks.

In addition, the consequence of the Sichuan War Zone is that it is isolated. The loss of Xiangyang may cause the collapse of the Qinling defense line of the Sichuan-Shaanxi War Zone, causing the original army to retreat south to Micang Mountain to deploy defenses, and had to defend the troops from west of Xiangfan to the east, which may have been prepared to enter Sichuan from the west of Xiangfan. In this way, the defense in the Chengdu direction will naturally be severely weakened. The Northern Army can go south along the Han River and can soon threaten Jingmen and Yichang. In this way, the Sichuan War Zone will not only not be able to return to the lower reaches of the Yangtze River during the front and back attacks, but also fall into a situation of waiting for death due to the cut-off of the contact with the downstream.

Zhao Bing looked through the war between Song and Jin and Song and Meng at that time. The situation in the late Southern Song Dynasty was basically consistent with this. It is no wonder that in the middle and early stages of the Southern Song Dynasty, although the war in Xiangfan was far less tense than Huaixi, many ministers of the Southern Song Dynasty believed that the biggest defense focus of the relationship with the survival of the Southern Song Dynasty was in Jingxiang. And if this place was lost, the Song court lost not only a buffer area, but also a position to advance to the Northern Expedition to the Central Plains. He knew that after the later Huaihai Battle, the Yangtze River defense line of the Kuomintang was completely exposed, and he was eventually expelled from the south of the Yangtze River and took refuge in Taiwan.

In addition, everyone understands that fighting is to burn money, and money is not blown by strong winds. Therefore, although the layout of mountains, rivers and rivers is fixed, their military geography has different military strategic values ​​due to the differences in the relationship between economic regions, the distribution of regime boundaries and the mutual relationship between regimes. The mountains, rivers, land and dangerous areas and Guansai cities in different regions in different periods have different military strategic values.

The Jianghuai region has a developed economy, and its control over this area is not only a change in regional size, but also includes changes in important economic forces such as population and taxation within this range. Therefore, when it comes to the competition for important economic zones, the power balance between the two sides of the war is very rapid, especially when it is evenly matched, it is very obvious when fighting for an area with important economic impact. There are countless examples of this. During the Anti-Japanese War, the Eighth Route Army occupied mostly remote areas and it is difficult to achieve long-term development. However, once it occupied the Northeast, the situation immediately changed drastically, and there were no shortage of people or guns.

Similarly, the military value of Xiangfan lies in its control over the rich area of ​​Jianghan Plain. If Ezhou is lost, it will lose its economic control from Sichuan, Yunnan, Guizhou, Hunan and even Guangdong and Guangxi. On the surface, it is the fall of several cities, but the areas that bring economic losses often exceed those of simply military-occupied areas. If Ezhou falls, Jiangzhou, which is not far east, has almost no danger to defend, but the loss of Jiangzhou means the loss of the Ganjiang River Basin. Therefore, when only the economy and manpower of the Taihu Plain in the delta area south of the lower reaches of the Yangtze River are left, it is impossible to recover the defeat.

Zhao Bing actually understood that the length of the Yangtze River is thousands of kilometers. In some places with narrow river surfaces, it is actually easy to cross the river. What is important is this military buffer zone north of the Yangtze River south of the Huai River. If the Huai River is lost, the Yangtze River will be difficult to protect. Therefore, there is also a military saying that "the limit of the Yangtze River cannot be sustained for a long time." The situation he is facing is that not only does not have the Jianghuai River as a buffer, but there is not even a foothold on the north bank of the river. Theoretically, the Yuan army can attack them from any point.
Chapter completed!