Looking at the map, Zhao Hao sighed lightly, this expedition to the west is not only a long and arduous road, but also has to break through the enemy's layers of obstacles. As far as he knows, Sichuan Province was one of the ten provinces of the Yuan Dynasty with a relatively strong military color, and the troops stationed in the territory included the Mongol Army, the Tanma Red Army, the Han Army, and the New Army, and the number was huge, maintaining about 45,000 people, and reaching 75,000 at the most.

However, after Kublai Khan conquered Jiangnan, he began to streamline the new army and adjust the garrison in the 20th year of the Yuan Dynasty. This wind also spread to Sichuan, merging the three provinces of Xichuan Eastern, Western, and North Propaganda Divisions and Tongchuan and other roads to guard Wanhu Mansion, the New Army Governor's Office, Weizhou, Guanzhou, Maozhou and other places to pacify the 14 Divisions. Military power in Sichuan was gradually centralized, institutions were gradually streamlined, and the administrative and military and political centers began to shift to Chengdu.

Zhao Hao's strategic focus has always been in Jiangbei, but Sichuan and Shu live in the upper reaches of the Yangtze River, and he also regards it as a sharp knife pierced behind him, so he did not relax the monitoring of the situation in Sichuan and Shu, and ordered the Affairs Bureau to set up a Sichuan and Shu intelligence station to investigate this area and collect military and political intelligence. According to the information sent back, the main towns in Sichuan are:

Chengdu: Chengdu was an area occupied earlier by the Mongol and Yuan armies. During the reign of Ögedei Khan, Prince Kuoduan entered Chengdu and occupied the western part of Sichuan. After plundering a large number of supplies, the Mongol army abandoned Chengdu again. During the period of Meng Ke Khan, the army led by Liu Heima and Jiagu Longgu reoccupied the abandoned city of Chengdu. Möngke Khan attached great importance to the defense of Chengdu and sent his generals to hold heavy troops here.

When Kublai Khan seized the throne of Khan, he regarded it as a great danger to his henchmen and "punished him with an edict". However, after seizing the throne of Khan, Yuan Shizu appointed Yuan Zhen, the son of the dark horse who made meritorious contributions to the secret power of fire, as the head of the Chengdu Economic Strategy and sent heavy troops to garrison it. In the fourth year of the Central Unification, Li Pingyang's "winged army in Xichuan returned to Chengdu in Qingju Mountain." ”

Before Kublai Khan launched a full-scale war to destroy the Song Dynasty, Chengdu was an important city for the Song and Yuan dynasties. Zhongtong asked in the year that the Song army once attacked Chengdu, but it was only saved because of the joint defense of Sichuan Xingyuan Atuo and Zhang Wanjianu. In the tenth year of the Yuan Dynasty, the Song Dynasty blamed Wanshou for attacking Chengdu. At that time, the Chengdu garrison army was also attacking Jiandu with the general, and the defense was empty for a while. The Yuan court had to sign a new army for aid on "Jingzhao and other roads". After the destruction of the Song Dynasty, the Yuan court still attached importance to the defense of Chengdu, and in the twenty-third year of the Yuan Dynasty, it divided the Sichuan town garrison army into Chengdu Tuntian. In addition to completing the defense mission of Chengdu, the Chengdu garrison also participated in the pacification of the southwestern turmoil on many occasions.

Chongqing: In the fourteenth year of the Yuan Dynasty, Xichuan Xingyuan led the army to besiege Chongqing, and Zhao An, the capital of Song and Chongqing, surrendered. Song Shouchen Zhang Jue fled east of the river to Fuzhou, and then surrendered. The Yuan court also attached great importance to the defense of Chongqing, and successively set up the Propaganda Department, the Imperial Academy, and the Provincial Government. In the first year, the emperor's grandson Temur did not spend a time to garrison Chongqing. In the twenty-fourth year of the Yuan Dynasty, General Huaiyuan and Kuilu Wanhu Shi Mo Dog Dog Army in Chongqing.

After the Song court recovered Jiangnan, Chongqing was once again valued by the Yuan army, which threatened Jiangnan along the river, and retreated to prevent the Song army from going up the river to attack Sichuan and Shu, threatening Yunnan and the Shaanxi-Gansu region. Therefore, he moved the province of Sichuan to Chongqing, and only set up the Xuanwei Division in Chengdu, and transferred the ruling center from Chengdu to Chongqing, and gradually stabilized. In addition, the garrison of the Propaganda Division was set up on Kuizhou Road, Luzhou, Jiading and other roads around Chongqing to defend, and at the same time, Tuntian was used for military use.

There was turmoil in Yunnan, and it was difficult to calm down for a long time, Zhenjin transferred Chongqing five roads and ten thousand households from Sichuan Province to save Yunnan, but as soon as the army and horses arrived in Yunnan, they were ambushed by various barbarian tribes and lost more than 10,000 soldiers. Therefore, the Yuan court felt that Chongqing still had adjustable military horses, so this year it transferred 2,500 troops to Chongqing and Xuzhou to quell the rebellion, and at the same time sent 2,000 troops from the princes and vassals in the neighboring provinces of Sichuan to defend Chongqing.

As a result, the garrison of the Yuan court in Sichuan was greatly reduced, and the various armies under the Xuanwei Division were only more than 40,000. After synthesizing the intelligence of all parties, Zhao Hao thought that the opportunity was rare, and Lingxiao City was still in the hands of the Song army, so he decided to launch a westward expedition in the name of rescue to restore the defense system in the Chongqing area. In this way, you can relieve your worries and get support points in the Sichuan and Shu regions.

After Zhao Yu decided to go west, he took the opportunity of the coming dynasty at the beginning of the year to discuss with them, and all the generals thought that it was not easy to fully seize Sichuan and Shu under the current situation, but should restore the defense system of Yu Yu in the Chongqing area, so that the advance could be attacked and retreated, and the first invincible position could be defended, and then adjusted according to the changes in the situation. The generals' discussion coincided with Zhao Yu's idea, so they collected intelligence and formulated a battle plan based on it.

Since Chongqing had been lost for more than ten years, and the status of a series of fortresses built by Yu Yu was unknown, Zhao Yu ordered people to secretly investigate, and also looked for insiders and former participants to inquire about the situation, so as to conduct targeted training and preparation. After some investigation, the situation is basically clear, Yu Jue built a series of fortresses from north to south, the main fortresses are:

Qingju, located in the north of Shunqing Mansion, a northern city in Sichuan, in the middle reaches of the Jialing River, it guards the northeast of Sichuan and becomes the seat of Shunqing Prefecture. Da Gain, in the southeast of Cangxi City, Yu Yu moved to Langzhong Prefecture to govern here, originally built by the famous general Wang Jian, is the northeasternmost fortress in the hinterland of Sichuan. Kuzhu Pass, at the top of Xiaojian Mountain in the west of Jianmen Guanxi, is the gateway to the north of Sichuan. Shenjian Mountain is in the east of Luzhou, or Tielu Mountain, and Yu Yu moved to Luzhou Prefecture to govern here.

Duogong City, forty miles west of Chongqing, the purpose of building this fort is to defend the periphery of Chongqing. Yunding is in the northeast of Chengdu Jintang County, Yunding Fort is the nearest fortress from the Chengdu Plain, playing a peek at Chengdu without danger to defend, and it also plays a role in choking the water outside the Jialing River - the Fujiang River, and together with Diaoyu to prevent the Mongolian army from trying to take advantage of the Jialing River Boat Division, the plan to attack Chongqing downstream.

Hutou, Hutou Mountain Fort is in the southwest of Fushun in southern Sichuan, and is the northern barrier of Luzhou. Xiliuguan, in the northwest of Wanzhou, guards the Yangtze River waterway and Kuimen in the lower reaches of Chongqing. Diaoyu, Diaoyu City is in the suburbs of Hezhou, more than 100 miles away from Chongqing in the north, at the confluence of the three rivers of Didangqu River, Fujiang River and Jialing River, choking the internal water of Jialing River, the seat of Hezhou Prefecture, it guards the only land passage in Chongqing.

In addition, there are dozens of large and small forts, which are connected end to end, from the northern and western Sichuan to the eastern and southern foothills of the basin group of southern and eastern Sichuan, leaning on the main rivers of Sichuan, forming a network to block the Mongol army from attacking the middle and lower reaches of the Yangtze River in the east.

Looking at the fortresses built by Yu Jue, it can be found that they all have a common characteristic, that is, the mountains are steep, but not too high, generally the relative ground height difference is tens of zhang meters to 100 zhang, the top of the mountain is more flat, often close to the water's edge, especially the kind of hill close to the river. Such forts often make it difficult for the enemy to climb with a simple traditional siege ladder, and the enemy must connect the ladder quite high, so climbing the ladder becomes very dangerous, and it is easy to be overturned or broken by the defenders, as happened later when the Möngke army attacked Diaoyu City.

The fort is mostly flat, suitable for stationing troops and civilians, and many fortress mountains have springs, and the spring water on the Diaoyu Mountain can even be used to raise big fish. The proximity to the river facilitated the interconnection and logistical connection between the forts. Finally, the relative height difference is not large, and the difficulty of attacking and making up also avoids it. Diaoyu Mountain can be said to be the best site, it is at the intersection of the three rivers, the height is about 100 zhang meters, there are nearly 100 springs on the mountain, inexhaustible in winter and summer.

In Jiading Mansion, it is also fortified with nine tops and three turtles and purple clouds, forming a three-chain fortress to defend Jiading. Jiading Mansion was originally a place where two rivers meet, there are mountains and rivers, which is conducive to defense, and the water and land are convenient, down to Luzhou, and up to Chengdu, in this way, in addition to the fortress, Yu Jue and Jiading, Luzhou, Chongqing three big cities together.

Later, with the change of the war situation, Yu Jue implemented the strategy of tightening the front, shrinking the heavy troops originally stationed on the southern slope of the Qinling Mountains and defending Sichuan at the edge of the Hanzhong Basin back to the outer circle of the Diaoyu-Chongqing-Luzhou-Jiading arc defense, and used Qingju Fort and Dahoubao as the vanguard to peep into the Xingyuan Mansion and Qinlongshan District, which had now fallen into the hands of the Mongol army, and made a posture of attacking Xingyuan at any time; With Jintang's Yunding Mountain as a bridgehead to peek into the former provincial capital Chengdu, not far from the bottom of Yunding Mountain, is the famous Jiantan ferry on the Fujiang River, which blocks the attack of Mongolian iron cavalry on Chengdu.

In the end, Yu Jue built forts from Zhaohua to Jianzhou in northern Sichuan as the outermost part of the defense. It can be seen that the strategy of the Sichuan fortress group to defend the Mongol cavalry is the whole chain, they have a clear main and secondary, close to the mountains and rivers, and have only one purpose, to defend the Yangtze River waterway and prevent the enemy from going down the river to the east and attacking the south of the Yangtze River.

To meet such site selection conditions, there are not many places as large as a province in China. In fact, not many of these forts were directly captured by military means, and most of them were lost due to the rebellion of the defending generals. In addition, these forts were both military fortresses and political centers, and their most important key was the Diaoyu Fort on the outskirts of Hezhou, without which there would be no Chongqing, and without Chongqing, the Southern Song Dynasty's power in Sichuan would be completely lost.

Not only that, politically, Yu Jue also ordered the Yu Xingbu stationed in Jiading to be stationed in Tuntian, Chengdu Plain, as soon as Chengdu was breached, the people on the Chengdu Plain lost the management of the government, but now the fortress of Jiading and the Yunding Fortress can carry out remote control of Chengdu, and the military reclamation farms of the troops on the plain can also play a role in stabilizing the people's hearts and strengthening ties with local political power.

In addition, Yu Jue also carried out the policy of lightly dispensing the people of Sichuan with a light burden and promoting education, he punished officials who did evil, and the arrogant soldiers and fierce generals who ran away when they heard the enemy were also removed and suppressed, and established discipline and prestige in the Sichuan garrison. During the eight years he was in charge of Sichuan, Yu Yu was able to achieve great governance in Sichuan under the military situation of confrontation with Mongolia, so that "the enemy did not dare to approach the border, and the year was great."

In Zhao Yu's view, Yu Jue's actions can be called textbook-like achievements, not only through eight years of governance, Sichuan has restored its prosperity, but also sent a large amount of financial endowment to the central government, reducing the financial burden and military pressure downstream. In the winter of the tenth year of Chunyou, when the situation in Sichuan improved, he led the generals to patrol the border, smashed the Xingyuan on the Hanzhong Plain, and fought with the Mongol army.

After that, in the twelfth year of Chunyou, the Mongolian Wang Dechen led the army to loot Chengdu and attack Jiading, and Yu Yu led the defenders of Jiading to fight with the Mongolian army in Jiading and drove them away. In the 36th battle between Sichuan and the Mongolian army, the enemy was beaten into a few strongholds, and a large number of rural towns and villages were still under the management of the grassroots power of the Southern Song Dynasty, so that the enemy could not fully control Sichuan......

In order to gain a favorable situation, Zhao Yu ordered the Hu Guangzhi Division to launch several small-scale operations, regain Guizhou, and capture Zigui and Badong, two important towns in the south of the Yangtze River. But his eyes were on the Three Gorges upstream at this time, and the previous series of battles were only a drizzle compared with the next battle for the Three Gorges, which was the key to determining the victory or defeat.

The Three Gorges is known as the most spectacular and breathtaking scenery in the Yangtze River, and the magic of nature and hundreds of millions of years of heaven and earth creation have made this unique natural landscape gallery. But for the people in the boat, there is no poetry in the eyes of the literati, but a veritable ghost gate, sailing in such a canyon, the cliffs are towering, and the river waves crash on the shore, which makes people thrilling.

The Three Gorges River is full of dangerous and unpredictable waters, and the dangerous shoals and rocks are all obstructing ships crossing the Gorge. The water of the Three Gorges is urgent, thousands of waters are rushing to Kuimen, and the waves in the gorge are stormy. The river water drop is large, and the reefs in the river are dense, making it difficult to sail. The water level soared by more than a dozen zhang in one day, and the water level changed greatly within a year.

And the width of the river is different, the wide place is surging, and the narrow place is only ten zhang when the water is dry. The depth of each section of the river is also different, the deepest part is nearly 70 or 80 zhang, and the shallow part of the water is less than 6 or 7 zhang. The river is the undercurrent vertical and horizontal, the whirlpool is small like a bucket, the diameter of the big one is nearly ten zhang, the depth is more than zhang, once the ship is involved in it, it is difficult to escape the doom of the ship's destruction and death. In the past, the merchants of Sichuan and Shu often went down the river with boats and ships full of goods to do business, but after arriving in Jiangnan, they sold them together with the ships and goods, and people chose to return to Sichuan and Shu by land, and the reason was that they were afraid of the danger of the Three Gorges.

The Three Gorges is located in the middle and upper reaches of the Yangtze River, with the Yangtze River waterway in the east, and can go down to the Jingzhou Plain, the Jianghan Plain and the land south of the Yangtze River, and can pass through the Central Plains and enter the Guanzhong. At the same time, the Three Gorges also has the conditions to block and close off Sichuan and Shu, and it will inevitably be a battleground for the soldiers of all dynasties to defend and attack against danger. Offensive campaigns were carried out in this area, that is, to destroy the military fortifications of the Three Gorges and break through the natural dangers of the Three Gorges. And its natural geographical location also determines that the mode of warfare usually adopts the mode of water warfare and mountain warfare, and the strategic pattern of the defender can only be defense-oriented......