After returning to his residence from the barracks, Li Yuntian solemnly took a copy of the official document on urgent military information sent from the Jingshi Military Pavilion from Lei Ting's hand, and flipped through it with an expressionless face.

At the beginning of November of the seventh year of Emperor Xuande, Emperor Xuande returned to the court from the Northern Yuan Dynasty - Hala and Lincheng Banshi, and when he passed through the Yuma River in the southeast of Hala and Lincheng, he suddenly suffered a surprise attack by a large number of Mongol troops.

Facing the Mongolian cavalry roaring on the steppe, the Ming army escorted by the Ming army was rushed to pieces, and was cut into several sections by the Mongolian army.

After a day of fierce fighting, the unprepared Ming army was defeated by the Mongol army, with many dead and wounded and captured, Emperor Xuande rushed out of the encirclement of the Mongol army under the protection of the Xiaowu army, and finally withdrew to the Great Wall after many dangers and obstacles, and stationed in Datong City.

Then, in order to ensure the safety of Emperor Xuande, the ministers persuaded Emperor Xuande to return to Beijing, but Emperor Xuande refused to return to Beijing to hide, and only moved to Xuanfu City under the repeated persuasion of the ministers, and sat in Xuanfu City to command the battle with the Mongolian army.

After being pursued and killed by the Mongol army all the way, only more than 20,000 of the 19 major armies who followed Emperor Xuande on his northern expedition were able to return to Datong City, and the rest were either killed or captured.

What is particularly tragic is that the 30,000 Xiaowu troops responsible for escorting Emperor Xuande have returned alive due to many fierce battles with the pursuing Mongol army, and the rest have been killed in the battle with the Mongol army, but they also cost the Mongol army 30,000 or 40,000 people.

It was precisely because of the desperate resistance of the Xiaowu army that Emperor Xuande was able to escape back to Datong City from the Yuma River, thousands of miles away, otherwise he would definitely be captured by the Mongol army.

After reading the official document in his hand, Li Yuntian's fists couldn't help but clench, his face was gloomy and terrifying, more than 20,000 soldiers of the Xiaowu Army died on the grassland like this, and he felt distressed when he thought about it, the Qinglong Legion of the Xiaowu Army that he had finally formed was greatly injured after this battle, and he could not recover his vitality without two or three years of recuperation.

Fortunately, Zhang Fu, the first assistant of the military cabinet, Yang Rong, the second assistant of the cabinet, and Liu Wei, the duke of Yiguo, and other civil and military officials who accompanied Emperor Xuande escaped and fled back to Datong City, otherwise the Ming court would suffer a heavy blow.

Although the attack on Emperor Xuande's Northern Expedition took place in November last year, due to delays on the way, this official document from the military pavilion was not delivered to Li Yuntian until today.

Speaking of which, it was not easy for Li Yuntian to receive this official document, the military pavilion had people carry the official document to Pyongyang Prefecture of the Korean Kingdom with the fleet of the Ming Dynasty transporting supplies, and then rushed to Kaiyuan City non-stop, otherwise because the first line of Shanhaiguan had been blocked by the Mongolian Ulianghabu, the military pavilion really couldn't spread the news to Liaodong for a while.

"Xianggong, it must have been Arutai who ambushed the emperor, it seems that they came out of the nest this time." Seeing Li Yuntian's grim face, Lei Ting said worriedly, "If Arutai breaks through the defense area of Shanxi Xingdu Division, then the Jingshi will be in danger." ”

Once the Shanxi Xingdu Division was broken by the Mongol army, then there was only one Wanquan Dusi left between the Beijing divisions, and only Xuanfu City could cause a little trouble to the Mongolian army, and the others were not worth mentioning.

Obviously, if the Mongol army breaks through the defense line of Shanxing Dusi, then it will definitely bypass Xuanfu City and approach Juyong Pass, because as long as Juyong Pass is taken, it can take advantage of the situation to go south to Jingshi and surround the imperial city of the Ming Dynasty.

In this way, the Ming army hiding in Xuanfu City can also be lured out, and the Ming army, which has lost the protection of the city wall, is definitely not the opponent of the Mongol soldiers in the field, and the Ming Dynasty will fall into an unprecedented crisis after the founding of the country.

"Shandong Dusi and Shanxi Dusi can still mobilize more than 100,000 horses, and the Mongolian soldiers are not so easy to break through Juyong Pass, they will take the opportunity to seize Datong and Xuanfu, and Chen Bing will be in front of Juyong Pass." Li Yuntian shook his head when he heard this, frowned and said, he was worried that Arutai wanted to rule with the Great Wall of the Great Ming Dynasty, so the Ming Dynasty's Jingshi would be under the front of the Mongols, and it would be difficult to ensure safety.

More importantly, the Ming Dynasty will lose the Liaodong Division, the Daning Division, and the Nuer Gandu Division, as well as the Wanquan Division, and the Shanxi Xingdu Division, which will be a heavy blow to the Ming Dynasty.

In order to strengthen the defense capability of the Beijing Division, the Ming Dynasty built two Great Wall defense lines in the north of Beijing City on the basis of the ancient Great Wall as a barrier against the northern nomads, namely the Inner Great Wall and the Outer Great Wall.

The Outer Great Wall is what people usually call the Great Wall, starting from the Yalu River in the east and reaching Jiayuguan in the west, with a total length of more than 12,700 miles, also called "outside" or "side wall".

The Inner Great Wall can be regarded as a branch that leads out from the Outer Great Wall, also known as the "secondary side", which is connected to the Outer Great Wall from end to end.

After the Great Wall entered the Gyeonggi territory from the Shanhai Pass to the west, it began to branch off at the Gunpowder Mountain north of Gyeonggi, becoming two Great Walls, one up and one down.

The Great Wall located above is the Outer Great Wall, which enters the Dushikou of Chicheng County, Hebei Province from the vicinity of Baihe Fort through Sihai Town of Yanqing, along the northwest to Zhangjiakou and Datong, to the Partial Head Pass, and finally to Jiayuguan and connects with the Inner Great Wall.

The Great Wall located below is the inner city, passing through Juyong Pass (Badaling), entering Huailai, entering the entrance to Tougou, from Lingshan out of Beijing into Hebei Zhuolu to Laiyuan to the Bauhinia Pass in Yixian County, Hebei, and then to Shanxi Yanmen Pass, Ningwu Pass and Bitou Pass, and converging with the Outer Great Wall on the east side of Baiyang Ridge in the east of Bitou Pass.

According to the history of the Ming Dynasty, "Soldiers? According to the record of "Frontier Defense", the Inner Great Wall "starts from Laoyingbao in Shanxi in the west to the south and east, and goes through Ningwu, Yanmen and Beilou to the end of Pingxingguan for about 800 miles; Turn south and east again, for the boundary of Baoding, Lilongquan, Baoma, Bauhinia, Wuwangkou, Jianling, Futuyu to the mouth of the river, about more than 1,700 li; The northeast is Shuntianjie (now Beijing City) Ligao Cliff, Baiyang, and Arrival Juyongguan, about 180 miles. All of them are steep mountains and layers, and those who are in danger are also the so-called secondary sides".

Among them, there are the famous "inner three passes" and "outer three passes" on the inner Great Wall.

The inner three passes, the outer three passes are located in the inner Great Wall line of the six famous passes, the Juyong Pass, the Bauhinia Pass, the Reverse Horse Pass on the east side are called the inner three passes, and the Yanmen Pass, Ningwu Pass, and the partial pass on the west side are the outer three passes.

These six passes are linked to each other and form a whole, which serves as a solid barrier to defend Kyoto.

Juyongguan is located in the canyon from the mouth of Badaling (North Mouth) to the South Mouth of Changping, more than 20 miles away from Badaling in the north, and forms a heavy pass with the north and south mouths.

At the beginning of the thirteenth century, the Mongol army attacked the middle capital of the Jin State, that is, the Beijing city of the Ming Dynasty, the Jin soldiers defended the Juyong Pass according to the danger, the Mongolian army then adopted the strategy of "striking the east and attacking the west", secretly moved the main force to the southwest to attack the Bauhinia Pass, and quickly moved troops from the south to counterattack the Juyong Pass, and the Juyong Pass was breached, and later the Mongolian army did not capture the Jinzhong capital and retreated.

A few years later, the Mongolian army sent troops to break through the Juyong Pass, and stationed in the Guancheng, after three years, the Mongolian soldiers besieged Jinzhongdu again, the Jin State sent an envoy to sue for peace, and the Mongolian army only left a part of the men and horses to guard the Juyong Pass.

The Jin State moved its capital to Kaifeng that year due to the threat of the Mongol army, and the Mongol army occupied the central capital the following year.

In addition, at the end of the Ming Dynasty, in the seventeenth year of Chongzhen, Li Zicheng led the army from Chang'an into Shanxi, and after capturing Taiyuan, the troops were divided into two roads, and the road led by Li Zicheng passed through Datong, Xuanhua, and broke through Juyong Pass into Beijing City, leading the Ming Dynasty to fall.

Juyong Pass is a natural danger and has been repeatedly breached, so at the end of the Ming Dynasty, Gu Yanwu heard that Juyong Pass was breached, and said with emotion: "The land is not dangerous, the city is not high, the soldiers are not many, the food is not insufficient, the national law is not good, and the people's hearts are gone." ”

Pour Ma Pass, located in the northwest of Tang County more than 150 miles, is the important pass on the "Lingqiu Road", Lingqiu Road north from Datong, over Heng Mountain, from Lingqiu along the Tang River Valley Road out of Taihang Mountain to Dingzhou.

Bauhinia Pass, located in the northwest of Yi County more than 90 miles, is an important pass at the north entrance of the "Flying Fox Trail" (one of the eight Taihang Mountains). In the second year of Jiading in the Southern Song Dynasty, Meng Yuan attacked the Jin State, and after a long time, he could not conquer Juyong Pass, but divided his troops to conquer Bauhinia Pass, and then attacked Juyong Pass from the inside of the Great Wall.

It is worth mentioning that after the orthodox emperor was captured in Tumubao, the Mongolian army entered the pass from the Bauhinia Pass to attack Beijing under the pretext of the orthodox emperor's return to Beijing.

Yanmen Pass, the city is located in Yanmen, the mouth of Yanmen of the north branch of the Luliang Mountains, the important town of Datong in the north of Jin, as far as the Mongolian Plateau, and the important town of Taiyuan in the south of Jinzhong.

Yanmen Pass is connected with the two passes of Ningwu and Yatou in the west, which is generally called "the three passes of the north of Jin", also known as the "outer three passes", and the "inner three passes" of the Great Wall on the Taihang Mountain in the west of Beijing City.

During the Northern Song Dynasty, the area from Yanmen Mountain to Hengshan Mountain was the dividing line between the Song State and the Liao State, so the Yanmen Pass was frequent, and the famous general Yang Jiye and his descendants of the Song Dynasty fought against the Liao for many years, and the main battlefield was inside and outside the Yanmen Pass.

It is rumored that there is a flat beach land with a radius of more than 20 miles in the north of Yanmen Pass, which is said to be the golden beach where the Yang family will fight with Liao.

It is bordered by the Mongolian Plateau in the north, the Ordos Plateau across the Yellow River in the west, and the Great Wall inside and outside is connected at the old camp fort in the eastern part of the country.

The partial head pass is the westernmost pass of the Ming Dynasty "outer three passes", and it is called the outer pass again, it is built in the col of the black camel mountain, the city is nearly six miles around, it is surrounded by mountains on all sides, and the shape is like a raspberry.

There are four side walls outside the pass: the first one is called the big side, more than 120 miles outside the pass, starting from the cliff head pier of Pinglu County in the east, reaching the Yellow River in the west, more than 300 miles long, there is no wall and there is a fence.

The second road is called the two sides, more than 60 miles outside the pass, from the old camp Yajiao pier in the east, to the old Niu Bay on the bank of the Yellow River in the west, to the stone ladder pass of Hequ County in the south, this side wall is actually a part of the Great Wall outside.

The third road is more than 30 miles northeast of Guan, east of Laoyingbao, west of Baidaopo, more than 90 miles long.

The fourth road is in the second mile of Guannan, starting from Changlin Eagle's Nest Mountain in the east, reaching the teaching field in the west, all brickwork, towering on the bank of the Yellow River.

In the Ming Dynasty, the defense of the Bitou Pass was extremely heavy, and it was better than the two passes of Ningwu and Yanmen.

Li Yuntian's concern was naturally that the inner three passes of the Inner Great Wall, namely the Juyong Pass, the Bauhinia Pass and the Daoma Pass of the Great Wall on the Taihang Mountain in the west of Beijing, especially the Juyong Pass and the Bauhinia Pass, were very important to the Ming Jingshi, and once it was broken by the Mongol army, it would directly threaten the Jingshi.

This means that Shanxi Xingdu Division and Wanquan Division, located between the Inner Great Wall and the Outer Great Wall, will take on the important task of blocking the southward pace of the Mongolian army, if the Mongolian army captures Shanxi Xingdu Division and Wanquan Division, then the Ming Dynasty will lose the barrier of the Outer Great Wall, and only rely on the defense line of the Inner Great Wall to stop the Mongolian army, which will undoubtedly fall into a huge passivity.

If this situation really forms, when the Mongolian army has gained a firm foothold in Shanxi Xingdu Division and Wanquan Capital Division, then there is a good chance that the Ming Dynasty will be forced to move the capital like the Jin State and return to Nanjing City.