Li Chao stood in Loufu Guancheng and inspected this Guancheng with Su Dingfang and others.
Next to it is the eldest princess of Pingyang, who arrived one step ahead of Li Chao, she has taken over the post of governor of Lanzhou, and Lou Fuguan is a prominent part of the northeast of Lanzhou, sandwiched between Shuozhou and Daizhou.
"Dashuai, Lou Fuguan is located on the Huagai Mountain of the remaining veins of Heng Mountain, Linhui River, overlooking the east, west and south three sides, the circumference is four miles, and there are three gates of east, west and south.
After Li Ji and Li Jing, two generals, the town guards the river from time to time before and after, now the city is five miles around the city, the city base is five zhang, the neck is two and a half zhang wide, and the city is more than three zhang high.
In addition, there is the periphery of the city, rammed earth to build the city, the circumference is seven miles, the north gate is added, there is a flying tower on it, the name Zhenshuo Lou, because the building is as high as the winged phoenix, so it is called the Phoenix City again. ” Standing on the high city wall of Loufu Pass, overlooking the north, you can see far away.
This Guancheng, the north and south are narrower, the east and west are long, now there are two double Guancheng inside and outside, the circumference is more than seven miles, the city wall is tall and strong, the arrow towers are scattered all around, the enemy towers are dotted around.
The inner city wall has been increased from the original three zhang to four zhang.
Several city gates are also covered with bricks, and a towering moat is also built on the top of Huagai Mountain in the north of the city.
There are three floors of heavy buildings on the fort, which is called Huagai Building.
This building is not only connected to the Inner Great Wall, but also built a 40-mile-long side wall in the north of the city.
The reason why Li Chao knows these things very well is because the reinforcement plan of the entire Lou Fu Pass was originally made by him.
The Tang Dynasty did not build the Great Wall, but the northern Turks were powerful, so at the beginning of Li Shimin's ascension to the throne, Li Chao entered a northern defense plan to Li Shimin.
He suggested that the two generals, Li Ji and Li Jing, should guard Hedong and Hebei, and at the same time focus on building several passes in Hedong, Hebei, as a defense against Turkic fortresses.
Li Chao's fortress plan is to take the internal and external three passes of the Ming Dynasty as the core.
Li Shimin read the plan and carefully discussed it with Li Chao, and finally adopted this suggestion, and did not go to overhaul the Great Wall, but focused on strengthening the internal and external three passes.
The focus of the Tang Dynasty's defense in the north is no longer a line, but six points.
Lou Fu Pass, is one of the three foreign passes of the Ming Dynasty Ningwu Pass.
Ningwu Pass is called Lou Fu Pass at this time, so this place was the Lou Fu tribe in ancient times.
During the Warring States Period, King Wuling of Zhao once set up a building here to prevent the Huns.
During the Northern Wei Dynasty, the two counties of Guangding and Shenwu successively ruled this, and in the Sui Dynasty, they belonged to Lao County and Jingle County.
At this time, the Tang Dynasty, the imperial court placed Lanzhou, and Loufuguan belonged to the territory of Jingle County, intersecting with Shuo and Dai Erzhou.
Later, Tang placed Ningwu County, which was the beginning of Ningwu Pass, took the tail word of Guangning and Shenwu County, but at this time, it was also called Lou Fu Pass.
However, although it is called Lou Fu Pass, its defense, after the two years of Li Ji and Li Jing's two generals have been reinforced, the danger of this pass is not lost to Yanmen.
Li Chao originally proposed the three internal and external passes of the Northern Great Wall, the outer three passes are the partial pass, Yanmen Pass, and Loufu Pass, and the inner three passes are Juyong Pass, Bauhinia Pass, and Reverse Horse Pass.
The outer three passes, that is, in the northwest of the northeast of the river, the inner Great Wall line connected by Shou Bitou, Ningwu and Yanmen Passes, is a huge barrier that spans 500 miles in the north of Jin, and makes use of the dangerous terrain of the Great Wall and Hengshan in the past.
Different from the concept of operating the Great Wall in previous dynasties, Li Chao's defense plan for the three internal and external passes in the north, although it is also based on the Great Wall, is not a linear defense, but a defense cluster with several important nodes as the core, and the corners of each other in all directions are mutually supportive, which is a point-shaped defense network.
The Turks dominate the north, especially in the situation of occupying Daibei and Hetao, Hedong and Hebei, are the most vulnerable directions to attack and break through, once they break through the line of the Great Wall, they can enter the plain area, especially the Hebei Plain, if the Turks are allowed to enter the Hebei Plain, the vast plain area is extremely difficult to defend against the Turkic cavalry.
For this reason, Li Chaocai put forward this defense plan for the three internal and external passes in the north.
He abandoned the past practice of two defensive layers of the inner and outer Great Wall, and instead formed two lines in the east and west of the north, and changed the northern and southern defense layers to the east and west defense layers.
In the northern part of the Taihang Mountains in Hebei, three passes of Bauhinia, Reverse Horse and Juyong are set up along the line, and fortress clusters are established with these three passes to form a deep defensive circle and protect the Hebei Plain.
In the east, west and north of the river, set up the three passes of the head, the building annoyance, and the Yanmen, which are the outer three layers, and the outer three passes are the first layer of defense clusters.
Li Chao's defensive focus of the internal and external three levels is actually in Hebei.
The three internal and external passes are heavily guarded, which is to ensure that the Turks cannot break through into the Hebei Plain through the Hetao and Daibei, which are the advance bases of the Turks.
Under this kind of thinking, he would rather let them break into the central part of Hedong than let them enter the Hebei Plain.
The defense task of the outer three passes is extremely heavy, the head is closed at the extreme edge, the Yanmen is rushed, and the building is annoyed by the second pass, the head of the border pass is controlled, and the situation is extremely heavy.
The Turks have always thought that the center of gravity of Datang's Hedong defense is Yanmen Pass, but in fact, they don't know that Datang's northern defense thinking has long changed.
The imperial court used heavy troops to garrison the Loufu Pass, so as to facilitate the east to guard the Yanmen, the west to aid the partial pass, and to the north can also go out of the clouds.
Li Chao pointed to the continuous valley and said to Pingyang and Su Lie, "The geographical location of Loufu Pass is extremely special, especially in the current situation occupied by the Turks, if they want to go south, they must pass through three passes.
There is a desert Gobi in Shuofang, and it is inconvenient to attack there.
Therefore, it is mainly to go south to the east, and to go south from this side, you must pass through three passes. ” "Among the three passes, the Yellow River is a natural hazard in the partial passes, so the Turks who came from the Hetao can only step on the ice in winter.
And Yanmen Pass, with the mountain as a natural danger, it is difficult for the cavalry to break through.
Only Lou Fu Pass, although there is a Hui River, but the Hui River is a seasonal river, and there is a period of interruption every year, so in the autumn season, the Turkic cavalry can advance south along the river valley and reach the pass. ” The valley of the Hui River is relatively wide, and Li Jing's report to the imperial court said that ten horsemen can be allowed to advance together.
It is precisely because of this unique reason that the middle road building in the outer three levels has become an easier node to break through.
It's just that now the Turks don't know that many fortress clusters have been built here, and Loufu Pass has become a war fortress with seven miles around and two layers of inner and outer gates.
Compared with the linear defense of the Great Wall in the past, the point-shaped fortress defense cluster has an advantage in that it can support operations more independently and is not easy to break through.
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Compared with the linear defense of the Great Wall, this defense method is far inferior to the Great Wall for small groups of steppe cavalry to raid and plunder.
Because the Great Wall is fully defended, a small force of cavalry cannot break through the wall or break through.
Only when a large number of steppe cavalry moves south, the Great Wall will appear weak, and Gaokou, the Great Wall, and the pass will be difficult to cope with a large number of cavalry.
The point-shaped fortress cluster built by Li Chao is different, the focus is on the fortress and the surrounding dungeons, etc., it is point-type, there will be a gap in the middle of the castle, and a small group of cavalry can easily infiltrate it, if they just come to rob, they can't completely defend it.
But if it is to defend against a large force of cavalry, these fortress groups can support each other and support the defense, and it is difficult to be breached for a while.
Ningwu Pass City is very large, but it is only the south entrance of Ningwu Pass, and there is a north entrance in the north more than 20 miles. t1706231537: