Chapter 161

Defensive tunnel.

It is one of the urban fortifications. Its purpose is to prevent the enemy outside the city from sneaking across the city wall by digging tunnels, and then attack from the inside without being aware of it.

At the beginning, Xiyun City wanted to dig a defense tunnel, but it gave up after finding that there were all hard rock layers under its wall.

But this does not prevent Xu Qing, the former chief of urban defense, from knowing the existence of this fortification.

The defense tunnel needs extremely exquisite design and construction. On the one hand, it needs to support the heavy soil layer above so that large forces on the ground will not collapse.

On the other hand, when the enemy excavates the tunnel, as long as they don't pay attention to digging any support point, the whole defense tunnel will have a chain reaction like dominoes, and then collapse, so as to prevent the enemy from sneaking into the city from underground.

It is said to be the support point, but it is not the obvious wooden pile, but the support point is integrated into the whole channel by skilled craftsmen in a very clever way.

There may be at least three to five such support points hidden in the mountain walls on both sides of a hundred steps or so. As long as the enemy accidentally destroys the mountain wall when driving a tunnel, it is very likely to chisel off the support points in the middle, resulting in a chain reaction.

In case of collapse in the tunnel, it is needless to say that it can cause serious consequences.

Especially in the major cities such as bo'an City, a moat has been dug under the city wall. If the defensive tunnel at the bottom of the river is cut off, the river weighing hundreds of tons will hardly survive.

As long as conditions permit, most cities will dig such a defensive tunnel around their cities. Over time, the generals in charge of attacking the city will no longer choose to attack in the way of tunnels, and these defensive tunnels will gradually be ignored.

If Chen Ze hadn't led the army to the side of the main city gate, Xu Qing and others had seen the rusty tunnel gate with their own eyes. It is estimated that they would have forgotten that there is such a tunnel in bo'an city.

Chen Ze brought people here, of course, to get out of the city through a defensive tunnel.

In fact, there is another name for this kind of defensive tunnel, which is called escape passage.

Once the defenders cannot resist the strong offensive outside the city and the city will be broken, the high-rise in the city can rely on this channel to escape outside the city and save their lives.

There is an exit outside the city in the defense tunnel. This exit is not only built very secretly, but also equipped with organs inside the exit. People inside can go out, but people outside can't enter. It is a one-way passage.

When Xu Qing saw that Chen zezhen was planning to sneak out of the city from the defense tunnel, she couldn't help but look worried.

It's true that the tunnel can accommodate people out of the city, but after all, it's too narrow. It's true that it can allow a small number of people to pass through. But for large troops with more than 30000 people, such as them, there are too many people, so the traffic speed is bound to be slow, time-consuming and laborious.

Secondly, there are many people and hands. This defensive tunnel has not been used for many years. It is even more fragile when it is in disrepair for a long time. Xu Qing is afraid that if someone accidentally damages one of the support points, the moat river overhead will fall down and drown without being killed on the spot.

You should know that there are no drawings for the defensive tunnel. Only the craftsmen who built the tunnel knew the whole layout and distribution of support points, but that was at least hundreds of years ago. Moreover, even at that time, after bo'an City repaired the tunnel, in order to prevent secret leakage, it claimed to protect the craftsmen closely, but who knows what happened secretly.

Chen Ze's head will probably not come out if he goes in.

This is Xu Qing's concern, but it is not within Chen Ze's consideration.

He came to see it once before and solved another problem he was really worried about.

That's the air problem.

The tunnel is very narrow. If there is insufficient ventilation in it and too many people pour into it at one time, it is difficult to ensure that there will be no suffocation and death.

When he ordered people to open the tunnel gate, the wet and stuffy air let him have a judgment.

Located at the bottom of the moat, dampness is inevitable, but the smell is very weak. Not only that, but also the continuous breeze gushes out of the tunnel, which proves that there are many vents in the defensive tunnel.

Think about it, this channel also shoulders the important task of providing escape routes for high-rise buildings in the city. Naturally, it is impossible for high-rise buildings to suffocate in the tunnel.

That's why Chen Zecai led his troops here. Otherwise, he would have to go around the inner gate of bo'an and spend at least three more days climbing over the mountains from the low side of the mountain.

In that way, he can achieve his plan, but the longer it takes, the less benefit he can get from it.

As for Xu Qing's worry, Chen Ze has no problem here.

After ordering people to open the gate again, Chen Ze was silent for a moment, but strengthened Cheng Yu's generals in the system again.

The battle merit of buying Jiangxing fragments is naturally enough. Chen Ze's breath directly strengthened Cheng Yu until the duration soared to five hours, almost equal to Ma Teng.

Then his eyes turned, and Li Quan'an, who had just scratched a touch of purple at the bottom of his eyes, smiled and said, "then you will lead the way?"

"Yes, sir!"

Li Quan'an answered with a fist and did not hesitate. He picked up a large backpack, a small red flag and a torch prepared too early by the soldiers next to him, bowed slightly and entered the gate.

Chen Ze stayed outside for a moment and coordinated the 30000 soldiers behind him. Several of his confidants, including Gu Qingfeng, who had just signed the entourage document, were called together by him.

"You each take a section and give orders. Once you see such a small red flag in the tunnel, you must not touch the place marked by the red flag!"

He took several other red flags in his hand and distributed them to all kinds of people one by one. Only then did he personally take a team of knife shield hands and enter the gate with torches.

Xu Qing and others looked at each other. It can be seen that Chen Ze was so confident that he took the lead in entering by himself. They would not say more. According to Chen Ze's instructions, they took the remaining 20000 people separately and waited outside the gate according to the queue.

As for Xu Qing's worry about the tunnel being inadvertently damaged, the key is on the small red flag.

Chen Ze's attachment to Li Quan'an is naturally Cheng Yu's general.

One of Cheng Yu's three generals is a powerful ability to see through the enemy's ambush and weakness in advance.

Cheng Yu advanced into the tunnel. Even if he didn't have a drawing in his hand, he could distinguish the hidden support point in the tunnel with his own ability.

If you find one, insert a small red flag. As long as the people behind do not touch it, they will not damage the support point, and naturally there is no danger of collapse.