Chapter 161 Exploration

Defensively.

It is a kind of city defense fortification, the purpose is to prevent the enemy outside the city from sneaking over the city wall by digging tunnels underground, and then attack from the inside without anyone noticing.

Back then, Xiyun City also wanted to dig defensive tunnels, but after discovering that the city walls were covered with hard rock layers, they gave up on this plan.

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

The defensive tunnel requires extremely delicate design and construction. On the one hand, it needs to support the thick soil layer above so that it will not collapse when large troops pass by on the ground.

On the other hand, when the enemy army is digging the tunnel, as long as they accidentally dig out any of the support points, the entire defensive tunnel will have a chain reaction like dominoes, and then collapse, preventing the enemy from attacking. The purpose of sneaking into the city from underground.

It is said to be a support point, but it is not the obvious wooden stakes, but the support points are integrated into the entire passage in a very ingenious way by skilled craftsmen.

There may be at least three to five such support points hidden in the mountain walls on both sides of a passage of about 100 steps. As long as the enemy army accidentally destroys the mountain wall while digging the tunnel, it is very likely that they will cut off the support points in the middle. Support point, so as to produce a chain reaction.

If a collapse occurs in the tunnel, it goes without saying that it can cause serious consequences.

Especially in a big main city like Bo'an City, a moat was excavated under the city wall. If the defensive tunnel below the river bottom was dug and broken, the river weighing hundreds of tons would be almost useless once it fell down. chance of survival.

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

If it wasn't for Chen Ze leading the army to the side of the main city gate, Xu Qing and the others saw the rusted tunnel gate with their own eyes, they probably would have forgotten that there is such a tunnel in Bo'an City.

Chen Ze brought people here, of course he wanted to leave the city through the defensive tunnel.

This kind of defensive tunnel actually has another name, it is called the escape channel.

Once the defenders were unable to withstand the powerful offensive from outside the city and the city would be destroyed, the high-level officials in the city could rely on this passage to escape outside the city and save their lives.

There is an exit leading to the outside of the defensive tunnel. Not only is this exit extremely secretive, but there are even more organs inside the exit. People inside can go out, but people outside cannot enter through it. It is a one-way passage. .

Seeing that Chen Zezhen had plans to sneak out of the city through the defensive tunnel, Xu Qing couldn't help but look worried.

It is true that the tunnel can allow people to go out of the city, but it is too narrow after all, it is true that a small number of people can pass through, but a large army of more than 30,000 people like them has too many people and the speed of passage is too large. It is bound to be slow and time-consuming.

Secondly, there are too many people and hands. This defensive tunnel has not been used for many years. It is afraid that it will be more fragile after being in disrepair for a long time. Xu Qing is afraid that if someone accidentally damages one of the support points, the moat above his head will be flooded. If it is smashed down, you will drown if you don't get smashed to death on the spot, which is absolutely unreasonable.

You must know that there are no blueprints for this defensive tunnel. Only the craftsmen who built the tunnel knew the entire layout and support points, but that was at least a hundred years ago. The secret was leaked out, and it was claimed that those craftsmen were tightly protected, but who knew what was going on behind the scenes.

Chen Ze got his head in, and it is very likely that he will not be able to get out.

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

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

That's the problem with the air.

The tunnel is very narrow, if there is insufficient ventilation and too many people flood into his side at one time, there is no guarantee that there will be no problem of suffocation and death.

And when he ordered someone to open the tunnel gate that time, the damp and stuffy air that hit his face made him come to a conclusion.

Being located at the bottom of a moat, dampness is inevitable, but the smell is very faint. Not only that, but there is also a continuous breeze gushing from the tunnel, which proves that there are many other vents in this defensive tunnel.

Thinking about it, this passage also shoulders the heavy responsibility of providing escape passages for the high-level people in the city. Naturally, it is impossible for the high-level people to suffocate to death in the tunnel.

That's why Chen Zecai led the troops here, otherwise, he would have to go around the inner city gate of Bo'an, and spend at least three more days to get out from the low mountains on the side.

That would also achieve his plan, but the longer it took, the less benefit he would get from it.

As for what Xu Qing was worried about, there was no problem with Chen Ze.

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

The military exploits of buying general star fragments are naturally enough. With this breath, Chen Ze directly strengthened Cheng Yu until the duration soared to five hours, which was almost equal to that of Ma Teng before stopping.

Immediately, his eyes turned, and he smiled at Li Quan'an, who had just flashed a touch of purple in his eyes: "Then you will lead the way?"

"I obey!"

Li Quan'an clasped his fists in response without any hesitation, and took a large backpack, a small red flag and torches that he had prepared earlier from the soldier next to him, and entered the gate with a slight bow.

Chen Ze stayed outside for a while, and organized the 30,000 soldiers behind him. Several of his confidants, including Gu Qingfeng and others who had just signed the entourage documents, were all called together by him.

"Each one of you will lead a section, and I will give you an emphatic order. Once you see such a small red flag in the tunnel, you must never touch the place marked by the red flag!"

He held several other red flags in his hand and distributed them to various people one by one. Then he personally led a group of sword and shield fighters and entered the gate with torches in hand.

Xu Qing and the others looked at each other in blank dismay. It can be seen that Chen Ze was so confident that he was the first to go in by himself, so they didn't say anything more. According to Chen Ze's order, they divided the remaining 20,000 people into separate groups. Waiting outside the gate to get in.

As for Xu Qing's concern about the tunnel being destroyed unintentionally, the key lies in the little red flag.

The person Chen Ze possessed for Li Quanan was naturally Cheng Yu's general.

One of Cheng Yu's three general skills is insight, which is a powerful ability that can see through the enemy's ambushes and weaknesses in advance.

Since Cheng Yu entered the tunnel first, even if he didn't have blueprints in his hand, he could still distinguish the hidden support points in the tunnel with his own ability.

When one is found, a small red flag is planted. 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.