With Cloud City as the center, within a radius of dozens of miles, it is desolate and inhabited, the cold wind is bone-chilling, and there is a desolate and dead atmosphere everywhere, and the villages and tribes in the distance are all gray, and there is a ruined atmosphere everywhere.

After entering Li Feng's strong wall and wilderness, and the Hu people burning, killing and looting, this huge northwest grassland, only the soldiers and civilians of Yunzhong City and the Hu invaders outside the city were left, and the rest of the place was a dead silence.

After the bloody battle during the day, the entire Yunzhong City seemed to be a lot quieter, and there was silence on the Hu tent, and those Hu people did not seem to have any plans to attack at night, but were recuperating and preparing for the siege battle of Ming.

However, in the midst of the terrible cries of the night owls, under the darkness, hundreds of Hu people wrapped in thick cotton clothes, under the leadership of Zhang Wu, took advantage of the night to quietly move closer to Cloud City.

It was night, it was dark, and only a faint halo was emitted around the hairy moon, which made the night appear more deep, teaching people to see the surrounding situation clearly, so these Hu soldiers slowly approached the city in the clouds, and did not attract the attention of the defenders in the city.

"This is it, you move lightly, and you must not be discovered by the defenders of the city." Zhang Wu's face was gloomy, he wore a short drama on his waist, and he glanced around vigilantly, and after seeing that there was no abnormality, he also commanded in a low voice.

Hearing this, those Hu people also nodded, and immediately took out shovels, shovels and other tools, and slowly excavated.

This location, located in the northwest corner of Cloud City, is located in the middle of nowhere, and it is surrounded by dense weeds, which is just enough to hide the figure of the Hu people and not be discovered by the defenders of Cloud City.

At the same time that Zhang Wu led the Hu people to dig tunnels, above the head of Cloud City, Zhao Fan and Xu Jia were also discussing what measures the Hu people would take to capture Cloud City.

Xu Jia glanced at the situation under the city with a calm face, and because the night was dark, he didn't find anything abnormal, and immediately said: "Authentic, Gongzi should know that if the Hu people attack the city in this way, it will be really troublesome."

The tunnel is to dig a hole leading to the city wall, and support it with wooden piles, and then either launch a surprise attack into the city, or dig a tunnel directly under the city wall, and erect wooden piles on the hollowed out places, and when the city is attacked, the wooden piles are set on fire with firegrass, and the wooden piles lose their support and collapse naturally. ”

It is mentioned in the "Preparation of Caves" that in order to prevent the enemy from digging the foundation of the city and burning the city walls, it is necessary to build tall buildings in the city, send scouts to monitor the movements of the besieging enemy army at night, and at the same time, if the water of a well in the city is found to be muddy, it may be that the enemy army is digging a hole.

However, it is the cold winter season, it gets dark early, and this time is just the beginning of the month, and there is no bright moon at night, even if you send troops to hold on to it at night, you may not be able to see it clearly, so Xu Jia will say that if the Hu people dig the tunnel, it will be a little troublesome.

Hearing this, Zhao Fan also nodded, according to the current situation, digging tunnels is indeed an effective siege method for the Hu people, and it is relatively difficult to find.

At this moment, Zhao Fan's heart moved slightly, a smile appeared on his face, and said: "Xu Jia, I only say that you are talented and knowledgeable, how can you forget the best weapon to deal with the enemy's tunnels?" ”

Xu Jia looked puzzled, in this regard, it was the first time he heard that there was a weapon that could prevent the enemy from digging tunnels, and he was immediately confused: "What kind of weapon?" Why haven't I heard of it before? ”

Feeling Xu Jia's doubts from the bottom of his heart, Zhao Fan couldn't help but be slightly stunned, could it be that this kind of device had not appeared in this era, but he remembered that among the materials he learned in his previous life, this was indeed from the Warring States Period.

"Listen, haven't you heard?" Zhao Fan was slightly stunned, and seeing that Xu Jia still looked puzzled, he also explained: "Ground listening is a reconnaissance tool to listen to the enemy's tunnels. When the defenders of the city discovered that the enemy was digging tunnels and attacking from underground, they immediately placed a special thin cylinder in a deep well at the foot of the inner wall of the city, and the mouth of the cylinder was covered with a thin layer of cowhide, so that the hearing people lay down on the cylinder and listen to the enemy's movements. This detection method has a certain scientific reason, because the sound of the enemy's excavation of the tunnel propagates from the ground quickly, the sound wave attenuation is reduced, and it is easy to resonate with the cylinder, which can be used to detect the enemy's position and distance. It is said that the sound of enemy digging tunnels can be heard within 500 steps of the city. ”

Hearing this, Xu Jia realized and said: "I see, this method is indeed effective, I didn't expect Gongzi to come up with such a wonderful idea, so, I am not afraid of the Hu people digging tunnels and attacking Cloud City." ”

Seeing Xu Jia say this, Zhao Fan also shook his head, it seems that during the Warring States Period, he did not appear to listen to this kind of reconnaissance tool, in his previous life, he remembered that this kind of reconnaissance tool first appeared with "Mozi. Preparation of acupoints", if you look at it this way, this article should not be from the hand of Mozi, otherwise how could Xu Jia not have heard of this kind of tool.

Just as the Analects was not written by Confucius, this Mozi should also be a biography of Mozi written by later generations, so it is reasonable that there are some deviations in it.

In the ancient war, the city defense facilities often take the setting of the ground listening as an important item, dig a deep well every certain distance around the city, generally the well is two zhang deep, put a drum-shaped new urn, the listener can listen to it in the well holding the urn, so it is called "urn listening" again. People who have watched the movie "Tunnel War" may still remember that there is such a scene: in order to prevent the soldiers and civilians from resisting the Japanese army, the devil led the tunnel to the bottom of their stronghold, and he placed a large vat deep in the courtyard to listen to the movements underground. This is where ancient listening came in.

Seeing that Xu Jia had never heard of this kind of reconnaissance tool, he immediately explained: "The earth can detect whether the enemy is digging a tunnel, once it is determined, we can dig from the city opposite the enemy's tunnel, and then stuff in a series of two feet five inches long and three feet thick tile tubes, the tile cylinders are covered by two tiles above and below, and the gaps between them must be tight."

Place carbon and chaff in the tile tube, but do not stuff it, build a stove at the entrance of the hole, open two bellows outside, there is a partition in the hole, while digging, while pushing the partition forward, when approaching the enemy's cave, that is, quickly break through the soil layer, and then ignite the fire in the stove, agitate the bellows, in order to smoke the enemy. ”

This kind of smoked enemy created by digging tunnels was extremely popular in ancient times, Zhao Fan didn't expect that during the Warring States Period, he had not yet invented this kind of siege equipment, and immediately shook his head slightly.

Fortunately, the production method of the ground listening is very simple, only a thin jar of the same size as the import, and a piece of raw cowhide, it is not how complicated, Xu Jia got this method of restraining the enemy from digging tunnels, and immediately ordered people to find some thin jars and raw cowhides in the whole city.

This battle was a key battle between the Hu people and the Zhao people, so Zhao Fan and Xu Jia didn't dare to be careless, and immediately ordered someone to find a thin jar from the city and a piece of raw cowhide.

Zhao Fan and the others were lucky, and it didn't take long for them to find this thin tank from a private household, although it was not special, but it was just right to put down a well under the city, and immediately, the two of them also walked down the city with a team of soldiers.

After placing the thin jar in a deep well under the city wall, Zhao Fan immediately covered it with raw cowhide and said, "Later, you will take turns to put your ears on the cowhide and listen, if there is a strange sound in the well, notify us immediately." ”

This listening has been proven feasible by thousands of years of practice in ancient times, so Zhao Fan is not worried that it will be useless, and the method of judgment is also very simple, as long as there is vibration from the raw cowhide, and there is an abnormal sound, it can basically be concluded that the enemy is digging the tunnel.

Zhao Fan still doesn't know what kind of siege methods the Hu people are going to take to capture Yunzhong City, but no matter what the Hu people do, they must prepare in advance and strangle all the siege methods that may be used by the Hu people.

Therefore, when he ordered people to be familiar with the ** to listen to the ground, Xu Jia also ordered people to prepare for the construction of wooden buildings on the city wall, and also resisted the suppression and siege methods that the Hu people might use.

A soldier in armor with a curious look in his eyes, under Zhao Fan's instructions, slowly put his ears up to listen to the piece of raw cowhide.

This was the first time he had seen this kind of new thing, so he was inevitably a little curious, and at the same time had a touch of doubt about the true effect of listening to this place, after all, many people's first feeling for new things is that they are not reliable.

"Buzz!"

As soon as the soldier put his ears on the raw cowhide, a vibrating sound suddenly came from outside his ears, and he was also slightly startled.

The sound seemed to come from inside the well, although the vibration sound was not loud, but it was very clear to the ears of the soldier, and after a moment of slight stunned, the soldier immediately came back to his senses and said in disbelief...... Childe, there really seems to be a voice in this. ”

This soldier is just a big old man, where does he know so much, and he doesn't know how the sound is transmitted, and it is also very strange to hear the "buzzing" sound coming from the cowhide.

At this time, Zhao Fan was about to go to the top of the city with Xu Jia and continue to monitor the Hu people's tent in the distance, when he heard the soldier's voice, he was also slightly startled in his heart, and said, "Get out of the way, let me listen." ”

After a while, Zhao Fan also had a touch of surprise and happiness on his face, that's right, there was indeed a vibration on the cowhide, and, feeling the vibration frequency, the Hu people were not only digging tunnels towards Cloud City, but also seemed to be digging very fast, and they were already close to Cloud City.

Zhao Fan didn't expect that the trick he suddenly thought of would come in handy so quickly.

Immediately, Zhao Fan no longer hesitated, and said coldly: "The enemy army is digging tunnels in the northwest towards Yunzhong City, everyone informs the defenders at the head of the city, be ready for battle, but don't startle the snakes, tonight, I will teach this Hu people who dig tunnels, there is no return." ”

Feeling the location of the sound source of the vibration, Zhao Fan pointed to the northwest direction and ordered a group of soldiers with shovels and shovels to dig in the direction where the Hu people had dug up, and the men and horses on both sides dug tunnels in one direction.

However, the essential difference between the two sides is that on the side of Cloud City, the movements of the Hu people have been discovered, and they are digging tunnels to defeat the enemy, while the Hu people are stupid and don't know at all, their plan of action has been known by Zhao Fan and others.

Zhao Fan came to the ground in person, and silently estimated the progress and location of the Hu people's excavation tunnel, while Xu Jia, at the moment, went to find charcoal and chaff and other things according to the method that Zhao Fan just said.

Zhao Fan listened while looking at the surrounding environment, I have to say that the location chosen by the Hu people is very good, this place is remote, and overgrown with weeds, the guards are not tight, if they successfully dig in, then Cloud City will be very dangerous.

Zhang Wu and the others definitely didn't expect that at this critical moment, Zhao Fan suddenly invented the ground listening and successfully overheard their excavation of the tunnel.

If it weren't for Zhao Fan here, maybe the Hu people's method of digging the tunnel this time could really be successfully realized, and because of this, they would have broken through the Cloud City.

"Tell the defenders at the head of the city to be ready for battle, and also, go and find Xu Ying and Xu Xiong, they have great strength, digging tunnels, and agitating bellows, they need to complete it." Zhao Fan commanded.

At this moment, Xu Ying and Xu Xiong were monitoring the movements of the Hu people on the other two city walls, so they didn't find out the situation on Zhao Fan's side, and it wasn't until they arrived that they realized that the Hu people had chosen this way to attack the city.

They knew that the stakes were high, and they immediately followed Zhao Fan's orders and made meticulous preparations.

Seeing that the tunnels in the city had been excavated and formed, Zhao Fan also ordered: "The defenders in the city, prepare rockets and catapults, and wait for my orders." ”

At this time, Xu Jia had already prepared charcoal and chaff, and as time passed, Xu Ying and Xu Xiong and other soldiers had also dug the tunnel quite deep and extended towards the outside of the city.

When passing through the city wall, in order to prevent the city wall from collapsing, Xu Ying, Xu Xiong and others, with the wooden stakes and boulders that had already been prepared, supported the city wall, at this time, the two sides were getting closer and closer, and there was still a distance of more than ten zhang, and they were about to meet.

Zhang Wu outside the city, there was a touch of surprise on his face, for some reason, he always felt that something was wrong, the location they were in now was almost to the city wall of Yunzhong City, but there was no movement, there was silence in Yunzhong City, this silent atmosphere, in this moonless night, seemed a little weird.

"Stop!" At this time, Zhang Wu suddenly let out a low sigh and stopped the Hu soldiers from continuing to dig.

Seeing that Zhang Wu's face was a little wrong, a Hu leader also stepped forward and said, "Lord Zuo Xian, what happened?" ”

Zhang Wu didn't answer, nothing abnormal happened at the moment, but he just felt that something was wrong, and the closer he got to Cloud City, the stronger the bad feeling became.

"It's okay, everyone has been digging for so long, take a rest first, and send a few more people to go out to the tunnel first and inquire about the situation in Cloud City." Zhang Wu was silent for a long time, and he also commanded.

Hearing this, there was also a strange look on the face of the leader of the Hu people, Zhang Wu has always been ruthless, and he treats soldiers extremely harshly, this is the first time he has said this kind of words, so he is also a little strange in his heart.

Although he felt that something seemed wrong with Zhang Wu, the leader of the Hu people still transferred two soldiers according to Zhang Wu's instructions and asked them to go to the vicinity of Cloud City to inquire about the situation.

This tunnel is dug very deep, and the location is remote, Zhang Wu is confident that he will not be discovered by the people of Cloud City, but, for some reason, he just feels wrong, this feeling is very abnormal, but Zhang Wu's surname is cautious, as long as he feels the slightest mistake, he will find out clearly and then act.

Therefore, he immediately ordered the soldiers to stop digging and go to Cloud City to inquire about the situation.

It didn't take long for the two soldiers to run back and say, "Report to Lord Zuo Xian, the defenders of Cloud City are not abnormal, they are still observing our big tent at the head of the city as they did at the beginning, and they have not noticed us. ”

Hearing this, Zhang Wu also breathed a sigh of relief, he was silent for a moment, and waved his hand: "Keep digging!" ”

If there is no abnormal situation, then Zhang Wu can finally rest assured, and it is imperative for them to attack Cloud City, so it is impossible for Zhang Wu to give up such a wonderful siege plan because of this bad premonition.

Although he continued to act, at this time, Zhang Wu kept an eye on it, kept his vigilance very strong, and tried to keep a certain distance from the soldiers digging tunnels in front of him, and once there was anything abnormal, he could also quickly escape.

"Okay, everyone prepare, the Hu people are coming soon." Zhao Fan felt the vibration on the raw cowhide becoming more and more intense, and immediately held his breath, his hands trembling slightly because of nervousness.

After all, this was the first time he had used this method to fight the enemy, so it was inevitable that he would be a little nervous.

With the rapid swing of the shovel, the frequency of the vibration is getting faster and faster, and the intensity of the vibration is getting bigger and bigger.

Sure enough, what appeared in front of Xu Ying and the others was an army of about hundreds of Hu people, who looked at the other group of people who suddenly appeared with a stunned expression, and some of them even showed a look of horror in their eyes, as if they had hit a ghost.

"Shoot the arrows!"

Before they could react, Zhao Fan suddenly gave an order, and Xu Ying and the others shot the arrows that had been prepared long ago like locusts at the Hu army on the opposite side.

Seeing that these Hu people were suppressed, Xu Ying also withdrew from the tunnel according to Zhao Fan's instructions, and then violently agitated the bellows with the charcoal burning in the bellows, and a puff of smoke suddenly poured towards the tunnel.

The Hu people in the tunnel were choked by the smoke and couldn't open their eyes, so they reacted, and immediately turned around and ran hurriedly outside the tunnel. (To be continued.) )