Yunyang City is not big. It has been broken by the army many times during more than ten years of war. There are many obvious dividing lines on the city walls. The walls on both sides of these boundaries have different degrees of new and old degrees and colors. Every time they are captured, the city walls will be seriously damaged. If the occupier unintentionally defends, he will abandon them. If he intends to defend, he will patch the city walls. Due to frequent wars, new patches are constantly needed, and patches may be patched. Sometimes, Yunyang changes hands again before even finishing the repair work.

So the Yunyang city wall in front of me is like a patchwork robes of a beggar. On the vast land of the lake, all armies come and go, and many cities have experiences similar to those of Yunyang. The city has changed hands many times, and the city walls have been repaired.

Yunyang is a small city with four standard city gates. You can imagine that there are about two relatively wide roads inside, each connecting two city gates and crossing in the center of the city. The intersection will be where the yamen in Yunyang City are located. The four city gates do not have the urn city structure like the tall Kunming City, but simply built a simple city tower to enhance the defense capabilities of the city gate.

Although it is not clear about the specific strength of the Qing army in the city, Yuan Zongdi and Liu Tichun probably would have three or four thousand people. The strength of the Ming army was not strong enough to block all the four city gates, so the Ming army only set up camp outside the city gate in the south, concentrated the soldiers here to threaten the city, and launched an attack on Yunyang to train the soldiers. In addition, half of the auxiliary soldiers were drawn, and a small number of soldiers were protected to collect supplies in the suburbs.

The Ming army's work of collecting materials and moving the population gave Deng Ming the feeling that he was close to the bandits, but he could not interfere and had no way to stop it. When the Ming army was having a difficult life, it was impossible to expect them to use gentle means to persuade the people to voluntarily go to the Three Gorges to go to the Three Gorges with them. If Deng Ming himself was an ordinary citizen, he would not want to be a serf in the Three Gorges and reclaim military camps.

There was no moat outside Yunyang City, only a not-so-wide trench. Yuan Zongdi and others saved the training process of digging canals and digging water, and directly began to guide their subordinates how to efficiently fill the trench, destroy the fortifications beside the wall, and build siege equipment.

Outside the Yunyang city wall, there are many wooden stakes that were nailed into the ground. Deng Ming had seen them before in front of Chongqing City and knew that these wooden stakes were called "Plum Blossom Pile". The defender arranged such things in a staggered manner to hinder the enemy's ladders, and the carts were close to the city wall. Like the Yunyang city wall, these wooden stakes on the ground were also new and old. Some of them were almost decayed and did not play the defensive role they should have; while some were brand new and did not look like they were nailed into the ground for a long time.

"The time for these wooden stakes to be nailed into the ground is obviously different," seized an opportunity, Deng Ming pointed to the plum blossom stakes with new and old stakes and asked Liu Tichun: "It seems that they are far behind for many years, right?"

"Mr. Deng said it well." Although Liu Tichun did not come to Yunyang often, he could clearly see the situation here. He told Deng Ming that Hao Yaoqi had come to attack Yunyang many times. If he hadn't come for a while, he would definitely go to Gucheng. Whether in Yunyang or under Gucheng City, Hao Yaoqi was the first to Liu Tichun and Yuan Zong. He did not forget to use the opportunity to go out to train his soldiers, and each time he would cause some damage to the plum blossom stake position in front of the city.

After the Ming army left, the Qing army would inspect the plum blossom piles under the city and fill in the gap destroyed by Hao Yaoqi, so the wooden piles would be new and old. The Qing army was too lazy to dig out and replace those old and decadent wooden piles because they were used to Hao Yaoqi's usual style and knew that the other party would not force the attack on the city.

Deng Ming saw that when the Ming army was conducting siege drills, the Qing army on the city was also conducting defensive drills. When the Ming army destroyed the fortifications, the Qing army on the top of the city used firearms and bows and arrows to interfere. However, the Ming army did not really want to siege the city, so they paid great attention to protecting the soldiers, and would not take risks for destroying the fortifications, so the formation arrangement was very loose. Similarly, the defenders did not really want to kill the Ming army, and the main purpose was to train new recruits, so the harassed shooting of the Qing army was of little effect. The siege lasted for two days, and the Ming army only cut off more than a dozen stakes and paid the price of injury to several people.

Since the time of Li Zicheng, the rebel army attached great importance to siege technology. Liu Tichun and Yuan Zong, the second person, moved to the world as the Eighteen Cavalry of Shangluo, attached great importance to these technologies. They pulled out wooden stakes in front of the city and built ladders behind the camp. Although they did not intend to really siege the city, the entire Ming army camp was busy.

Not far from the city wall, the Ming army quickly piled up a mound.

"This is a must-have before the attack begins," Liu Tichun led Deng Ming to check the mound. After the Ming army piled up the mound, they quickly began to dig the tunnel: "The mound cannot be too far from the city wall, otherwise the tunnel will stretch too long, making it difficult and time-consuming to dig, and the possibility of failure will be greatly increased."

When digging tunnels, you need to consider ventilation. The longer the tunnel, the worse the breathability, and you need to dig it wider. Therefore, Liu Tichun believes that the closer the tunnel is to the city wall, the better. The construction of the mound is to cover the excavators working below, and the more effective defense method of the defenders is to send people out of the city to attack the mound and block the entrance.

"According to the fact that the defenders of Yunyang will not come out to attack this mound, but we must beware. If they attack, the boy below will be buried alive."

Liu Tichun told Deng Ming that it is also a knowledge to defend against the enemy's sneak attack on the earth mound. Because the earth mound is close to the city wall, it is easy for the defenders to observe the deployment of the attackers around the earth mound, and they will be more targeted when launching a counterattack. Of course, if the troops are rich and time is sufficient, and the attacker can dig the tunnel very wide, the earth mound may also move a position backward to a safer distance.

This mound of the Ming army was located in the middle of two city gates, at the corner of the city wall. In this way, no matter which city gate the Qing army came out, it had to go a long way to reach the entrance of the tunnel. The position of the hang corner also gave the Qing army the least shooting position and observation position. If the Qing army assault team planned to go down the city, it would be more difficult and easy to be discovered by the Ming army. Liu Tichun and Yuan Zongdi deployed defensive troops around the mound, and in order to facilitate the concealment of the defensive troops, they also dug some traffic trenches. At the same time, rotating guard troops were deployed in the rear, so that they could forward reinforcements at any time.

Deng Ming looked at the well-organized deployment and knew that these were the lessons learned by the camp in the past twenty years. He didn't know how many soldiers' lives had been paid for it. Compared to chopping wooden stakes by the wall, digging tunnels was safer, and it was more in line with Liu Tichun and his ideas of training soldiers while avoiding casualties. The main force of the camp in the camp was on the side of the mound, and officers from each team took turns to go to the tunnel to observe on the spot. Liu Tichun and Yuan Zong, the second person, explained to the young officers repeatedly.

Other officers just used their brains to remember, while Deng Ming recorded them all in detail in his notebook. Deng Ming also asked about previous battle examples and asked what kind of experiences and losses caused the camp to have the idea of ​​making these arrangements.

"There are no other two purposes of acupuncture. One is to dig tunnels into the city, and the other is to destroy the city wall. It is very difficult to attack the city from the tunnel. The tunnel must be very wide and can accommodate a large number of soldiers to enter the city quickly. If this is the purpose, you cannot pile up mounds at the corner of the city wall, otherwise the defense party can only build an inner wall at the corner of the city inside, and it does not have to be very wide, and you can completely block the way."

Liu Tichun introduced his past experience to Deng Ming, while Yuan Zongdi explained the war examples while listening, while Deng Ming was busy recording.

Those who attempt to attack the tunnel and enter the city will choose to build a mound on the front of the city wall, which will be closer to the city gate. Because even if you successfully drill into the city from the tunnel, only one tunnel still cannot guarantee that the army will pass quickly. The purpose of the cave to attack the city is to cooperate with the frontal siege troops to seize and open a city gate.

When digging tunnels around the corner of the city wall, the experienced guards knew at a glance that the attacker's intention was to dig the foundation of the city wall. After digging to the corner of the wall, the attacker did not dig through the city wall, but continued to dig deeper. At the same time, he moved some solid wooden piles into the tunnel. After transporting the soil below the wall foundation, he used these wooden piles to support the wall foundation. After completely hollowing out a section of the city wall, he evacuated personnel and set fire to the wooden piles supporting the wall foundation, causing the wall to collapse.

"The key is ventilation. If the tunnel is too narrow and not ventilated, it will not be able to burn the wooden stakes." Liu Tichun believes that in the face of this kind of attack of poaching, the best defense is still to take the initiative to attack and destroy the entrance of the tunnel. When facing this attack, the ventilation methods of the tunnel are also related to the lives of the soldiers below: "It takes a long time to dig the tunnel. If the wall is hollowed out, it is impossible to install enough wooden stakes without ten days and half a month. If the city wall is thick, more wooden stakes are needed and the excavation time will be longer. In order to burn more wooden stakes, it is necessary to dig the tunnel wider. During this period, it may be attacked by the enemy from the city. As long as the enemy successfully breaks through to the entrance of the tunnel, as long as they control the entrance of the tunnel for a quarter of an hour, or even a stick of incense, they can seal the entrance with soil capsules, and those who are still inside will be suffocated to death."

"The most important thing about acupuncture is not how fast it is to dig, but how to protect the mound." Yuan Zongdi deeply understood this. In his past military career, especially when the camp was still lacking in experience in siege in the Chongzhen period, the camp attacks would always fail because the soldiers defending the city attacked the mound. Even if reinforcements rushed to drive out the enemy, they could not dig out all the soil bags blocked at the entrance of the cave for a while. When the entrance of the cave was opened again, there were no living people inside.

"Later, we would have prepared a large number of bamboo poles before we started digging tunnels." This time, Yuan Zongdi and Liu Tichun also prepared many long thick bamboo poles, opening them all, and inserting many bamboo poles into the ground when digging tunnels: "Sometimes, even if you are careful in defense, you will still be attacked by the dead soldiers sent by the enemy to the edge of the mound and seal the hole. At that time, these breathable thick bamboo poles can save lives and allow the people below to persevere until we dig out the soil bag. When the task is completed, when the wooden stakes supporting the wall foundation are to be burned, these bamboo poles will breathe and make the fire burn longer."

"Will this not reveal the direction of the tunnel?" Deng Ming asked in confusion: "Besides, what should I do if the enemy blocks the bamboo pole when blocking the hole?"

"It is possible to guess the general direction of the tunnel to the city, so it is much easier for us to insert some fake bamboo poles on the ground to confuse them. It is much easier to insert some bamboo randomly than digging tunnels. We will not give the enemy a lot of time, so how can they block the hole and cut bamboo?" Yuan Zongdi pointed out that if such a thing happened, it only means that the attacker has completely lost control of the ground. If the army on the ground is defeated, then the people underground will die.

Deploying defense and inserting real and fake ventilated bamboo poles. Yuan Zongdi and Liu Tichun were both very attentive to do these things. Yuntu and the others personally taught each other. But they did not really want to hollow out the foundation of Yunyang, because this was definitely not something that could be done in the short term. The city had both proactive response methods and many passive defense methods. For example, building new inner walls in the city to pre-block those gaps caused by the collapse of the city wall; or digging a canal inside the wall and pouring water into it when the attacker was preparing to burn the pillars. No matter which method of response, it would take manpower and time, but it would still be less than the workload of hollowing out the foundation of the wall. Yuan Zongdi and Liu Tichun could not predict what measures would be taken in the city. Going out of the city to counterattack and pouring water to the tunnel could cause great losses to the attacker.

After the local road was dug under the foundation of Yunyang wall, Liu Tichun and Yuan Zongdi planned to finish the work.

Now the excavators can personally experience the solidity of the wall foundation on the tunnel, and learn how to judge the surface position at the end of the tunnel, achieving all training purposes. There is no need to broaden and place wooden piles later - because the project volume is huge and takes a long time. As for how to place wooden piles in the tunnel, you can practice in other areas, and there is no need to actually go to the wall foundation for drilling.

During this period, Liu Tichun and Yuan Zongdi piled up mounds elsewhere, intending to dig a few more tunnels to let their subordinates train their skills while the iron is hot. The soldiers who collected food and population around him have not yet returned. Hao Yaoqi from Gucheng also sent someone to deliver a letter saying that he had just started sweeping and needed the Ming army in Yunyang to help him restrain him for a while.

However, at this time Deng Ming stood up to express his opinion.

Deng Ming had been learning humbly before and had never questioned any decisions of Yuan Zongdi and Liu Tichun. Now the tunnel has reached the base of the wall. Although it is only a few meters wide and only one meter high, as a modern person, Deng Ming does not understand why he doesn't use gunpowder to blow it up.

"Use gunpowder to explode the city?" Yuan Zongdi and Liu Tichun shook their heads together: "Gunpowder cannot explode the city."

"Why?" Deng Ming felt that this statement violated what he knew.

In this era, there is really no common sense of using gunpowder to blast city walls. Not only does it not have, but there are examples of failure, which Yuan Zongdi and Liu Tichun have witnessed with their own eyes.

"When the second attack opened the seal..."

Since Deng Ming asked, Liu Tichun talked about the past. When the second attack was opened, Li Zicheng had hundreds of cannons in his hand and handed them to Liu Zongmin to attack the city wall. Liu Zongmin used these cannons to blast Kaifeng City day and night for several days, but still failed to blow the city wall out of the gap, and there was no sign of the gap - because the caliber of the guns seized by Li Zicheng was too small and had no ability to attack the city.

In desperation, Liu Zongmin continued to increase the charge, and a large number of chamber explosion accidents occurred. Not only did he still have no choice but to the Kaifeng city wall, but he caused great casualties to his own people and lost a lot of artillery. However, the chamber explosion reminded Liu Zongmin. He had a sudden inspiration and ordered the drilling of a hole in the Kaifeng city wall and then filled in a large amount of gunpowder.

Yuan Zongdi remembered that Liu Zongmin's original words back then were: "Let the Kaifeng city wall explode like a cannon."

And what's the result?

The result was that after the gunpowder was lit, the big hole filled with gunpowder on the Kaifeng city wall set off fireworks. The very spectacular and beautiful fireworks were seen clearly by the crusades within a radius. After the fireworks were set off, what should the city wall be like? Liu Zongmin sacrificed a huge sacrifice. The hole he dug with great effort turned out to be as big as he is now.

"Gunpowder cannot attack the city. You must first cast cannons, a heavy cannon of thousands of kilograms, and then use cannons to blast the city wall. If you encounter a thicker city wall, you need a heavy cannon." This is what Yuan Zongdi and Liu Tichun think. They do not have the ability to cast such cannons, so they do not have the ability to attack the city.

"Then why cannons explode?" The statement that black gunpowder cannot be used to explode is the most ridiculous military view that Deng Ming has ever heard of, and he immediately asked back.

Yuan Zongdi said he didn't know about this, and Liu Tichun believed that this was of course because "fire can overcome metal", and the walls belong to earth and cannot be conquered by gunpowder.

"When we were in Kunming, there was an explosion after we lit the gunpowder depot. Isn't the walls of the warehouse earth? Wasn't they also defeated by fire?"

Liu Tichun said that he was not proficient in the five elements of generation and restraint, so he could not answer such profound questions. But he pointed out that perhaps the word "Ming" in Kunming belongs to fire, which increases the power of gunpowder.

Inspired by this, Yuan Zongdi believed that it should be because Zhu Ming belonged to Fire De. There was nothing strange about the power of gunpowder doubled around the Third Prince, King Fire De.

Recalling his junior high school chemistry knowledge, Deng Ming knew that black gunpowder will produce a large amount of carbon dioxide and nitrogen after reaction. The volume of the gas is nearly 1,000 times the original volume. Gas of more than 1,000 degrees can generate extremely high air pressure in a confined space. If the container cannot withstand pressure in a confined space, an explosion will occur. Recalling the fireworks and firecrackers I have seen in the past, if there is a gap in the packaging, a firework will occur, and firecrackers without releasing air pressure will explode.

"Black gunpowder can explode, as long as..." After some thought and association, Deng Ming became more confident when he spoke again.

Liu Zongmin's failure was just because he didn't understand junior high school chemistry and did not create a confined space.

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