Wu Sangui and Guo Zhuangtu and others on Shanhaiguan could not be allowed to discuss too much, after Qin Ying's persuasion to surrender, the Hongyi artillery of the Jingbei Army under the Guanxia had all been fired, and at the same time, the heavy artillery of the Guanning Army also began to emit bursts of fierce roar.

The Northern Expedition of the Jingbei Army carried a total of 80 Hongyi cannons, ten Hongyi cannons were destroyed when Jiaoshan was lost, and several of them were damaged in the artillery battle during the battle of the North Wing City, so at this time, there were only more than 60 heavy artillery pieces that were constantly roaring under the Guanxia, which was not much more than the number of Hongyi cannons owned by the Guanning Army, but Li Xingzhi never thought that he could use the Hongyi cannons to bombard the thick city wall of Shanhaiguan.

At the head of the city, the cannons of the Jingbei Army and the cannons of the Guanning Army kept flying back and forth, and the sound of the explosion made Guan Ningding, who was hiding at home in the city, tremble.

Half an hour after the artillery battle, Li Xingzhi's general flag behind the Yuan Rong car continued to move forward, which was the signal for the Jingbei Army to launch an attack, and suddenly, the new four towns of the Jingbei Army deployed in the Chinese army began to slowly press towards Shanhaiguan.

Li Xingzhi used the guise of artillery battles and infantry attacks to attract the attention of the defenders in the city.

"Pass on the commander's order, put all armies on alert, and once the Shandong army enters the firing range, give the commander 10,000 artillery shots."

Wu Sangui silently estimated the range of the Jingbei Army under the city with a cold face, and there were 900 artillery pieces of various types in Shanhaiguan, even if dozens of them were lost in the artillery battle, but he believed that with such a firepower configuration, it was impossible for the Shandong Army to break through to the city wall.

Not only Wu Sangui is confident, but Yang Kun, Xie Sixin and others are also convinced that the defense of Shanhaiguan is not a false name of Lang, and Dongyu has entered the customs several times in the past ten years, but he did not dare to cross the thunder pool of Shanhaiguan for half a step, which is the proof.

In the rumbling cannon, Tie Zhan and the excavation team composed of hundreds of miners finally dug all three tunnels to the bottom of Shanhaiguan City.

At the end of the tunnel on the left is led by Tie Zhan himself, facing the wall foundation stacked with layers of triple soil and blue-striped stone, the hoe and shovel used by the excavation team have almost no effect, in response to this situation, Tie Zhan can only send an order to dig down, trying to bypass the wall base about a foot deep, and then fill with gunpowder, of course, Tie Zhan did not forget to pass this military order to his comrades in the other two tunnels.

"Bang Bang...... Qiang Bell ...... Bang ......! ”

Although the roar of the artillery on the head of Shanhaiguan City shook the earth, and although the sound of war drums of the Jingbei Army marching under the city was like a storm crashing on the shore, the sound of shovels digging soil was still heard in the listening urn that was only one wall away from Shanhaiguan.

"It's not good, it's the Shandong army digging tunnels, there is a sound here, you go with me to other areas to have a look, you go and report to the military master."

Chen Daquan was originally an Orion in Guangning, Sun Degong surrendered to the city, when the Donglu slaughtered Guangning, he happened to hunt with more than a dozen peers, and was spared, in order to avenge the blood and revenge, they fled all the way to Ningyuan, and then joined the Guanning Army, with their agile skills over the years, they have also made a lot of meritorious contributions over the years, and became a general banner, Orion hunting is to be deaf and clear, Chen Daquan is naturally no exception, so he was appointed as the leader of the monitoring urn.

"Brother Chen, the little one is going to ask the big handsome."

The city wall is related to his life and death, how dare that Guan Ning sergeant delay, and run to the city wall as soon as he smokes.

"Head, there's that too!"

"There's a sound over the head, too!"

Wu Sangui is cautious, almost every listening urn is sent to be on duty, Chen Daquan shouted, originally because of the sound of cannons and shouting to kill a little distracted soldiers hurriedly leaned their ears to the listening urn to investigate, only a moment to confirm the direction of the Jingbei Army's excavation, Chen Daquan did not dare to slack off, immediately ordered the left and right to plant a red flag as a sign in the direction where the sound came from, and then carefully checked the rest of the listening urns, for fear that if one or two were missed, they would be sneaked into the pass by the Shandong army.

"Hehe, this town has estimated that there must be a trick for Xiao Li Thief to suddenly send troops, you see, this tunnel has dug under our noses, how do you say we should deal with it?"

Wu Sangui glanced at the Shandong army who were clamoring for troops under the pass, and Li Xingyi, who was pretending to be on the Yuan Rong car.

Not afraid of thieves stealing, just afraid of thieves, from the time the Jingbei Army entered the army, he hesitated, I don't know what Li Xingzhi's idea is, now things are finally clear, it turns out that Li Xingzhi is fighting, Ming Xiu plank road, dark Chen Cang's mind, want to use the method of digging tunnels to break the city.

"The military master, Xiao Li thief dug the tunnel, its intention is to use gunpowder blasting method, or to ambush soldiers and horses in the tunnel, sneak attack at night, my Shanhaiguan is solid, just the wall base has two zhang because, the city wall is tamped and stacked with Sanhe soil, and the outer bread is covered with green stones and city bricks, and the end will think that the blasting method has no effect on our city wall, and the biggest possibility is to sneak attack at night,"

Wu Zhimao, the deputy general of the Chinese army, was a general of Guanning, and after hearing that the Jingbei army was digging tunnels, he quickly made his own judgment.

Zhang Guozhu laughed and said: "What Vice Marshal Wu said is reasonable, let's set up an ambush at the entrance of the tunnel, if the Shandong army comes out, let's kill one, and when two come out, let's kill a pair, we will see what the Shandong army is capable of!" ”

"The military master, what Vice Marshal Wu said is reasonable, but the deployment of troops to set up ambushes is biased, since ancient times, the method of breaking the tunnel, nothing more than flooding, smoke, the end of the general to see the small Li thief camp is at least five miles away from the city, now the weather is cold, although it is not a drop of water into ice, but the land has long been frozen as hard as iron stone, want to come to this tunnel to break the city, the Shandong army began to implement when the soldiers came to the city, otherwise it is impossible to dig under the city so quickly, the students think that since the little Li thief is playing the method of breaking the city through the tunnel, it naturally has its intentions, so we have to guard against it."

Guo Zhuangtu had a cautious personality, and although he also believed that it was impossible to blow down the city wall by gunpowder blasting, he still euphemistically proposed the strategy of using smoke and flooding in the spirit of being cautious.

"Hmm...... Mr. Guo is reasonable, there is no harm in being cautious, Zhang Guerrilla, Ben Shuai will lead you to lead people along the direction of the tunnel dug by the Shandong army, and also dig a section of the tunnel, and then pour water and smoke on Ben Shuai. ”

Wu Sangui glanced at Guo Zhuangtu approvingly, and felt that this person's personality was similar to his own, and he was cautious, and it was really not a bad thing to marry his daughter to him.

"The last general commands."

Although Zhang Guozhu was a little disdainful of Guo Zhuangtu's strategy, Wu Sangui issued a military order, and he did not dare to disobey it, so he waved his hand and hurriedly went down the city with his left and right guards.

As a result, the Guanning army in the city also followed the example of the Jingbei army and began to dig down the base of the wall.

"Bang Bang...... Bang ......! ”

"Head, there is a voice on the other side, it seems that Guan Ningjun has discovered our actions, what should we do now?"

Under the foundation of the wall, several Jingbei troops who had already excavated the area where the coffin was buried also noticed the sound of digging soil from the opposite side, and hurriedly asked Tie Zhan and other generals in charge of the excavation task for instructions.