After discussing with Ju Zhu, Zhuge Liang quickly asked Liu Bei for instructions, filed his ideas, and then conveyed them to Gao Shun.

Let Gao Shun's troops Liao Hua and Zong Yu lead the soldiers in the army who are good at earthwork to dig up and build offensive fortifications that repel Guo Jia's elastic defense line.

Fortunately, last fall, Pang Tong tested the Z-shaped trench for the first time in the Youzhou battlefield and also reported some data that Zhuge Liang could run-in and optimize again.

The enemy has never seen such things before, and the information difference between the two sides is very obvious, so the user will naturally become more and more adept.

Of course, when Pang Tong dug the Z-shaped trench last fall, he mainly covered the crossbowman and did not involve the deployment of the catapult.

But the principles of the two are the same, especially the ballistic trajectory of the catapult is even higher. Even if the catapult is hidden lower, dig a hole on the ground and deploy it in.

As long as there are ground on all sides, the sunken fortifications will be difficult to be targeted by the defenders' catapults.

In particular, Zhuge Liang did not intend to let the stone throwers deployed in front of him load a single-headed bullet. He just needed to hit the wall with a single-headed bullet in the rear row, and to throw grape bullets in the front row.

In the first two or three days of construction, the excavation was progressing very smoothly because the Cao army on the opposite side could not understand what the Han army was doing.

The Han army was digging tunnels, and they began to dig and advance from at least three hundred steps away from the Cao army's position.

Even Cao's army did not notice at the beginning that the Han army's trenches were moving forward in a tortuous manner, or even if the eyes saw it, because the mathematical and geometric knowledge in their minds could not keep up, the brain could not react. "What are the benefits of digging the trenches into tortuous conditions."

It’s not that ordinary soldiers couldn’t react, but that Guo Jia, who was patrolling the defense line every day, did not react, and Cao Cao in Yancheng City behind him naturally didn’t understand it even more.

After digging for a while, Cao Jun noticed that the Han army was not digging authentic tunnels, but just trenches, because they were not potentially underground, but had the top open. But even after paying attention to this supplementary information, they did not understand.

There is no way, it has nothing to do with intelligence. I can only say that if you don’t understand mathematics, you don’t understand it. No matter how scheming and calculating people have never learned it, you don’t understand it.

The Cao army generally felt that there was no problem. At most, based on the general general tactics of defense tunnel warfare, they arranged to dig deep into the long trench behind their first line of defense to deal with it.

That is, like the Battle of Guandu six years ago, they are all old tricks that have been used.

The speed of excavation work is not slow. Traffic trenches can be dug within about three to five days, and then it is time to dig the side trenches where the firepower points are deployed horizontally.

Who made Zhuge Liang have an engineering army that had been digging for three years? They dug through the Nanyang Canal, blew through Tongbai Mountain, and built the new urban defense system of Kunyang City.

This team is the best team in China today who is good at opening map editors. The Hebei Army, which once known as the best in the world in the cave, can only be at a disadvantage compared to the strength of digging ditches.

It can be said that the excavation technology is better? The great Han Dynasty looked for Nanyang in Jingzhou.

...

However, Zhuge Liang also considered that Guo Jia on the other side was suspicious after all. If he just digs the trenches and makes other tentative advances at the same time, it would be difficult to conceal his true purpose.

Therefore, while the Han army was constructing, it was inevitable to fight head-on battles every day. It used the firepower of the catapults originally deployed to prepare to smash the enemy's first line of defense, smashing more broken gaps, and the crossbows on both sides were consumed.

Anyway, both sides would burn supplies for this kind of counterattack, and the Han army was definitely enough. Cao Cao could not imagine the wealth of Jingzhou and Yizhou. The continuous war materials were transported from the Nanyang Canal. Liu Bei could fight any war of attrition.

In the first few days, Cao's army insisted on deploying crossbowmen behind the defense wall, thinking that they were surveillance, and fearing that the Han army would use tricks and pretend to dig tunnels to actually launch other sneak attacks.

However, because the range of Cao's crossbows is nearly fifty to one hundred steps than that of the Divine Arm crossbow, the Han army's crossbowmen can output outside the range.

Although Cao's army had bunkers and the crossbowmen were not seriously injured, it was too harmful to be killed by the enemy in vain when flying kites outside the range.

After persisting for a few days, Cao's army found that there was no sign of charge and attack, so they gradually reduced the number of crossbowmen on the wall.

Guo Jia also knew that being beaten was not a solution like this. If he wanted to find a way to boost morale occasionally, he thought of deploying the catapult in front of him and bombarding the Han army's god-arm crossbowman with gravel grape bombs.

Even if the catapult uses gravel, the range is much further than that of ordinary crossbows, and it can reach the Han army's god-arm crossbowman.

Moreover, the Han army's god-arm crossbowmen have helmets and breastplate. After the distance is far, even if the Cao army's crossbow arrows are shot, it will be difficult to penetrate armor, and the killing efficiency is extremely low. I can only count on the grapes of the catapult.

On April 19th, Cao's army used gravel rain to knock on the Han army's crossbowman formation for the first time. The Han army caught off guard and actually suffered some casualties.

But the Han army immediately adjusted its tactics. The next day, Zhuge Liang asked the Han army to arrange a catapult to counterattack, and at the same time, let the Divine Arm Crossbowman use a more scattered formation to prevent multiple soldiers from being covered by gravel rain.

The Han army's catapult car not only has good quality and has a longer range, but also has good training in the soldiers. Zhuge Liang provided them with a set of ballistic tables with corresponding values ​​of trigonometric functions. The distance and left and right should be adjusted more quickly, and feedback can be calibrated according to the bounce point.

Although Cao Jun also relied on his simple experience to know how to roughly adjust the shooting direction of the catapult, such as reducing the counterweight when shooting far away, adding the counterweight when shooting close, and also knowing how to adjust the left and right, the feedback speed and calibration efficiency of this adjustment are much lower than that of the Han Army.

One is holding a ballistic table, and the other is just a mental arithmetic estimation.

Moreover, Zhuge Liang did not forget to build a high-level tower at least four hundred steps away from the front line in the battlefield these days, and then let the confidant officer with a strong look and voice go up to the tower to be an artillery observer.

Use a telescope to observe the position of the catapult hidden behind the defense wall, observe the deviation of the landing point of the stone on one side, use a paper tube horn to roar to the messengers under the watchtower, and then command the catapults to adjust.

With such a system, Cao Jun's catapult car wanted to play against the Han army, but he was no match for him at all.

Within two days, the Cao army deployed more than fifty catapults behind the long wall of the first line of defense. Such a terrifying loss speed made Guo Jia quickly give up on the bombing and reported the harsh situation on the front line to Cao Cao in the city, begging for further guidance and decision.

After Cao's front-line positions were scattered, Zhuge Liang's trench operations were basically completed.

It was April 24th. Before dawn, the Han army quietly deployed dozens of catapults and two thousand crossbowmen in a horizontal trench fifty to one hundred steps away from the first wall of the enemy.

The main reason is that the horizontal length of the trench is still not enough, so there are only so many people who can stand first.

Of course, Zhuge Liang would not see the only two thousand crossbowmen exposed to the blade of the enemy's melee troops counterattack. The Han army still had a large number of melee troops that could be blocked at any time.

If the Cao army really had the courage to let the cavalry break out of the defense line and fight from a high place to close and crush the divine arm crossbowmen in the trench, the Han army would just want to fight a field battle.

After dawn, the Han army began to launch an attack, and Zhuge Liang was very sinister. Until now, he did not intend to expose the firepower in the trench ahead, so as not to let the enemy realize that "the soldiers deployed in this sudden trench can kill and injure the soldiers on the first and second lines of defense of Cao's army at the same time."

After all, if the enemy is alert, the effect of sneak attack when suddenly taking action will decrease.

Therefore, Zhuge Liang still only mobilized the catapult and crossbowmen at least two or three hundred steps away from the enemy.

After about a cup of tea, the two Han army camps and thousands of infantry equipped with steel cone guns began to charge towards the defense line.

After several days of firepower preparations, the gap in the defense line was several times higher than the initial feint attack. This was the premise that Cao's army used simple rammed earth to repair the smashed gap every night. If Cao's army did not repair it, it would probably be that half of the walls of this defense line would no longer exist.

The Cao army on the opposite side was also ready to fight according to tactical arrangements. When the Han army's firepower was crazily covering the first wall, they temporarily retreated to find cover. The Han army's melee soldiers came up and they were re-entered.

Guo Jia, a military advisor who observed the battle behind the second line of defense, and Le Jin, who was responsible for the specific defensive command, were very rigorous in the implementation of the plan, but for some reason, they always felt nervous.

After all, Gao Shun had failed to test the attack a few days ago. Now he has prepared fortifications for a few days, but he still used the old method to do it again. What is this? Is it because Liu Bei is connected? He is not stingy with human life and is just consuming minced meat with you?

Fortunately, as the melee battles became more and more intense, Zhuge Liang quickly made Guo Jia and Le Jin no longer have to be anxious.

The second floor-standing leather shoes are better than never falling down.

While all the soldiers on the second line of defense of Cao's army flocked forward and threw themselves in, the Han army's catapults in the front trenches calculated the range and fired gravel rain with high throwing ballistics. Two thousand god-arm crossbowmen also shot and covered the back of the gap.

The Cao army's melee troops, which were charging in the open area between the two lines of defense, were hit hard when they were marching without any cover. Because the crowd was quite dense, they were tragic in an instant. Hundreds of soldiers fell to the ground and wailed, or were trampled on by the soldiers behind them.

In the rear of the Han army, the large crossbowmen troops, nearly 300 steps from the front line of defense, also began to advance, trying to seize the wall of the first line of defense.

"The crossbowman shoots with all his might! Squeeze the crossbowman of Gao Shun's divine arm! The catapult cart hits the first wall!" Guo Jia, opposite, also realized that something was wrong, and couldn't help but come out personally to direct Le Jin to perform tactical actions, which shows that he was also anxious.

Originally, Guo Jia was just talking about it, so how could he do these micro-jobs such as "the crossbowman advances fifty steps and the catapult cart smashes a wall"?

Le Jin didn't mind. He continued to execute the tactics resolutely and calmly, but unfortunately he found that the expected effect of the same trick was very different from ten days ago.

The Han army's crossbowmen could not suppress them, and even the Cao army ventured to block the door with the two armies' fierce fighting. Regardless of the enemy and us, the Han army still had at least thousands of strong crossbows in the back row of the Cao army's reserve team.

The open area between the two lines of defense became a meat grinder that kept Cao's army losing blood.

And this time, Gao Shun seemed to have truly shown his willpower level - he took a feint attack ten days ago and withdrew. It was not that Gao Shun could not afford to die and dared not fight tough battles, he was just testing the reality and reality. When he was really sure of the general attack, Gao Shun was more determined than anyone else in the battle.

The Han army did not seem to be anxious at all, and just consumed it calmly and repeatedly tug-of-war, but it seemed extremely resilient.

Cao's army finally couldn't hold on. After spending more than half an hour on blood circulation, Le Jin's troops could no longer be restrained, and the back-row reserve team did not have the courage to invest in time.

Guo Jia realized the problem. If he ordered the troops to fight back at this time, he would probably collapse ten miles in the moment when he couldn't hold on and completely throw away the defense line from Rushui to Lishui outside the city.

"Give up the first line of defense and put the reserve team in the second... No! The third line, re-deploy the deployment! Let the blocking troops retreat!" Guo Jia judged the situation and still let Le Jin retreat very decisively.

Cao's army quickly retreated like a tide, and most of them were still in order. Only the troops behind the palace were slaughtered and crushed, and nearly two thousand corpses were left behind. These people were all for the withdrawal of friendly troops to get time to fight and block.
Chapter completed!