The Qin army stopped at Bucheng south of Chencheng.
This is because Bucheng is the intersection of Bianshui River and Yinghe River. If waterways are to be used for shipping, the intersection of the two rivers must be a battleground for military strategists, because it can control both rivers at the same time.
The other is that Bucheng is exactly fifty miles away from Chencheng.
The distance of fifty miles can be covered by infantry in one day's march, so it is equivalent to having Chen City at your back.
As mentioned before, Chencheng's defense is a dead city and is actually not suitable for defense.
The same goes for cities with moats, such as Daliang. Although this type of city is easy to defend and difficult to attack, it is extremely easy to be trapped and difficult to launch a counterattack.
In ancient times, most cities required "advance, attack, retreat and defense", that is, no moat. If they wanted to counterattack, soldiers could leave the city and set up formations under the cover of the crossbow range of the city wall.
This is the wall that armies and soldiers really need.
On the contrary, in dead cities like Daliang and Chencheng, the army cannot enter the city to set up defenses and can only station outside the city to fight the enemy. The outcome is actually decided outside the city. Ordinary soldiers have almost no use for the defensive facilities of the city wall.
In the final analysis, this kind of extremely defensive city wall is just a psychological comfort for the princes and nobles to save their lives. Only a foolish king like King Wei would gather all his troops and defend the city.
Of course, it was impossible for the Qin army to deploy its troops in Chen City at this time.
If this is the case, the Chu army only needs to place thousands of crossbowmen or trebuchets at the exits of each city gate to block the paths out of the city... and can easily seal hundreds of thousands of Qin troops in the city.
This arrangement of the Qin army reassured Xiang Yan.
Because he believed that the Qin army at this time must maintain a defensive posture due to insufficient food and grass, and left Chencheng in order to launch another attack during the next year's grain harvest.
So when Xiang Yan followed the Qin army to the port city, he issued an order to the Chu army to build fortifications.
Xiang Yan said to the map on the case:
"We must build three fortifications before next year's harvest."
Xiang Bo was a little confused:
"Why build three fortifications?"
Xiang Yan pointed to the map and explained:
"The Qin army will definitely attack Chu again during the harvest season next year."
"And this place is four hundred miles away from Ruyin. For every hundred miles, one fortification requires three."
"At that time, our army can use the fortifications to fight the Qin army, fight and return all the way back to Ru River, so that the Chu country will be safe!"
The generals nodded in agreement.
It is well known that the Chu army's combat effectiveness was not as good as Qin's.
For example, this time, Xiang Liang's sneak attack on Liang's army in Chencheng failed and he lost tens of thousands of troops, and then Xiang Luo's cavalry army was defeated, forcing Xiang Yan's army to withdraw to defend the city.
Therefore, if the Chu army wants to fight the Qin army in the wild, it must rely on fortifications to occupy the favorable terrain.
Just like Xiang Yan said, every hundred miles of fortifications can be used to cover each other's retreat. By the time the Qin army reaches the Rushui defense line, it will be exhausted and become a tired army... Then it will be like now.
We can only withdraw our troops.
Some ministers even suggested:
"My subordinates believe that one fortification every hundred miles is not enough to resist Qin, and one should be built every fifty miles."
"Because the infantry marches fifty miles a day, and if it marches a hundred miles, there will be no fortifications available overnight, and they may be besieged by the Qin army."
Xiang Yan explained:
"If the fifty-mile joint operation is carried out, I am afraid that it will exceed the capabilities of our army and cannot be completed within a few months."
"Therefore, city fortifications can be set up within a hundred miles, and wooden fortifications can be set up at fifty miles."
So the generals were speechless.
The city fortifications were made of earthen walls to prevent trebuchet attacks, while the wooden fortifications were simple fortifications used to temporarily resist the enemy.
The fortifications Xiang Yan built in Bucheng were quite special. He planned to build a wooden village first and then build a city.
The reason is that it takes more time to build cities. If the Qin army suddenly launches a counterattack, Xiang Yan is worried that the Chu army will not be able to resist without fortifications.
Then, in order to strengthen the defense in the Bucheng area and build follow-up fortifications, Xiang Yan almost evacuated the troops and labor on the Ru River line...
This approach is obviously wrong for modern warfare.
Because in modern times, you only need to use helicopters and transport planes to airdrop a group of troops to Ru River and capture the Chu army.
But there were no helicopters at this time, and the transport aircraft could not conduct three-dimensional operations.
So Xiang Yan can do this with confidence. Anyway, the main force of the Qin army is in Chencheng. As soon as the Qin army attacks the Chu army, it will retreat step by step. It will always retreat to Ru River and stabilize its position.
On the basis of this strategy, there is nothing wrong with building more fortifications on the front line if it can cause the Qin army more trouble and regain more lost ground.
And this is exactly what Shen Bing hopes.
Information came from Chu State like snowflakes.
This intelligence network was set up in Chu territory by Yang Duanhe when he withdrew his troops.
It is not easy to say that intelligence in this era is easy because reconnaissance methods are relatively backward.
It is not difficult to say that it is difficult, because the anti-reconnaissance methods are also backward.
But if you just want to know how many troops the enemy has transferred to the front line or how many troops are left in the Rushui defense line... these are easily available.
All Yang Duanhe had to do was to let some soldiers pretend to be Chu people on the spot, then distribute some dry food and carrier pigeons to hide in the dense forests on both sides of the road, and watch down the mountain all day long.
Yang Duanhe looked at the information and compared it with the map:
"The Chu army has assembled more than 300,000 troops in the port city."
"Another 100,000 troops were deployed on the Taocheng and Lincheng lines, and a large number of laborers were recruited to build defenses on these two lines."
"Only a small number of troops are left to garrison the Ru River line. Among them, there are more than 5,000 men in Chengfu and Ruyin cities each."
Shen Bing nodded.
This is exactly what he wanted to see.
The ancients of this era were often like this. When fighting a war, they would build fortifications or city walls, so a large number of Great Walls appeared between countries.
In order to defend against the Xiongnu, Ying Zheng connected these Great Walls together.
If this project were put into modern times, it would be a proper "Maginot Line", which is a passive and backward absolute defense idea.
But in ancient times, this kind of two-dimensional warfare was really useful. For example, the Great Wall deterred the Huns time and time again.
However, Shen Bing is not from this era, so he certainly knows how to deal with this kind of passive defense.
At this time, a messenger sent a secret letter.
Yang Duanhe opened it and saw that it was sent by Ying Zheng.
After reading it, he frowned slightly and said:
"The king asked about the situation of our army, especially the food and grass."
"How should I reply?"
In order to avoid the leakage of intelligence, for example, Yang Duanhe sent a letter to Ying Zheng, saying that this was a plan carefully arranged by Shen Bing to lure the snake out of the hole...
If something happens to the messenger on the road and he is intercepted by the Chu army or thieves, his success will be in vain.
This situation is very likely to happen, because all the way from Yang Duanhe to Handan are the three realms of Chu, Wei and Zhao. Not long ago, they were all enemies of Qin.
If he gave false information to Ying Zheng, it would be another crime of deceiving the emperor.
So Yang Duanhe simply said nothing.
Now Ying Zheng wrote to inquire, but it was impossible not to reply.