Compared with directly attacking a city with a city, it is still a town with 20,000 soldiers and horses in the city.

Zhou Yu's manpower is simply daydreaming.

Instead, he went to deal with the difficult building, a wild Karasuma royal court, with no defensive equipment around, at most some rejection horses and wooden fences.

Thousands of soldiers and horses have every chance to fight down.

No matter how you look at it, it is much easier to deal with Shan Yu with Karasuma than to attack the castle directly.

"Then it's decided, let's attack that Karasuma Shan Yu first, please Gongsun Baihu, pay close attention to the dynamics of Karasuma Shan Yu in the next few days, be sure to find out the deployment of Karasuma Royal Court forces and some movements of Shan Yu, we are good at fighting for the information we have, and make corresponding deployments."

After receiving Zhou Yu's order, Gongsun Du immediately nodded, clenched his fists, and began to do things according to Zhou Yu's instructions.

The group began to get busy.

And Zhou Yu is fighting, Karasuma Shan Yu's idea, and in Jizhou on the other side, Liu Zheng is also thinking about how to deal with these Xianbei people who came from Youzhou to support.

Rested for two days.

Those Xianbei people who came from Youzhou to support them, combined with the soldiers and horses of Badun, Yuan Xi and others, and came directly to the city of Xindu.

Not only did he surround Liu Zheng in the city of Xindu, but he also ordered his men and horses to start sweeping around Qinghe County, looting grain, grass and materials.

Liu Zheng was afraid of the soldiers and horses of these northern nomads, and did not dare to go out of the city to fight them for a while.

It's not because Liu Zheng is afraid.

It was Liu Zheng that the other soldiers and horses had not yet arrived in Xindu City.

At this time, these enemy troops outside the city did not attack the city.

If you attack rashly, it will not be beneficial to Liu Zheng.

So he had to wait for the time being.

Wait for the army of Wenpin and Zang Ba to come from Yecheng to Xindu.

When the time comes, we will gather our forces and fight these enemy forces to the death.

It's just that the closer he gets to the big war, the more Liu Zheng hates these nomadic people.

I can't help but think about why these nomads always come to attack the Central Plains.

Speaking of which, as a modern person, Liu Zheng still understands these things relatively clearly.

Speaking of which, this is still a problem left over from history.

Since the beginning of the Western Zhou Dynasty, the Central Plains Dynasty has been plagued by nomads, the Western Zhou Dynasty has the dog Rong, the Qin and Han dynasties have the Xiongnu, and then there are Xianbei, Turkic, Rouran, Khitan, Mongolia and so on.

Moreover, in the more than 2,000 years of history of the land of China, nomads basically invaded the Central Plains.

Few Central Plains dynasties took the initiative to send troops against the nomads in the north.

Even if a few dynasties invaded the steppes, it was only for strategic preparation.

And not really to occupy these steppe areas and bring their territory under their own dynastic rule.

Even because of this, a great miracle on the land of China was born, the Great Wall.

Its role is to resist and stop the invasion of the steppe nomads into the Central Plains.

The Great Wall is also the border between the Central Plains Dynasty and the steppe nomads, and within the Great Wall, it is the place where the Central Plains Dynasty can command.

Beyond the Great Wall is the area where the steppe nomads can move.

The geographical location of the Great Wall is related to an important dividing line on the land of China.

It is what I learned in the geography class of junior high school in nine years of compulsory education, and the rainfall line is 400 mm.

This 400 mm rainfall line is very similar to the distribution of the Great Wall.

There is abundant rainfall south of this line, with a lot of rain every year. Abundant rain will be able to meet the needs of agricultural production.

Precipitation is scarce north of this line.

It's hard to survive trying to grow crops.

Some herbaceous and woody plants are difficult to grow.

Only some basic grasses can be grown.

So this area can only be grassland.

At the same time, it is easy to understand why they are so scarce.

These rainfall lines are actually roughly the same as those planned for the Great Wall. It can be seen that the wisdom of the ancients.

In the north of the rainfall line, no grain can be grown, only some wild grasses, and people cannot eat grass for a living, so in order to survive, they can only raise some cattle, sheep and horses that feed on herbaceous plants, which is called animal husbandry.

Then people eat animals, or use animals for commercial trade, so as to achieve the purpose of survival.

Some people may say, how good animal husbandry is, there is meat to eat at meals.

This is much cooler than being whole grains every day.

It seems that there is indeed no problem with this.

But there is a serious problem here.

In this era, there are only some natural grasslands in animal husbandry, and there are no artificial grasslands and grass seeds, and the growth rate and yield of forage required by those livestock cannot meet the standard.

Forage is very limited, in fact, there are not many cattle and sheep.

Even in Liu Zheng's era, the entire Mongolia was only a few tens of millions of sheep.

In the final analysis, it is because forage is also limited.

Tens of millions of sheep sounds like a lot, but if you convert it, if you feed a million people.

One person can only get a few dozen sheep.

Just eating sheep will be eaten in a few months.

Moreover, cattle and sheep are not like agricultural production, and the seeds planted can be harvested once a year, and some can even be harvested several times a year.

It can also be staggered.

The breeding of cattle and sheep is much more complicated than farming.

Therefore, even nomadic people, on average, can't eat sheep a few times a year, that is, like the Central Plains people, they will eat a few meals during the New Year's holidays.

Of course, it must be more than the people of the Central Plains.

Historically, during the period of Emperor Wu of the Han Dynasty, Emperor Wu of the Han Dynasty invaded the Xiongnu in the north, in addition to fighting the Xiongnu army, he would also steal the cattle and sheep of the Xiongnu.

For example, in the Battle of Henan, the Han Dynasty army won a complete victory.

Annihilated thousands of Xiongnu soldiers and horses, but also captured 3,000 people, in fact, the loss of these thousands of men and horses, for the huge Xiongnu, is nothing, after all, the Xiongnu at that time had hundreds of thousands of troops, a few thousand people can only be said to be a drop in the bucket.

But the most terrible thing is that this time in defeat, the cattle and sheep that were snatched by the Han were as many as millions!

The loss of millions of cattle and sheep, but the rations, to recover the loss of millions of cattle and sheep, from production to maturity, it will take not months, but years to recover.

Moreover, cattle and sheep will not only be robbed, but may also suffer from natural disasters.

The north is already cold, and if there is a colder year, a heavy snowstorm, it is very likely that a large number of people will freeze to death.

Therefore, in the north, with pure animal husbandry, nomads are basically in a state of not having enough to eat every day.

Eating meat every day, that's basically impossible.

They are similar to the Central Plains.

Therefore, if they want to survive, they have to rely on the Central Plains.