"The previous eleven Northern Expeditions of the National Dynasty had already dealt heavy blows to the Beiyu, so that the Beiyu did not dare to approach the border fortress easily, and could only harass them in Daning and Kaiping."

On the tenth day of the first month of April, accompanied by Zhu Gaoxu's voice sounded in the study, Zhu Gaoxu was taking Wang Xuan and Yang Zhan to analyze the sand table in the study.

Zhu Gaoxu pointed to the north of the sand table with a branch, self-analysis from north to south, while Yang Zhan and Wang Xuan listened to the lecture and recorded what Zhu Gaoxu said.

After 10 days of analysis, coupled with the information obtained from visiting and inquiring about Bao Taowei, Hezhou Wei Qianhu, and the command envoys, Zhu Gaoxu probably came to Zhu Yuanzhang's military attitude towards the north and the localities.

"The national dynasty occupied Hexi and Monan with important towns such as Yijinai (Ejina Banner), Ningxia, Dongsheng (Hohhot South), Kaiping (Duolun County), Daning (Chifeng), etc., and sent Tang cavalry to constantly patrol the border, borrowing land to help the military with land and horses, reduce the pressure on the Guan, and protect the people in the Guannei."

"Specifically, the main center of the first line of defense in the north of the country is in Dongsheng, Dongsheng is connected to Kaiping, Dushi, Daning, Kaiyuan and other places in the east, and Helan Mountain and Beishan in Gansu are connected to the west, which is on one side."

"The characteristics of the first line of defense are that 'the terrain is straight, close and easy to defend', and the disadvantage is that the land is vast and sparsely populated, and the long-term stationing of troops consumes national strength."

Zhu Gaoxu said as he pointed out the northern cities with a branch.

Yang Zhan's pen and ink in his hand flew quickly, and he wrote down what he said one by one.

"The second line of defense of the dynasty is the vassal king system formulated on the basis of 'respecting the king and conquering the country', guarding the border fortress and expanding the territory."

"This system starts from Suzhou in the west to Liaodong in the east, and the king of Yanbian is not enough to cover the danger, and controls the fortress, accompanied by the general of Yuan Rong, and the power is to control the life, and the power is comparable to the army."

"The Saiwang system, you can clear the desert when you enter, and you can defend the tents to face each other, once the northern captives are strong and the first line of defense is difficult to suppress, you can make the Saiwang go out to patrol the border."

"Although it is called patrolling, it is mainly to encircle and suppress the remnants of the northern captives, weaken the number of northern captives, and prevent the northern captives from lifting heavy troops to the south."

When Zhu Gaoxu spoke, he would be silent for a moment from time to time, which was thinking about why Zhu Yuanzhang arranged it this way.

However, his thoughts are quick, often only taking a few breaths to figure it out, and then he talks about the third line of defense:

"The third line of defense of the dynasty is the defense line formed by the Qin, Zhou, Lu, Qi and other domains relying on the Weishui Yellow River and the Qinling Huai River at their back."

"Although the guards of the four feudal lords are few, the three feudal domains of Shu, Chu, Hunan and Nanzhili, which rely on the fourth line of defense, can support each other."

"At the same time, because the fourth line of defense is located in the upper reaches of the Yangtze River, it can rely on water conservancy to support Nanjing City at any time."

"However, this also means that the city of Nanjing is very vulnerable to the threat of the three feudatories, especially the feudal states in Jingzhou and Wuchang, and the Hunan and Chu domains of the Yangtze River waterway are next to it, so the two locations of Jingzhou and Wuchang are extremely important."

"Generally speaking, the whole set of arrangements is to rely on the north-south depth of the national dynasty to carry out hierarchical defense, and arrange such as Jin, Zhou, Chu, Hunan and other feudal domains on the central line, ready to support the eastern and western fronts at any time."

"However, there is a huge flaw in this system, that is, the geographical depth is too long, although it is suitable for defense, but it is not suitable for attack."

"The border armies in various places are too scattered, and the assembly time is too long, once the main force of the defense line is out of the block, the defense line will immediately weaken, and it is very easy to be attacked by the northern captives."

"Therefore, the imperial court must gather another army of soldiers and horses, so that after the army is out of the fortress, it will be used to replace the task of border defense."

"This army of soldiers and horses is the Imperial Leopard Taowei and the Hezhou Guard......"

Zhu Gaoxu told all of Zhu Yuanzhang's intentions, which made Yang Zhan, who recorded it, and Wang Xuan, who was listening to the class, dry.

However, Zhu Gaoxu did not pay attention to their state, but propped his hands on the sand table, his brows tightened.

He figured out Lao Zhu's arrangement, but at the same time, he also knew the difficulties Lao Zhu faced.

Yuqian Leopard Taowei and Yuqian Hezhou Wei are the elite of the elite of the Ming army, and they are indeed capable of undertaking the defense work after the main force of the border army is out of the fortress.

But the problem is that they are too few in number and too few in horse.

Therefore, if the attack of the Beiyu is frustrated, and then it is turned in, the two cavalry will never be able to catch up with the main force of the Beiyu, which is why Zhu Yuanzhang is in a hurry to buy horses.

An elite cavalry must have at least one riding horse, a pack horse and a military horse, so as to maintain the high mobility of this army.

Since it was a defensive war, the Ming army did not have to worry about supply problems, what they had to do was to send troops to monitor the main force of the northern captives after the northern captives detoured south, so that the main forces of the northern captives did not dare to raid the interior easily.

However, according to Zhu Gaoxu's news from Bao Taowei and Hezhou Wei these days, it seems that Bao Taowei and Hezhou Wei only have one riding horse and one military horse, and they have no pack horses.

As for the Ming Dynasty, there are only more than 40,000 horses in the whole world.

While maintaining a certain number of cavalry in the north, it was necessary to maintain two guards cavalry of 7,000 men.

It can be said that Zhu Yuanzhang has tried his best to solve the problem of going north and south in the future, and Daming has also reached its current limit.

From a military point of view, Zhu Yuanzhang has achieved the extreme, and Zhu Gaoxu has no solution to this problem at all.

"How did my cheap daddy solve this problem......

Zhu Gaoxu looked at the sand table, puzzled.

At this time, even if he wanted to write a letter to ask his cheap daddy, he didn't have time.

"It seems that from a military point of view, it is difficult for me to excel."

Zhu Gaoxu was suddenly deflated, although he made rapid progress, but that was only theoretical.

He thought that he was not a military genius, and naturally there was no way to use the current resources of the Ming Dynasty to break the situation of the invasion of the north and the south.

Wang Xuan on the side saw that Zhu Gaoxu was silent, and knew that he couldn't think of a way to go further, so Wang Xuan looked at Yang Zhan, and then stubbornly said:

"Your Highness, we can't go any further on defense, so why don't we turn to attack?"

As soon as Wang Xuan's words were spoken, before Zhu Gaoxu could speak, Yang Zhan shook his head and said, "It's too difficult to attack......

"The problem with the Northern Expedition is not that our soldiers and soldiers cannot defeat the other side, but that the north of the country cannot support too many soldiers and horses in the Northern Expedition."

Yang Zhan said the reason why he couldn't attack, and Zhu Gaoxu also bowed slightly when he saw this, and then pointed to Liaodong, Beiping, Shanxi, Shaanxi and other places with the branch in his hand.

"The northern part of the country is vast and sparsely populated, among which Liaodong is full of military households, military households and their relatives, judging from the results of last year's inventory, the number of mouths is still less than 400,000."

"There are less than 2 million people in Beiping, 4.1 million in Shanxi, and only more than 2 million in Shaanxi and Gansu, most of which are naturalized people from Semu, Xifan and Beiyu."

"Even if the number of mouths in the above provinces is reduced by 40%, the number of men is only more than 3 million."

"At present, there are no less than 500,000 people living in Mobei, and nearly 200,000 men."

"Even if my Han'er is one against two, I will send 100,000 troops."

Speaking of this, Zhu Gaoxu couldn't help but sigh: "100,000 soldiers and horses, according to the distance, I'm afraid it will take 500,000 men as people to support the army approaching Kulan and losing temperature." ”

"If the northern captives flee and the army returns in vain, the losses caused will be millions or hundreds, and it will be difficult for both the dynasty and the people to bear it......"

During the conversation, Zhu Gaoxu had already given up persuading Zhu Yuanzhang to go on the Northern Expedition, because if he fought like this, the northern provinces would have to recuperate for at least several years before they could recover.

From this point of view, Zhu Yuanzhang's strategic arrangement of layers of defense is indeed impeccable, at least for now.

At this moment, Zhu Gaoxu understood the gap between himself and Zhu Yuanzhang, as well as Zhu Di.

However, he didn't think he would fall behind forever.

People will grow, as long as there is a platform, he Zhu Gaoxu does not believe that he will always stand still.

One day, he will change the strategy and tactics of the Ming Dynasty, and transform the hierarchical defense into a point-like distribution and focused defense.