Lu Chengqi carefully studied the map and found that where Goryeo and Dashun bordered, there was no place to attack except for the Yalu River. In other words, as long as the area around the Yalu River is held, there is not much Goryeo can do.

It's just that the territory of Dashun only covers the lower reaches of the river, and does not occupy all of the Yalu River. The lower reaches of the Yalu River are the dividing line between Dashun and Goryeo; The middle reaches are the dividing line between Goryeo and Liao; The area where the upper reaches and Changbai Mountain are combined is the dividing line between Goryeo and Jurchen.

In fact, it is really not easy for Goryeo, it is sandwiched between the two superpowers, there are bitter words, and there is a bad neighbor Jurchen. In fact, the harm of the Jurchens to the Goryeo Kingdom was far greater than that of the Liao Kingdom. Goryeo's change to the suzerainty is actually to let the Jurchens restrain themselves and stop causing trouble to Goryeo. After all, the Liao State is strong, and the Jurchens also know it. Even between the Jurchens and the Khitan, there have been many wars.

In order to resist the burning and plundering of the Khitans and Jurchens, Goguryeo's predecessor also learned from the Central Plains and spent 16 years building the Great Wall. Because of the topography, the Great Wall of Goguryeo is only a thousand miles. When the Wang family usurped the power of the Gao family in Goguryeo, the thousand-mile Great Wall did not seem to come in handy. However, as Goryeo's status gradually became awkward, the thousand-mile Great Wall finally came in handy. There were Jurchens in the front, Liao in the middle, and Dashun in the back, and Goryeo had to garrison troops on the border for defense.

According to the attributes of the farming nation, the defense must be defended by leaning on the city, and the battle line is so long, it is natural to build a city wall. This is also why China was able to build the Great Wall, the battle line is too long......

Now that Dashun has fallen out with Goryeo again, Goryeo naturally does not dare to take it lightly. Liao and Dashun signed a three-year non-aggression pact. What if Daesoon took this opportunity to attack Goryeo? This is not the canonical history. Both the Sui and Tang dynasties failed in their attacks on Goryeo. Let the Goryeo stick have no fear. On the contrary, Goryeo and the Central Plains have always had a good relationship, and in the eyes of Goryeo, the Central Plains is a terrible opponent, and if the Central Plains attack Goryeo, it will really be a mess.

In fact, it was impossible for Dashun to attack Goryeo at this time. Because at this time, the global climate entered the Xiaoice period. Don't think that the Xiaoice River period only existed in the Ming Dynasty. Even in the official history, the Song Dynasty corresponding to Dashun also had the Xiaoice River period. Although there were no meteorological instruments to observe climate changes in ancient times, there were rich records of "phenology". "Phenology" refers to the time of year when people observe frost and snowfall, rivers open and freeze, plants bloom and knot, migratory birds come and go in spring and autumn, and so on. China was founded on agriculture, and for the needs of agriculture, there were observations of "phenology" since the Western Zhou Dynasty.

According to records, Chang'an, Kyoto, of the previous dynasty. There are still plum trees in the palace, and citrus trees are planted. And there is no record of snow in Chang'an. Until more than 60 years ago, Chang'an could no longer plant plum trees, and heavy snow had to fly every year. Since his rebirth, Lu Chengqi has also felt that unlike the urban heat island effect in later generations, this Chang'an City is really cold. If you don't burn a brazier in winter, you won't be able to stay in the house at all.

The growth of lychees is also a good proof, more than 60 years ago, Chengdu also grew lychees, but now only Meizhou, the hometown of the talented Su Shi, can grow lychees. All this shows that the temperature at this moment has indeed entered a very cold period, even if it is the Xiaoice River at the end of the Ming Dynasty, it is just so, right? History can change, but the temperature cannot deceive people, and the Xiaoice period came as scheduled.

In such cold weather, let alone attacking Goryeo, even if it is to defend your own country. Lu Chengqi even suspected that the fall of the Song Dynasty had a lot to do with the weather. When Jin destroyed the Northern Song Dynasty, it happened to be in the middle of winter in December. Note that this is the twelfth month of the lunar calendar, when it was also the Xiaoice River period, the Central Plains Han people did not have cold cotton jackets, the clothes to be used by the poor democracy were linen cloth, or fabrics woven from other plant fibers, and silk satin belonged to the upper class or wealthy families. Ordinary people, in winter, wear **, wear straight jackets, travel also need to wear hoods, etc. If you are a wealthy family, in addition to wearing silk and satin, you will also wear a crane, which is a very expensive fur coat, as well as a variety of fur capes and hats, and the common people are the same heaven and earth.

Most of the soldiers are poor people who are bitter, and the enemy is attacking in winter, and they don't even have the strength to defend themselves on weekdays, how can they resist the enemy? Naturally, it was a fiasco...... The nomads are different in that their clothes are mostly animal fur, warm and thick, and their movement in winter is not inferior to that in summer. Under the elimination of one and the other, it is not uncommon for Jin to destroy the Northern Song Dynasty.

Of course, there are many other factors in this, and key factors such as the policies, civilian officials, and military of the Northern Song Dynasty are also very fatal. If you don't want to repeat the mistakes of the past, you have to change little by little.

To change the habit of dressing, the development of cotton is naturally the best. Even if you can't find cotton for a while, you can find a substitute, kapok. Lu Chengqi remembered that there were a lot of kapok in Fujian and Guangzhou, and if they were planted vigorously, they would be able to solve the problem of cold protection and warmth.

After solving the problem of keeping warm, when the road is repaired, Dashun does not dare to say that he has the strength to attack, and he can also protect himself.

After thinking about it, Lu Chengqi felt that this matter should not be delayed, and hurriedly called the newly appointed secretary of the Ministry of Industry, Li Jie, because he really couldn't think of anyone who could do this. When Li Jie was summoned to see him, he didn't dare to hesitate, and hurriedly followed the attendants to the palace.

It is impossible to say that Li Jie is not apprehensive in his heart. Just a few days after taking office, he was summoned to meet him, "Could it be that something is wrong with me?" Li Jie had to think so.

After entering the Vertical Arch Hall, Lu Chengqi, who was studying the map, raised his eyes to look at him and asked, "Li Qing, can you read the map?" ”

Who is Li Jie? A man of erudition and talent, not to mention a map, can draw detailed engineering drawings. Immediately said: "Back to Your Majesty, the minister understands a little." "This Vertical Arch Hall is something that Li Jie has never been to before, because he didn't have this qualification before, so naturally he couldn't enter the Vertical Arch Hall to meet Lu Chengqi in private.

"Then how about Li Qing look at this map?" At this moment, Lu Chengqi's heart also has a hint of showmanship. After all, the map of the world behind his desk and chair has gathered the greatest strength of the Supervision Division, and the depiction after field investigation is much more accurate than any map. With Lu Chengqi's knowledge, even if this map can't be all right, it can be worth six or seven points. In this era when there are no satellites, it is also a very powerful thing to do this. Where is it like other maps presented to the emperor, using realistic techniques to depict mountains and rivers, but the proportions are worrying. Maybe it was to make the emperor look better and understand that he painted the mountains and rivers so three-dimensionally. But the proportions are wrong, and no matter how delicate the painting is, it is in vain.

Li Jie is everyone, so he can naturally understand this map. Combined with his own knowledge, Li Jie suddenly found that this map was even more accurate than he imagined, and he couldn't help but take a few more looks, and said: "Your Majesty, who is the hand of this map, it is simply a treasure of the world!" ”

Lu Chengqi smiled and didn't answer, and asked rhetorically: "Li Qing, I came to you not just to look at the map. As the secretary of the Ministry of Industry, in addition to being in charge of the world's water conservancy, tuntian, transportation, etc., the people's well-being also has to be questioned, right? ”

Li Jie was stunned for a moment, and said honestly: "Your Majesty, the minister has never heard such a statement. (To be continued.) )