The fortress originated in Europe at the end of the 15th century, and has gone through a history of more than 100 years during the Chongzheng period of the Ming Dynasty.

The emergence of gunpowder weapons has made the original horizontal and vertical city into layers of fortresses, and the emergence of fortresses has also made the main form of European warfare shift from field warfare to siege warfare, because of the super defensive power of fortresses, European countries are keen to build fortresses, the most famous of which is France, and the construction of fortresses on the border is a major feature of France in the next few centuries.

However, it was Tsarist Russia that built the most forts, or maximized the effect of forts.

While the countries of the European continent built strong ships and cannons one after another, colonizing everywhere in the world, Tsarist Russia was silently expanding eastward along the land, and they successively destroyed the Golden Horde, the Crimean Khanate, the Kazan Khanate, and the Siberian Khanate, and the territory expanded dramatically, and the benefits obtained were no less than those of the European continental powers that seized colonies everywhere in the world.

In the battle against the nomads, they discovered a secret that was not a secret, and that was that the fortress was the nemesis of the cavalry!

It should be said that ordinary cities are also more restrained cavalry, but once the number of cavalry exceeds five times that of the defenders of the city, it can still be captured if it is attacked hard, but if it is a fortress, even if the number of cavalry exceeds ten times that of the defenders, it is difficult to conquer the fortress if there is no gunpowder weapon more advanced than the defenders.

Naturally, the nomadic tribes could not have more advanced gunpowder weapons than Tsarist Russia, so Tsarist Russia simply fought the Mongol-Yuan Khanate, which was dominated by nomadic tribes, with its fortress, unable to find the north.

It is precisely because the fortress is easy to defend and difficult to attack, the biggest advantage of the strong mobility of the nomadic tribe is restrained to death, as long as the fortress is repaired all the way through, stuck in the waterway, no matter how strong the mobility of the cavalry, it is also a dead end.

Tsarist Russia in the process of invading the major khanates, has tasted the great sweetness of the fortress, if the Ming does not come, their next target is the Kazakh Khanate, in the historical records in charge of formulating the plan to invade the Kazakh Khanate, the Russian Senate Secretariat civil officer Kirov once put forward a proposal, his suggestion is very simple, that is, in Orenburg and the Aral Sea in a short distance of more than 1,000 miles to build 45 fortresses, Tsarist Russia's enthusiasm for the fortress can be seen.

Of course, now that the Ming army has been overwhelmed, they probably have no chance to invade the Kazakh Khanate.

However, the fortress they built when they invaded the Siberian Khanate is still there, and in order to resist the Ming army, Rozov also ordered Golovin and Franzbekov to brave the cold and build a fortress in the Siberian Plain.

Although the army is not the cavalry with cold weapons of the nomadic tribes, and the gunpowder weapons of the Ming Dynasty are much more advanced than those of Tsarist Russia, it is also a headache to face the fortress, because the fortress is too difficult to attack.

The only time the Ming Dynasty conquered the fortress head-on was Chongzheng's seven years of recovering Dongfan, he conquered the Dutchman's Gerancha Castle, but that siege did not have any reference significance, because the Ming army used prisoners as meat shields tied to the siege vehicles to scare the defenders did not dare to open fire, and then used grenades to surprise a wave of surprise before rushing in, and at that time the Dutch defenders in the Geranza Castle were only 500 people, and the Ming army alone had 150,000 troops, and there were super battleships to cooperate, and the difference in strength between the two sides was too great. The Dutch simply couldn't hold it.

This time it was different, the Ming army detected nearly 500,000 defenders of Tsarist Russia, each fortress could not be only a few hundred people, and Tsarist Russia is not only one fortress, but everywhere there are fortresses, if the Ming army attacks comprehensively, it will be difficult to achieve absolute superiority in numbers, and if each is broken, the enemy may support at any time, or sneak attack from behind, after all, they are more familiar with the terrain than the Ming army.

Is it an all-out attack or a breakdown? Not only Sun Chuanting, Lu Xiangsheng and Cao Wenzhao on the front line fell into contemplation, but Zhu Cijiong, who was far away in the capital, also fell into contemplation.

He sent people to check the offensive and defensive records of the fortress, the most famous of which was the attack and defense of Metz in 1552 AD.

In May 1552, 5,000 French troops took the city of Metz in the Lorraine region by surprise, and half a year later, the Holy Roman Emperor Charles V began to besiege Metz with an army of 50,000 in an attempt to recapture it.

However, during this half year, the 5,000 French defenders had rebuilt a fortress behind the old walls of Metz, and as a result, Charles V led an army of 50,000 to storm Metz for more than a month without taking the city.

It was not that the firepower of the Holy Roman Empire was not strong enough, at that time, Charles V mobilized hundreds of cannons to bombard continuously, and a total of more than 7,000 shells were fired in one day, and the city walls collapsed hundreds of meters, but the fortress defense line behind was still intact.

Charles V organized numerous assaults but failed to capture the city of Metz, and in the end, the army of the Holy Roman Empire suffered heavy casualties and had to withdraw its troops.

50,000 against 5,000, attacked for more than a month, and finally the attacker suffered heavy casualties and had no choice but to retreat, this is the power of the fortress!

According to the density of the forts that have been discovered, Tsarist Russia has built at least 100 forts on the Siberian Plain, that is to say, if the Ming army attacks in an all-out way, each fort can send more than 10,000 people at most, it is simply a joke, even if the Ming army's weapons are advanced, it is impossible to attack them, so the plan of a full-scale attack was quickly rejected by Zhu Cijiong.

There is no way, you can only choose to break each one.

In order to accurately transmit the location information of the fortress in the telegram, Zhu Cijiong specially compiled a set of latitude and longitude coordinates, which are very different from the latitude and longitude coordinates of later generations, because the benchmark of this set of latitude and longitude is the capital of the Ming Dynasty, that is, with the capital of the Ming Dynasty as the center, draw a cross line, the left is the east longitude, the right is the west longitude, the above is the north latitude and the bottom is the south latitude, every hundred miles is one degree.

Although this set of latitude and longitude system is a bit troublesome in the calculation of time zones, it is relatively simple and easy to understand, especially convenient for marking the location, Zhu Cijiong can't care about the calculation of time zones, who has time to calculate the circumference of the equator and the distance between the north and south poles, first use the whole set of simple words.

To put it bluntly, the latitude and longitude coordinate system is to add basically equidistant horizontal and vertical lines to the map, which looks like a Go chessboard, which has been seen by anyone who has read a little book in the Ming Dynasty, but there is nothing unusual.

Soon, the map of the Ming army was painted with a layer of light-colored latitude and longitude lines, crisscrossing them, as if drawing a Go chessboard on the map, except that the latitude and longitude were marked at both ends of each line.

From then on, the Ming army did not need to send someone to pass the map back and forth with the map or explain it in the telegram through reference objects such as mountains and rivers for a long time, just report a coordinate directly in the telegram, which is absolutely accurate!