The earliest bastions can be seen as an evolved version of the tower, essentially changing the fortress from a convex polygon to a concave polygon, so that attacking any point in the castle would expose the attacker to more than one bastion (usually 2-3), and the defender could use crossfire to perform multiple strikes. Prior to the * era, the walls of forts were usually built tall and reinforced with stone or brick, with towers or horse faces for additional firepower. If anything, some particularly fortified cities have more than one wall.

Bastions originated in Italy at the earliest time, and the interval between Italian bastions and bastions was large, and the bastions were perpendicular to the city walls and had obtuse angles in shape. It is still stonework and tall, with only one significant improvement, and that is the side-firing fire. The cannons placed on the bastions can fire longitudinally at the moats, thus achieving an effective blockade, but there are still some blind spots in the bastions themselves. Therefore, at this time, it is necessary to build a triangular fort to strengthen the defensive capability of the fortress. This is the significance of the triangular bastion.

The Triangle Fortress was only 3,4 feet lower than the main fort, allowing the main fort to shoot beyond the horizon, and the defenders above the Triangle could form part of the crossfire. In order to prevent the enemy's attack, there are many horizontal walls set up in the concealed road, and sometimes the concealed road is directly built in a zigzag, so there is no need for a horizontal wall.

The outermost ram is where the crossfire is most concentrated, and its angle of inclination helps the defender to exert firepower. The entire fortress will be built with masonry as much as possible, and if it has to be used for some reason, the outside will be covered with thick soil. Because the soil layer can absorb energy, the masonry is not only easy to damage, but also prone to ricochet, which can lead to serious casualties.

In the Dutch bastion system, there were usually several ditches with gates. Most of the trenches were dry, and when the enemy crossed the trenches, they flooded the enemy, which was also characteristic of the Low Countries of the Netherlands. In addition to the above-mentioned facilities, in order to prevent the enemy from digging holes and blasting (usually after the attack reaches the inclined embankment, otherwise the distance is too long to ensure the oxygen content), the defenders will also dig corresponding tunnels underground. After determining the location through a special listening tunnel, they will send people into the corresponding tunnels to eliminate the enemy digging team, or directly fill the sulfur. This kind of fighting in the dark is very brutal.

More than 1,000 years later, in the Ming Dynasty, the Dutch had built the city of Geranza in Taiwan, which was part of the fortress, which was later captured by Zheng Chenggong through a long-term siege for nearly a year.

There are far more shapes than this kind of fortress, there are also common corner forts, crown forts, etc., in general, the more sides of the polygon, the more shooting directions, and the better it is to cover each other.

While building a bastion was laborious and costly, besieging it was almost as time-consuming and labor-intensive, often lasting months or even years. During the limited war-time seasons of the year, a commander would be lucky if he could conquer one or two forts. This, in turn, has further stimulated countries to build fortresses. The most famous of these is Vauban on the French border, and Paris has become a major fortress. Until the time of the French Revolution, the vauban fortresses played a huge role in the fight against the anti-French alliance.

In this book, the protagonist Yin Lang is located in the Northeast, and the future will also be based in the Northeast, in addition to the consideration of severe cold factors, here the fortress is written in the book as a cross-era product, in order to enhance the strength of the protagonist, you can say, it is useless to build a castle, the strongest fortress is broken from the inside, the human heart is the most important, the protagonist in this book is too superstitious fortress war, maybe only a strong fortress can make the protagonist have a sense of security in this world.