In order to obtain the support of the Khitan, Shi Jingjiao of the Later Jin Dynasty sent an envoy to Fengyanyun's sixteen states to officially cede the land of the sixteen states to the Khitan. After the Liao Dynasty occupied Youzhou, Yelu Deguang promoted Youzhou to Nanjing, renamed it "Nanjing Xijin Mansion", also known as Yanjing, as one of the Khitan companion capitals. The old city has not been enlarged on a large scale and has basically remained in its original appearance. The circumference of the whole city is thirty-six miles, the city wall is three zhang high, one zhang and five feet wide, the foundation under the city wall is eight zhang wide, the enemy tower, the war oar is complete. There are eight gates in the outer city, and there is a moat outside the gate, and a wooden drawbridge is erected on the moat, which is prepared for defense.

The Khitan takes Youzhou as Nanjing, the imperial palace is built in the city, there is a sub-city, also known as the imperial city, the inner city, and the Khitan lord lives in this city when he patrols Nanjing. The location is in the southwest corner, sharing the west gate and south gate with the big city. The main area of the sub-city is the palace area and the royal garden area, and the location of the palace area is biased to the east of the sub-city, and protrudes to the south beyond the walls of the sub-city. The east side of the palace area is the South Orchard District, and the west side is the Yaochi Palace Garden Area. The scale of the palace is larger, there is a small island in the Yao Pond, there is the Yao Pond Palace, and there is the imperial mansion next to the pool.

Due to the southwest location of the sub-city, there are only two main roads in the city that run through the whole city. One is the east-west main road, named Danzhou Street, which connects the Qingjin Gate and the Anton Gate; One is a north-south trunk road, connecting Gongchen Gate and Kaiyang Gate. The south gate and west gate of the imperial city are the same gate as the south west gate and the southwest gate of Nanjing, Liaoning. From the imperial city, through the Danfeng Gate or the West Gate can go straight to the suburbs. Because these gates are not opened, they are also called secret gates. The city is divided into 26 "fangs", each of which has a wall and a gate, and the name of the fang is on the door to manage the residents of the city.

Song and Jin jointly invaded Liao, and Yanjing City became the focus of contention. Song Liao and Song Jin launched several major wars here, and finally the Jin State occupied Yanjing City. It became the front line of the Song-Jin war, and the outpost of several southward movements. Jin set up a guard here, and guarded it with the general Sosuke. After Zhao Ta repelled the Jin army attacking the Song Dynasty, the position of Yanjing City became more important, and on the basis of the original, the city wall was repaired to increase the defensive measures, and it became a fortified city in the north...

After Yan Zongfu fled back from Zhuozhou, he launched comprehensive war preparations, and after receiving the news that Wushu had led troops back to help, he immediately had confidence. First gather the nobles of the city. Dahao explained the current Northern Expedition of the Song Army, and the war broke out again, requiring the officials and people in the city to defend Yanjing City to the death, and the people were in Yanjing City, and issued an announcement to recruit young people to help defend the city, and at the same time began to take measures to hoard grain and grass, military funds, and prepare weapons.

"Deputy Marshal, we only have 30,000 capable soldiers who can fight back to Yanjing City. Recently, various ministries have requisitioned and transferred young and strong soldiers of various ethnic groups to fill the army, expanding to 60,000 people, but most of the young and strong are Khitan, Han miscellaneous soldiers, and Bohai and Xi people who have been incorporated into Meng'an Mouke, and they lack training. Without a battle formation, it is inevitable that the city is so large that it will lose sight of one or the other. After Yan Xiyin and Zongfu inspected the city defense, his face was covered with gloom. I am not optimistic about the future, I said leisurely. And he saw that Sosuke didn't squeak, and then said. "The Song army attacked from Pingzhou and Hebei, it is said that there are 100,000 people in the two armies, and there are sharp firearms, how can we hold it with such a few people!"

"I know that we can't hold the road, but the matter is man-made, we must do our best, fight to the most and be loyal to the country." Sosuke stopped, held the battlements in his hand and looked out of the city, observed left and right for a while and replied, "The firearms of the Song army are sharp, the artillery fire is fierce, the city wall of Qigou Pass is not much worse than that of Yanjing City, but we can't help bombarding, we also have firearms in our arsenal, as well as trebuchets, which can be used against them, and we must also set up more obstacles outside the city to prevent the enemy from approaching the city gate." ”

"That's the only way, the only thing we can rely on is this city, the city gate on each side must be sealed, and at the same time, prepare materials for repairing the city wall, prepare more rolling wood and stones, organize archers to prevent the Song army from climbing the city wall, and be prepared to hold it for a long time!" Wanyan Xiyin nodded and said, he had doubts about whether the reinforcements could arrive in time, Zhao Er would not sit idly by and watch the reinforcements of the vultures enter the city, maybe this is his trick to besiege the city and send reinforcements, but the matter has come to this point, and he can only try his best to defend the city...

The history of human development is actually a history of war, the civilization of the Chinese nation is also built on the killing, during which a complete law of attack and defense was produced, and the attack and defense of the city in the Song Dynasty reached a peak, which made the thinking of the Qin, Han, Sui and Tang military strategists unparalleled.

The Jurchens are immediately able to win the world, they are also a nation that is good at learning, and they also learned to attack and defend the city in the war with the Liao and Song dynasties, and at this time, there are also the first Jurchen genius Wanyan Xiyin and many 'traitors' and 'Liao dogs' in Yanjing City to give them advice. Soon the city defense plan of Yanjing City was released, and the next day after the agreement was made, the Jin army forcibly recruited 100,000 migrant workers from inside and outside the city to start construction, and at the same time sent troops to 'collect' 200,000 stone grain and one million loads of firewood from outside the city.

A few days later, Yanjing City was built into a well-layered, offensive and defensive fortified city. The position spread out from the outside of the city thirty miles, and was divided into a barren circle, a warning circle, and a city defense circle from the outside to the inside.

Within thirty miles of the city is a barren circle, which is cleared of the wilderness by strong walls, and all that can be evacuated into the city is transported away, and if necessary, those that cannot be taken away will be burned and poisoned into the wells. Ten miles away from the city, he entered the warning circle. Extend the edge of the warning circle, and set up a reconnaissance post at the commanding height at certain intervals to form a cordon. After the reconnaissance post, a liaison post is set up every three miles to maintain the communication between the reconnaissance post and the city, and the flag is raised during the day and the fire is raised at night. In addition, mobile squads should be set up at key roads and checkpoints to be responsible for reconnaissance and counter-espionage. This three-in-one cordon will be withdrawn when the enemy army enters the outskirts of the city and is about to besiege the city.

The edge of the city's defense ring is where the long-range weapons are fired, and all objects outside the city within this range are bulldozed to clear the angle of fire and sight. Ten zhang away from the root of the wall is a moat, and there is water in the moat, and bamboo thorns of different lengths are staggered and planted half a foot below the water surface. The moat outside the city gate will be erected on the bridging bridge, this kind of bridge has only one beam, the two ends of the beam extend from the edge of the crossbeam, when the enemy walks to the bridge, pull the mechanism to retract the crosswood, the bridge deck will be overturned, so that the enemy will fall into the trench.

After the moat, a low rammed wall was added, and soldiers were deployed behind it, waiting for the enemy to enter the moat or trench, and cooperate with the defenders of the city to kill or burn it with firewood and grass. Further inward, there is a wide and wide belt to resist horses, which is mainly used to hinder the approach of the enemy's ladder. In the areas where the defenders entered, the horses would be buried in a shallow state that could be easily moved, and the top of the castle would be marked. At the end, within a foot of the wall are a series of staggered pointed wooden stakes that rise a foot above the ground, which have the function of preventing enemies from climbing the city and stabbing them to death.

Then there is the city wall, which is the most rear-back barrier to enter the city. The width of the top of the Yanjing city wall is enough for the defenders to move and fight freely on it. On both sides of the extension wall, there are female walls three feet thick and five feet high, of which the outer female wall is higher and has shooting holes wide on the outside and narrow on the inside. In addition to the permanent corner towers, a large number of temporary towers were added to the extension walls. Every fifty steps, an observation tower was built that jutted three feet out of the outer wall.

In addition to the horse face, every 100 steps to build a protruding outer wall of the city wall to eliminate the dead corners of the city and flank the enemy under the city of wooden towers. Similarly, every 100 paces, there is also a horizontal wall made of high-pointed wooden piles, which is usually opened for passage, and closed as a roadblock after the enemy army enters the city. Every 300 paces after the end, a wooden building protruding from the inner female wall was built to prepare for attacking the enemy entering the city.

The root of the Yanjing city wall is more than ten zhang thick, even if the city foundation is hollowed out, it will not collapse due to the loss of the center of gravity. The Jin soldiers dug out from the inside of the city every about 200 steps, and stopped when they approached the outer wall half a foot, forming a secret door for surprise killing. Inside the secret door there are also kilns with bellows, firewood and straw, and obstacle carts in case the enemy finds them, and when they enter them, they smoke and block the passage. Under the city tower, the city gate is set up inside and outside the city gate hole, and there is a hanging door that rises and falls in the middle of the door hole. All three doors are equipped with movable perforations. In order to defend against fire, in addition to preparing water jugs and long-handled sacks in the gatehouse, the gates were wrapped in iron sheets or staggered round wooden stakes with thick mud nailed to the outside of the gates.

Compared with the step-by-step fortification outside the city, the inside of the city is a smooth scene. The wide road on both sides of the gate and at the corner of the city connects the ring road paved by the extension wall. The ring road is connected to the main roads, forming a network that extends in all directions in the city. However, the city is not a place to drive straight into, after the ring road also built a rammed earth low wall, in front of the wall dug a deep, wide ditch of one zhang each, the ditch is stuffed with firewood and grass, once the enemy army enters the city, it can ignite firewood and grass to form a wall of fire, and according to the wall and the city wall friendly attack on the ring road.

In terms of defensive tactics, in addition to the defensive and offensive defense and flexible and careful deployment, in order to resist the power of the Song army's artillery, Wanyan Xiyin also came up with a new tactic of using artillery against artillery. The so-called artillery against artillery is to use a catapult with a range of 300 paces to attack the Song army's headquarters and artillery positions; Attack the positions of the well-trained engineering troops of the Song army with a catapult with a range of 200 paces; After the end, he attacked the forward siege equipment position of the Song army with a catapult with a range of 100 paces. At the same time, in order to prevent counterattacks and reduce the difficulty of transporting stone bullets, the catapults were not set up at the head of the city, but were hidden on the inner side of the city walls, and were directed by observation posts on the head of the city.

Zongfu looked at the offensive and defensive city and the stone-throwing cart arranged under the city densely protruding with long arms, and finally showed a smile, and he had a bottom in his heart, and felt that he should let Wanyan Xiyin write down the four big words of 'solid as gold' and hang above the city gate. It's a pity that Zhao Er didn't give him a chance, because he saw from a distance that the liaison posts outside the city were erected with five large flags of various colors, which was a signal that the Song army was approaching the outskirts of the city. At this time, someone came to report, and the north of the city also found that the Song army brigade was coming... (To be continued......)