Along the way, Yang Wen and Ouyang Xuan talked side by side. While he recounted the situation of the Yang family in Banzhou, he also introduced the reasons for moving the Zhisho and the Yang Mansion to Hailongtun. In fact, the reason for the construction of Hailongtun is very simple, that is, to resist the invasion of the Mongolian army and the Dali barbarians driven by it. Since the Mongols destroyed the Dali Kingdom, they have repeatedly invaded Banzhou and tried to attack the hinterland of Sichuan through the border of Banzhou, so that there are frequent peaks and fires in Banzhou.

The Banzhou army was brave and good at fighting, and although it thwarted the invasion of the Mongol army many times, its own losses were also very large. War is a gold-swallowing beast, the Yang family is only a few states, and the people under their rule are less than a million, and they have to fight against the powerful Mongolian army for a long time, and the economic pressure is extremely great. In particular, Banzhou City, where Yangfu is located, has a flat terrain and is convenient for land and water, and the economy is quite prosperous but there is no danger to defend, and it is really not suitable to be used as a place of governance in the face of frequent invasions of foreign enemies. After many trade-offs, Yang Wen began to consider choosing a steep terrain to build a fort. Although this method invests a lot of manpower and resources in the short term, it can make full use of the strengths and avoid the weaknesses, fully restrain the advantages of the Mongolian cavalry, and in the long run, it will also consume the least and maximize the benefits.

The battlefield in central Sichuan is a typical mountain castle defense operation mode. Since the Mongol army Wang Dechen's troops occupied Lizhou, they frequently sent hussars to plunder, stirring up a miasma of smoke and chaos in various prefectures and counties. After Yu Yu was appointed as the envoy of Sichuan, he built a mountain city and moved the state and county government offices into it, which not only sheltered the people, but also restrained the invasion momentum of the Mongolian army. Banzhou was able to build mountain castles and defensive warfare, and Yu Yu relied on the talents of the Banzhou Ran brothers to build a mountain castle defense system with the "Eight Pillars of Sichuan" as the core. A few years earlier, Yang Wen had also begun to build castles in Banju to resist the Mongol invasion. It's just that governance is the foundation of a place, and it is really not allowed to be careless. There are too many factors involved in choosing a new treatment, and there are many opposing voices within him, which makes him unable to make up his mind. In fact, he had already sent people to find a suitable place in the surrounding area as a new place of governance

What made Yang Wen make up his mind was the imperial court order brought by Lu Wende two years ago - to build a city to protect the Mongolian army. After the Mongol army Wang Dechen was stationed in Tunlizhou, he frequently attacked southward, which had exhausted the Sichuan Song army, and if the Mongol army stationed in Tundali broke through Banzhou and went north, Sichuan would be difficult to hold. If Sichuan loses, Jingxiang will not be protected, and the Mongols will be able to go down the river and go straight to Lin'an. Therefore, Lin'an sent Lu Wende to discuss the matter of Banzhou's resistance to Mongolia, and he and Yang Wenyi "put a city to think that Banzhou is the root", so he built "Longyan New Town", also called Longyantun or Hailongtun.

Since the end of the Tang Dynasty, Banzhou has not been actually under the jurisdiction of the central court, but is only nominally under the orders of the imperial court. However, on the one hand, the imperial court order met the interests and needs of Banzhou, and on the other hand, it also helped Yang Wen suppress the opposition voice, so it was quickly and efficiently implemented. For this reason, Yang Wen poured his efforts, mobilized 80,000 people, and it took almost two years to build this fortified city. In fact, the finishing touches of Hailongtun were completed just before the marriage between Banzhou and the Perak Army, and it was only two or three months since the Yang Mansion and Banzhou Yamen moved in. Yang Wen just took advantage of his daughter's wedding to celebrate.

When we arrived at Hailongtun, it was already sunset. Ouyang Xuan followed behind Yang Wen and walked up the steep and narrow mountain road. While listening to Yang Wen's introduction, he took a closer look at this fortified city. This sea dragon tun dwells on the top of Longyan Mountain, surrounded by streams on one side and three sides. There are hundreds of meters high cliffs all around, although "birds and apes cannot be crossed", only a narrow path in the southeast leads to the top of the mountain. Because the mountain is high and steep, the slope of the path up the mountain is extremely large, and ordinary people are so tired and out of breath even if they walk up empty-handed, let alone brave the arrows and stones to attack the city.

At the waist of the mountain is the first pass formed by the tall walls of several hundred meters. The city wall is made of bluestone and lime glutinous rice slurry, and the solidity is not lost to the reinforced concrete soil, and the defense power is very amazing. The only way to reach the wall is a walkway less than a meter wide, with 36 high and steep steps, known as the ladder. On the chest of the mountain is the second layer of passes, called suspension bridge passes, which are carved into the city gate by using the natural stone moat on the half-cliff. On the shoulder of the mountain is the third pass, this pass has three huge city gates, and there are many city defense facilities such as urn city, arrow tower, horse face and so on.

By the time we reached the top, it was already dark. With the last touch of the setting sun, Ouyang Xuan was surprised to find that the top of the tun was very flat and vast, and he could not hope to reach the illusion in the twilight. According to Yang Wen's introduction, the area of Tunding is close to 3,000 acres, and there are not only hundreds of houses, but also school fields, barracks, granaries, warehouses, and even many ponds and farmland. As long as there is enough food, you can hold on for a long time. Ouyang Xuan sighed when he heard the introduction, this terrain is even more steep than Diaoyu City, even if Meng Ge Khan arrives in this city, he will end up even worse. Yang Wen laughed when he heard this, with the firearms brought by the virtuous son-in-law, no one can break my strong city!

When I walked to the middle of the top of the tun, it was already dark. The light of the sparkling fires came through the doors and windows of the houses. Led by a Banzhou official, the Perak Army followed Yang Wen into a brightly lit hall that was specially prepared for them for a welcome banquet. At this time, nearly 100 people were seated in the main hall, and when they saw Yang Wen coming in, they got up one after another. Yang Wen walked straight to the main seat of the main hall, and motioned for everyone in the Thunderbolt Army to sit in the guest of honor. Following Ouyang Xuan into the main hall, in addition to Lu De, there were also Dong Hu and Zhu Xuanzi. Ouyang Xuan raised his eyes and looked around, only to see that most of the people sitting in the main hall were men with cloth scarves on their heads, and most of them were local mountain people. There may be a few women dressed as Miao Jiang in the middle, but they didn't see Yang Yan, which made Ouyang Xuan feel a little disappointed.

After the master of ceremonies in the hall signaled silence, Yang Wen began to speak. He first welcomed everyone to Hailongtun to participate in Yang Yan's wedding ceremony, and then introduced everyone in the Thunderbolt Army one by one - of course, the imperial court official titles introduced, and everyone also stood up and bowed their hands. When the people in the palace learned that Ouyang Xuan was the deputy envoy of Chengdu Road and the commander of Yongkang at a young age, they couldn't help but exclaim, and praised him as the dragon and phoenix among the people, and congratulated Lord Yang in unison for finding a good son-in-law, and the two sides had a good marriage. After speaking, the master of ceremonies began to toast, and everyone began to eat meat and drink wine in large bowls.

Yang Wen heard the praise in the hall, and he was quite proud in his heart. Yang Yan's marriage was originally his heart disease, but now it has become a beautiful marriage, not only his daughter is satisfied, but he is also extremely satisfied. What's more important is that he married the Thunderbolt Army, and even one of his biggest concerns. This concern stems from the succession of his only son, Yang Bangxian. He has been leading troops to fight all year round, and he has no eyes on the battlefield, and once there is a mistake, the issue of succession will inevitably lead to many disputes. Although Yang Bangxian has practiced martial arts since he was a child, he is only thirteen or fourteen years old this year, and his experience and qualifications are difficult to suppress various forces in the country.

Since the end of the Tang Dynasty, the Yang family has been in Banzhou for nearly 400 years. In the past 400 years, although his rule has also had crises, it has survived one by one with the endorsement of the imperial court, the support of its allies, and its superb strategy. It is an eventful time at the moment, the Southern Song Dynasty regime is already in danger under the iron hooves of the Mongolian army, the big families and surrounding forces in Banzhou are also ready to move, and the Yang family has always been thin, and this difficult situation inside and outside makes Yang Wen unable to sleep at night.

Yang Wen took advantage of the marriage event this time to invite the chiefs of the major families and surrounding tribes in Banzhou to come. On the one hand, it is to show the indestructibility of Hailongtun and the military might of the Banzhou soldiers, and on the other hand, it is also to show that the Yang family not only has the support of the imperial court, but also has unbreakable allies, so as to deter potential dissidents.