The top management of the Perak Army originally thought that it would be very difficult to cultivate 20,000 mu of land in 20 days, but at the end of the day, the results were surprising - 30,000 mu! According to Li Shuang, who is in charge of government affairs, said at the Tuntian commendation meeting, this achievement was not easy to come by. The reason why so much arable land can be reclaimed is not only that the land was originally fertile land more than ten years ago, but also because of the high-quality iron farming tools and effective organization, and even more because of the hard-working and high morale of the soldiers and civilians under the rule of the Perak Army. Ouyang Xuan personally announced the commendation decision and awarded awards to the commended personnel. The winners are not only blacksmiths who produce agricultural tools, but also agricultural technicians and managers, and more farmers who control ploughs and turn over the soil, and the representative figure is Yang San, who invented the "Yang San cultivation method" - now has been appointed as the head of agricultural technology at the Huaguoshan Reclamation Point.

As soon as the tuntian outside the mountain ended, the Thunderbolt army devoted their energy to the construction of Yokohara Fort. Because the spring in the Jiguan Mountains is about half a month later than outside the mountains, it is now the time for farming. Due to the new 60,000 acres of cultivated land in the mountains, in addition to the labor force of each village, it is still necessary to transfer personnel from factories and mines to help cultivate, so the construction of Hengyuan Fort did not involve too many migrant workers. However, the number of people involved in the Yokohara Fort project still reached 3,000. In addition to the 500 workers of the construction company and the 1,500 civilian workers who were transferred, 1,000 Perak soldiers were also drawn to participate in the construction of the fort as long as they had no military duties. These 3,000 people are only construction personnel, and if you add the production and transportation of cement, stone, wood and other materials, the personnel are even larger.

The reason why such a huge amount of manpower and material resources were invested in the construction of Hengyuan Fort was because Ouyang Xuan knew that the Songmeng Sichuan battlefield was about to undergo great changes, and if he missed the window period for the development of the mountain, the Thunderbolt army would be locked in the deep mountains. The reason why the envoy sent by Pan Tongzhi dared to threaten Ouyang Xuan was because Pu Zezhi was in a good situation when he attacked Chengdu, and he believed that he could defeat the Mongol army in Xichuan in a few days, and even expel the Mongols from Sichuan. But Ouyang Xuan, who is familiar with this history, knows that after Liu Heima occupied Chengdu, the Mongolian Khan Meng Ge sent Atahu to defend Chengdu. Atahu took advantage of Meng Ge's favor and did not take Liu Heima seriously at all, so that the Xichuan Mongolian army was not in harmony. It is not true that the Song army killed Atahu in the street battle in Chengdu, and even drove the Mongolian army out of Chengdu for a short time, but this is the return of the Sichuan official army. After the death of the arrogant Atahu, on the contrary, the Mongolian army had no internal friction, coupled with the return of the Mongolian army Wang Shixian stationed in the north of Tunchuan and the new reinforcement of the Mongolian army in eastern Sichuan, Pu Zezhi's tens of thousands of officers and troops were defeated, and had to retreat to the east and south of Sichuan along the river, and the state capital in western Sichuan fell into the hands of the Mongols. The top priority of the Perak Army was to build Yokohara Fort into an impregnable military fortress, so that they could gradually control western Sichuan and make the land of abundance a base for the anti-Mongolian cause.

The geographical location of Hengyuan Town, which is connected to mountains and rivers, is extremely conducive to business and trade activities, and you can imagine how prosperous it was back then. The site at the beginning of its construction is the first heavy traffic, and the village is a horse and a flat river within a radius of several miles. Yokohara Fort was not chosen in the location of the old village, but in a location closer to the former mountain. In addition to the serious damage to the old village, the new site is closer to the mountain, which is easier to defend and difficult to attack. The newly built Hengyuan Fort is located on the high platform on the west bank of the Wenjing River, which is close to the majestic mountain in the north, only a few dozen meters away from the mountain pass, and close to the surging river in the west. The enemy had to attack the walls from the east and south, so the Thunderbolts not only designed the east and south walls to be wider and thicker, but also reinforced them with steel bars in key areas.

According to the design plan, Yokohara Castle is also divided into an inner castle and an outer castle, but it is not a traditional square shape, but it has been improved by combining the advantages of the fortress and designed as a hexagonal shape. The outer city wall is 200 meters long on each side, with a total length of 1,200 meters, a wall height of 9 meters, and an average thickness of 6 meters at the bottom and 4 meters at the top; The inner wall is 60 meters on each side, 6 meters wide at the bottom and 4 meters wide at the top, but the wall is 3 meters higher than the outer city wall and reaches 12 meters. The foundations of the inner and outer walls were dug several meters deep before being backfilled with stones and tamped, and then paved with strips of stones, while the walls were poured from cement concrete into a one-meter-thick frame, and the interior was filled with rammed earth. In fact, if the city wall is poured into cement concrete, it will definitely be stronger, but the cement production capacity of the Perak Army simply cannot meet such a large amount of work. Even according to the current design scheme, the cement inventory of the industrial company in the early months plus the full production during this period is barely enough. Not only is the consumption of cement and stone huge, but the demand for steel is also very amazing, and the steel required for the city gate alone is thousands of catties. The outer city has four city gates in the southeast, northwest and northwest, and the inner city has only two city gates of the north gate and the south gate, these city gates are all wrapped by iron plates and thick wood, each door is more than 1,000 catties, especially the two gates in the southeast weigh more than 1,000 catties of iron plates alone, and more than 10 people need to use a winch to pull open.

Yokohara Fort also did not have traditional fortifications such as arrow towers, horse faces, and urn castles, but only a drawbridge was set up to cross the moat. In fact, this moat was only a by-product of fortification, ramming the city wall and other sand and earth excavation projects, but because it became bigger and bigger, it simply expanded into a moat 20 meters wide and 5 meters deep. It is better to say that it is a moat than a moat, because the design of Yokohara Fort was deliberately located on a high platform with flood control considerations in mind, so it was impossible to draw water into the moat. The most important thing that distinguishes Yokohara Fort from the traditional castle is the addition of an additional roof on the city wall, which is an important experience for the Perak army to use the artillery at the head of the glazed dam and the wall of Wanjiabao. The Perak Army found that artillery, as the most important weapon for defending the city, was not only vulnerable to the enemy's priority attack, but also afraid of bad weather such as rain, so in the design plan, the front chest wall and cement frame roof were built on the inner and outer city walls to shield from rain and to prevent the enemy's arrows and siege equipment.

The foreign aid channel in the defense of the city was crucial, and Yokohara Fort designed two supply channels. All the way is the waterway supply channel, out of the west gate of the fortress and walk down the river embankment more than ten meters is the wharf, the Wenjing River out of the mountain forms a river bay here, the river surface is wide and the water flow is gentle, not only suitable for transport ships and even the naval warships also have room for maneuver, so a wharf is built at the same time as the fort is built. It's just that the mountain river section upstream of the wharf, the water is turbulent and rocky, and it is impossible to sail at all, and the boats can only trace the water from the downstream. The other supply route is the mountain road leading to Wanjiaping, which is only a few dozen meters away from the mountain pass, and the artillery on the city wall can easily destroy the enemy trying to block the mountain pass, so the probability of being cut off is extremely low. However, in order to be sure, a hidden tunnel was designed from the fort to the pass, so that the enemy who tried to block the pass could be attacked from behind.