After the winter, as the weather gets colder and colder, western Sichuan also enters the agricultural season. But at this time, the mountains under the rule of the Thunderbolt army were in full swing, and there was no idler. Young and strong laborers work in the reclamation of wasteland and in factories and mines, school-age children attend school, and women and the elderly do manual work such as spinning cloth and making shoes. All of them were making their own efforts to prepare for a possible Mongol invasion. In addition to working, the young and strong labor force also has to participate in the military training of the garrison battalion, and they are tired enough, but the intensity of their military training is much easier than that of the field battalion, which is close to the actual combat training. In line with the principle of "sweating more in peacetime and less bloodshed in wartime" as Xuan Ge'er said, Cao Ergou carried out marching training over mountains and mountains in the field camp at every turn, or carried out wilderness survival training in the deep mountains. This harsh training method made the soldiers complain bitterly, and secretly called him "Cao Devil".

Just like the historical trajectory in Ouyang Xuan's memory, before the winter, the marshal of the Mongolian army, Atahu, had already arrived in Chengdu. After Liu Heima and Atahu joined forces, the Mongols immediately began a large-scale siege of the city and plundered the land. Unlike before, the Mongol army did not blindly burn, kill and loot to create a no-man's land to destroy the war potential of the Southern Song Dynasty, but adopted a combination of political and military means to coerce the Song army to surrender by brutally slaughtering the city. This form of warfare seemed to be much milder, but in fact it was a greater threat to the Southern Song regime. After the slaughter of several prefectures and counties, the will to resist of the Southern Song Dynasty officials and troops collapsed, and most of the prefectures and counties in western Sichuan surrendered to the Mongols.

Of the four counties under the jurisdiction of Chongqing Prefecture, Yongkang and Gangwon have surrendered to the Mongols. Xiong Ben was appointed by the Mongolian military to Yongkang County because of his possession of Yongkang City and Hengyuan Village. Jinyuan County, where Chongqing Mansion is located, has been abandoned by Pan because there is no danger to defend, and he moved the population and army to the subordinate Xinjin County's naval army village. Xinjin Village is surrounded by water on three sides, easy to defend and difficult to attack, and there are hundreds of large and small warships, which is a difficult bone for the Mongols who have no naval army. The danger was not the main reason why Pan was reluctant to surrender, nor was it because most of his relatives were in Lin'an, but because he felt that the Mongol army's remuneration for keeping him in his original position was too low. At present, the situation that most of the surrounding and adjacent areas of the Thunderbolt Army have surrendered to Mongolia is definitely not a good thing for the Thunderbolt Army. The Mongols controlled nearby prefectures and counties, which greatly limited the space for the Thunderbolts to operate and made it more difficult to obtain vital supplies and intelligence.

However, even if everyone surrendered, Ouyang Xuan would never surrender. Of course, the Thunderbolt army was also fully prepared, and even if the Mongol army also attacked, they were confident that they would be able to repel the attacking enemy, because the biggest defense in the mountains, Wanjiabao, was completed. This fort built at the T-junction of Wanjiaping is a square castle, it is built according to the terrain of the mountain, one side is against the mountain and the other side is facing the river, the road leading to Wanjiaping and to Liuliba is completely blocked, and it is necessary to pass through the fort to lead to the two places. In terms of defense, this fort is absolutely a one-man pass, ten thousand people can not open, its fort wall is about ten meters high and up to three meters thick, the foundation is paved with wide stones, and the steep and straight wall is made of concrete. To enhance the damage resistance, the front wall is also cast with thumb-thick steel bars as the skeleton. Although due to the topography, Wanjiabao did not have parapets and trenches, the fort gate was reinforced with thin steel plates as armor, which was extremely thick and solid. During the acceptance of the fortress, Ouyang Xuan had ordered people to bombard it at close range with a light mother and son cannon, and after three shotguns in a row, the gate of the fortress was unscathed, only shallow dents were left on the armor steel plates.

Wanjiabao is easy to defend and difficult to attack, and because the road into the mountain is narrow. Although the Thunderbolt army widened the road into the mountain after capturing Wanjiaping, it was still unable to pass through the large siege engines. And the light equipment that the enemy barely brought into the mountain could not cause damage to the concrete walls. Moreover, because the attack surface is too narrow, the enemy army cannot use the tactic of crowds to swarm up, so it can only use the tactic of adding fuel. For the defenders of Wanjiabao, it was simply the enemy taking the initiative to send credit and heads. You know, as long as the enemy army appeared in the open space in front of Wanjiabao, they were completely exposed to the artillery fire on the fortress. The Thunderbolts installed rapid-fire sub-cannons on the city walls and on the two turrets behind the walls, and the non-stop firepower that a total of twelve guns could form was an absolute nightmare for any attacker. Cao Ergou patted his chest for this and assured Ouyang Xuan that a company stationed in Wanjiabao could block the attack of the enemy's 10,000 people.

The first intrusion into the nuisance was a 20-man Mongol reconnaissance team. They set out from Hengyuan Village and went all the way into the mountains until Wanjiaping, but they did not encounter resistance along the way. Just when I expected that this reconnaissance operation would go as smoothly as a trip, I encountered an impregnable wall. As soon as they turned the corner, they saw that the tall fortress in front of them had blocked the way forward. Seeing that they could not advance, the Mongol soldiers fired a few rounds of arrows into the fortress to vent their anger and then retreated out of the mountain.

The second attack of the Mongolian army was a hundred-man team, and this Mongolian army was strict and extremely arrogant. The Mongols expected that the officers and soldiers here were as cowardly as the plains, and that they should either have fled from the wind or should have knelt down in front of them and surrendered. Seeing that the gates of the fortress were closed, and that the guards at the head of the wall did not heed their shouts, the leading Mongol officer, in a fit of rage, ordered an attack. After the Mongols dismounted, some of them pressed the wall with bows and arrows, and some of them rushed to the fortress wall with swords and shields and screamed wildly, and threw iron hooks with ropes to hang on the wall. The Mongols climbed along the ropes, but were thrown with spears and stones by the Thunderbolt soldiers at the top of the wall, and they fell to the ground, and the archers behind were blown to pieces by the grenades thrown from the walls. In just one turn, the Mongols lost more than 30 men, the battle damage rate reached an astonishing one-third, and the centurion who led the charge was also stoned to death.

The death of the centurion of the Mongolian army was like the last straw that crushed the camel, directly causing the Mongolian army, which had always been known for its strict military discipline, to break up directly, leaving behind more than ten corpses and more than 20 wounded, regardless of the desperate escape out of the mountain. To say that the Mongols' combat strength was not so unbearable, and their defeat was so miserable, it was because of their arrogance and direct ignorance of the tall fortress, and they did not expect that the Shu people would still be so bloody after being slaughtered repeatedly. The corpses of the Mongolian soldiers who died in the battle were carried and buried by the mountain people in a scramble to bury them, and this is the time of winter fertilizer, which is an excellent fertilizer. The wounded of the Mongolian army were not incorporated into labor camps, but were driven out of the mountains. The reason for this was to allow the wounded to drain the resources of the Mongolian army and disrupt the morale of the army, and one wounded often needed two or three people to take care of them. Of course, before they were released, the wounded Mongol soldiers had their right fingers cut off to prevent them from opening their bows and arrows after being wounded.

Only three Thunderbolts were shot in this battle, one of whom was seriously wounded by an arrow in the face and two others suffered minor arrow wounds in the arm. For this reason, Shi Zhongshu, the commander of the first company of the field battalion guarding the fortress, was severely reprimanded by Cao Ergou. In Cao Ergou's view, the Perak soldiers were wearing rattan armor and protected by arrows and shields, and the Mongolian army could still injure three people in one round of attacks, which was really an improper command. The reason why Ishiakaki was reprimanded was also because he recklessly used a grenade. According to Ouyang Xuan's requirement not to expose his strength too early, the Thunderbolt Army is currently trying not to use firearms, so as not to make targeted preparations in advance. Since the invention of firearms in the Northern Song Dynasty, they have been gradually used in wars, and the Mongolian army has gradually learned how to deal with it after suffering many losses in the battles with the Jin army and the Song army. Although the firearms of the Perak army were far more powerful than those of the Jin and Song armies, they were not inexplicable, not to mention the restraint methods such as rainy battles and cavalry raids, and civil fortifications and iron shields could also greatly reduce the power of firearms. You must know that the Mongol army is invincible, in addition to its strong military value, but also because of its strong ability to learn and adapt to war.