The sudden deterioration of the situation began at the end of April. After Niu Ling led the army to reinforce Chengdu, the Mongolian army gained momentum, and the balance of the battlefield gradually tilted to the side of Mongolia. Pu Zezhi organized several major offensives in a row, but they were all repelled by the Mongol army. Immediately afterwards, Wang Dechen led 5,000 elite cavalry of the Mongolian Lizhou garrison to rush to help, which made the Song army even more disadvantaged. After the Mongol army occupied the initiative on the battlefield, it continued to storm the Song army camp, but under the obstruction of trenches and fences, the cavalry advantage could not be brought into play. Although the Song army was exhausted by the fight, it was unable to break through the camp in a hurry, and it did not take much advantage. Seeing that the strong attack could not be achieved, Niu Xuan adopted Liu Heima's strategy, sent troops to harass the grain routes of the Song army, and sent a large number of rangers to plunder the countryside of Zhou County, using a scorched earth policy to weaken the Song army's supply and war potential. Under the wanton capture of the Mongol army, the Song army had no choice but to retreat in the cities of the state capital and county, allowing a large number of dock forts and stockades in the countryside to be breached, property and grain were plundered, a large number of houses were burned, the people were either killed or plundered into slavery, and the rest fled in all directions.

People fled in the same direction as on previous occasions, with most of them seeking refuge in nearby counties. This time, the government accepted the refugees into the city, in addition to the reason why Pu Ze gave the order, but also because of the serious lack of population in the cities of western Sichuan after Liu Heima's invasion of Chengdu, and more importantly, there was about half a month before the wheat was ripe and the summer harvest was made. Labor is needed for the harvest, and the harvested food is surplus for the refugees in addition to military supplies. A small number of well-off people took boats in the direction of Jiading and Chongqing, while some refugees fled to the mountains. For a time, a large number of refugees poured into the mountainous areas of western Sichuan prefectures, such as Peng, Qiong, Mian and Chongqing. Among them, due to the propaganda during the reconnaissance operation in the early stage, the mountainous area northwest of Chongqing Province, which was controlled by the Thunderbolt Army, had the largest influx of refugees, with more than 20,000 refugees. In addition to the resettlement of these refugees in Jiguan Mountain, some of them were resettled in Wugen Mountain, Meihuazhai and other places under the rule of the Perak Army. Fortunately, the climate was warm at this time, and there was no shortage of wild vegetables and fruits, plus the relief food of the Thunderbolt Army, although the refugees could not eat well, they could still live.

It was not only the refugees who fled to the Thunderbolts, but even a 200-strong rout. After Pu Zezhi's counterattack on Chengdu, the Mongol cavalry stationed in Qingcheng County, Daojiang County and Guankou Village to the east of Yongkang City retreated to Chengdu one after another, leaving only the new annex army to garrison. When Yao Shi'an of Genting City learned of the retreat of the Mongol army, he ordered his henchman Lin De, stationed in Pengzhou, to recover these three places in order to expand his territory. The new annexed army in these three places was originally the Song army, and its combat effectiveness and will to fight were very weak, and when they saw that Lin De led the army to attack, they surrendered again. In a time, Linde's men expanded from 500 to 3,000. The growth of strength also brought about the expansion of ambitions, and Lin De's orders to Yao Shi'an also became disobedient, not only refusing to select the elite to Genting City, but also not sending money and food to Pu Zezhi's military camp. The three places he possessed were the defunct Yongkang Army. The army in the two Song Dynasty was a military and political institution at the same level as the state and government, and was often set up in important military places. In this troubled era, strength is king, and with his strength, he can be a warlord who divides one side. He has lived tremblingly under the mean and unkind Yao Shi'an for a long time, and he is really fed up with these days of relying on people's noses.

It's just that Linde didn't get complacent for long, and after the Mongols occupied the battlefield advantage, they sent personnel to plunder the prefectures and counties, and as a result, the two counties of Qingcheng and Daojiang surrendered to him, and the Mongols were surrendered. In fact, Lin De was not unguarded against these capricious surrenders, and after he took possession of three places, he sent his henchmen to lead a hundred elite troops to garrison the two cities to monitor and suppress the newly annexed new annexed army. The 500 people under his command are the elite troops of the Song army in Yunding City, and their combat power is much stronger than the surrendered troops in Qingcheng and Daojiang counties. Therefore, these surrenderers were not treated equally, but were wantonly insulted and robbed of their property. Lin De didn't care about this, because the same was true within the Song army in Genting City, and the soldiers were also divided into three, six, nine and so on. It's just that what he didn't expect was that although these rebels were scumbags of war and were as timid as rats in front of the Mongolian cavalry, they were as fierce as tigers when they killed their own people. As soon as the Mongol cavalry persuaded the two cities of Qingcheng and Daojiang to surrender, they killed Linde's henchmen and surrendered.

"It's not that you can't betray, but it depends on how big the interests are." If the price is right, Linde is also willing to surrender to the Mongols. Therefore, when a Mongol hundred-man team persuaded him to surrender under the Guankou village, he was moved to surrender and prepared to send an envoy to negotiate with the Mongols. Now there are still 1,000 troops in Guankou Village, and according to the Mongol recruitment standards, he can obtain the official position of Zhixian, which is not much different from his rank in the Song army. Although in the Song Dynasty system, the magistrate belonged to the civil official, which was much higher than the military attache of the same rank, but Lin De was not satisfied, he wanted the location of the governor of Pengzhou, and wanted the Mongols to return the territory and men of Qingcheng and Daojiang counties to him.

The reason why Linde had such confidence to negotiate terms with the Mongols was that he still had 300 direct subordinates, and the remaining 700 were also selected by the newly annexed army. It's a pity that this stockade is too small, and the garrison of 1,000 people is the limit, otherwise Linde will personally lead more men and horses. Guankou Village was originally the military village of the Yongkang Army, and the defense facilities were much more complete than the two cities of Qingcheng and Daojiang, which were ruined by the city defense, and the Mongols had to pay heavy casualties if they wanted to take here, which was also the reason why they chose his garrison here. Linde's confidence comes from the special geographical location of Guankou Village, which is surrounded by mountains and rivers, and next to the village is the Dujiangyan Water Conservancy Project built by Li Bing and his son, which not only tightly chokes the northern line of the ancient tea horse road leading to Wei and Mao in the West Sichuan Plain, but also chokes the water conservancy lifeline of millions of acres of land in the West Sichuan Plain, and its importance is self-evident. In Linde's opinion, the Mongols did not suffer a loss by exchanging the position of a governor for such an important place.

The envoys sent by Linde to negotiate with the Mongols had not yet left the village, and the surrendering troops who did not play their cards according to common sense mutinied again. Seeing that the Mongols were persuaded to surrender outside the city, but Linde was slow to respond, they really couldn't wait, on the one hand, they were afraid that the Mongols would attack and slaughter the city, and on the other hand, they also needed Linde's head as a vote for surrendering to the Mongols. To say that Lin De is defending the village with his 300 elites, he is not afraid of the Mongolian 100-man team outside the village, let alone the 700 mutinous soldiers. It's just that Linde was caught off guard and suffered from the enemy on his back, so he led the army to flee in a panic. Because he was afraid of Yao Shi'an and Pu Ze's punishment, and saw the propaganda leaflets of the Thunderbolt Army, Lin De, who was chased and killed, had no choice but to flee in the direction of Hengyuan Town. When he fled to Yongkang City, he counted the number of people, and there were still 200 people with him. Linde originally wanted to defend Yongkang City, but the city had already been moved by the Thunderbolt army, and the city defense facilities were dilapidated and empty, and he couldn't hold it at all due to lack of food and food. And his subordinates, fearing that the Mongols would chase them, clamored to go to the Cockscomb Mountain. Lin De had no choice but to go to Hengyuan Town with everyone, and was temporarily placed by the Thunderbolt Army in Wandanping, the deepest part of Jiguan Mountain.