After the Kudu cavalry rushed back to Chengdu, although the morale of the Mongol army was boosted for a short time, the Perak army significantly increased the intensity of artillery bombardment in the following days, and the morale of the Mongol army fell to the bottom again. Even the ordinary Mongolian soldiers in the city knew that these more than 1,000 cavalry obviously could not change the situation of being passively beaten, let alone turn the tide of the battle. At present, Genting City has fallen into the hands of the Thunderbolt Army, and the cities and strongholds around Chengdu, such as Guangdu, Xindu, Wenjiang, and Pixian, have also planted the banner of the Thunderbolt Army. On the fifth day, Kuaima came with the news that the Mongolian troops from Tongchuan Prefecture, Puzhou and Zizhou could not come to help, which made Liu Heima make up his mind to give up Chengdu. Kublai Khan first purged the Ali Buge forces in the Sichuan Mongolian army, and then sent a large number of cavalry to the north, which not only seriously weakened the combat strength of the Sichuan Mongolian army, but also made the Mongolian generals panic and suspicious of each other. In this eventful season, they all tried to protect themselves, and they all found reasons to refuse Liu Heima's request for help.

"Thirty-six strategies, go for the best policy". On the night of the tenth day after the siege, Liu Heima led his army to sneak out of the east gate by starlight and headed for Jianzhou. The 3,000 infantry troops who accompanied him this time were all lightly armed, and in addition to their weapons, they only carried ten days' worth of water, so they marched thirty miles in one night. After dawn, the cavalry of Kudu also left the city and went straight to Jianzhou, and Liu Heima gave him the task of blocking the pursuit of the cavalry of the Thunderbolt army. After Liu Heima and Kudu fled, there were only about 1,600 defenders left in the city, and in order to confuse the Thunderbolt army, the Mongol army asked a large number of people to wear the clothes of the new annex army to strengthen their momentum. The 5,000 defenders of Chengdu City suffered only three or four hundred casualties under artillery fire during this period, and the losses were not serious.

Among the 3,000 infantry troops taken away by Liu Heima, except for the Mongol and Han troops directly under him, the rest were all selected new elite troops. In order to prevent the escape from becoming a rout, and in order for someone to stay in the city and continue to attract the artillery fire of the Thunderbolt army, Liu Heima first promoted two new annex generals to serve as city guards and deputy city guards respectively, and then lied that there would be strong reinforcements coming, and he would lead the elite to converge, and defeat the Thunderbolt army in one fell swoop after the combined army. Although Liu Heima was not as tyrannical as the Mongolian generals, he was never polite to the new annexed army that violated the military order, and he had to lead Liu Heima to pick up the remaining old and weak soldiers to defend the city.

Although Liu Heima did things secretly, there was still a lot of movement among thousands of people out of the city, and they could hide from the eyes of the Thunderbolt army. After dawn, Ouyang Zhen sent scout cavalry to follow behind the Kudu cavalry, but the Mongolian cavalry was skilled in bow and horse, and the scout cavalry of the Thunderbolt army could not get close at all, so they had to go to a high place to watch from a distance with binoculars. Ouyang Xuan was also helpless about Liu Heima's escape, after all, the cavalry of the Thunderbolt Army could not break through the interception of the cavalry of the Kudu Division. If you want to use infantry to pursue, it is even more embarrassing, if you carry heavy artillery, you will not be able to catch up with the enemy who flees lightly, and if you do not carry heavy artillery, it will be difficult to defeat the enemy and even be bitten back, after all, it is 3,000 elite infantry and more than 1,000 cavalry. However, the two infantry brigades of the field division only had 3,000 people, and the number of more than 800 cavalry who were greatly injured was still less than that of the Mongolian army. Based on the above reasons, Ouyang Xuan sent someone to Huang Dagen of Genting City, asking him to defend Genting City instead of taking risks.

Ouyang Xuan always remembered the great man's words: "Strategically despise the opponent, tactically attach importance to the opponent". Although the Thunderbolt Army and the Mongolian Army were both dominant in battle, it must also be admitted that the Mongolian Army was the pinnacle of the combat power of the Cold Weapon Army. Therefore, he has always been very cautious in fighting against the Mongol army, because with the size of the Mongol army, it can fail many times, and the Thunderbolt army cannot afford to lose a major defeat at all, because it will bring an existential crisis and even mean a catastrophe. Ouyang Xuan's caution became the tranquility before the snowstorm in Liu Heima's eyes, in his opinion, the Thunderbolt army in Chengdu City had tens of thousands of elites but did not chase after them, and there were nearly 10,000 soldiers and horses in Genting City, so they must be planning a bigger action, and immediately ordered his subordinates to speed up their escape to Jianzhou. Liu Heima regarded the basic militia of the Perak Army, which was responsible for logistics and baggage, as elite soldiers. In fact, although this is a miscalculation, there is one thing to say, the combat power of the basic militia of the Thunderbolt Army is no worse than that of the elite of the new annexed army.

As soon as Liu Heima and Kudu fled, the cavalry of the Thunderbolt army blocked the east gate, and the new annexed army in the city became a turtle in the urn. At the beginning, the generals of the new annexed army defending the city were still full of expectations that Liu Heima would bring reinforcements back. As time passed, instead of a trace of reinforcements, the shelling became more and more intense. The mood of the defenders of the city also changed from hope to disappointment and finally to despair, and they knew that they had become outcasts. In fact, Kudu once suggested to Liu Heima that the city of Chengdu be completely burned down, leaving no useful things for the Thunderbolt army, but Liu Heima vetoed it. As a Sinicized Khitan, Liu Heima's temperament is not as brutal as that of a barbarian from the grassland, such as Kudu. During his governance of Chengdu, he also recruited displaced people to open up wasteland and reclaim land, not blindly burning, killing and looting, which is also the reason why he disagreed with the secret Huoli and others and chose to take refuge in Kublai Khan. Of course, Liu Heima's refusal to set fire to the city was not a bodhisattva's heart, but that he needed to keep the city to attract the Thunderbolt army.

Not knowing the strength of the defenders, and in order to reduce casualties, the Perak army shelled for a few more days before sending a small force to launch a tentative assault from the collapsed wall. As the battle line went deeper into the city, there was no tragic street fighting as imagined, but the battle was as smooth as a hot knife cutting butter, so Ouyang Xuan ordered a centripetal assault from the four gates. At the beginning, the new annexed army in the city was still fiercely resisting, but after the loss of the most powerful new annexed troops such as the guard's personal soldiers and the warlords, the remaining old and weak soldiers could not resist the big killing weapons such as grenades and light artillery, so they threw down their weapons and surrendered. As for the general of the new annex army defending the city, he was also a bachelor, and he knew that he had done all the bad things with Liu Heima, so he wiped his neck with a knife.

Chengdu City has been slaughtered by the Mongolian army several times, and after the occupation of the Mongolian army, it only squeezed and did not produce, so this once a large city with a population of one million has become extremely depressed, and the huge city is full of ruined walls. After Liu Heima took charge of Chengdu, although he tried his best to recruit displaced people, the population of the city was only more than 20,000 people. These people are all yellow-skinned, thin, and unkempt, and their lives are obviously extremely difficult. Ouyang Xuan ordered Zan Wanshou to temporarily preside over the government affairs of Chengdu, first counting the population and then opening the warehouse to release grain, and in the process found out a lot of new soldiers hiding among the people, and the place where these people went was naturally a mine in the mountains. Zan Wanshou was disappointed after counting the treasury, not only did he have very little money and materials, but he also had not much food, so he couldn't hold on for a long time, and this was one of the reasons why Liu Heima abandoned the city and fled.

Before capturing Chengdu City, Ouyang Xuan received news from Huang Dagen that Liu Heima, and Hu Du had led their troops to Jianzhou. When passing through Genting City, the Mongol army also sent hundreds of men to make a tentative attack, but they were bombarded by the heavy fortresses at the head of the city, and suffered heavy casualties, so they had to flee in disgrace. At present, Huang Dagen has formed a temporary naval army of 500 people in Genting City, this naval army has more than 100 small boats, and small artillery is installed on the boats, although it cannot pose a threat to the Mongolian army in Jianzhou down the river, but it is enough to control the river from Jintang to Genting City, and prevent the Mongol army from crossing the river to attack Genting City.