"Born Chongqing, iron Luzhou", Shenjian City is like Hezhou Diaoyu City, the terrain is dangerous to be surrounded by solid water, choke the Yangtze River to lock the waterway, the mountain is a city, the city is a mountain, extremely easy to defend and difficult to attack. Meng Ge besieged Diaoyu City in vain, and Yu Xing led an army to besiege Shenjian City, which was also difficult. At the beginning of July, Yu Xing led the army to occupy the Yellow City on the other side of the Yangtze River in the south of Shenjian Mountain, blocked the water traffic by virtue of the superiority of the naval army, and ordered the capital commander Zhang Gui and Jin Wende to garrison the mouse pass to block the Mongolian army from the direction of Jian and Zizhou. Liu Cheng was extremely arrogant, and in the face of the siege of the Song army, he took the initiative to attack from the water, but was unexpectedly defeated by Yu Xing with his superiority in strength. After suffering a big loss, he had to change his tactics and retreat in the city, waiting for Niu Lin to send reinforcements to rescue.

Yu Xing knew that if he couldn't win quickly, when the Mongolian reinforcements arrived, he would inevitably fall into the dilemma of being attacked from both sides, repeating the mistake of Pu Ze, so he forced his subordinates to attack Shenjian City day and night. Under the onslaught of the Song army's officers and soldiers, regardless of casualties, the weak Shenjian City almost fell. Seeing that the situation was not good, Liu Quan distributed all his family property to the soldiers. Liu Yuanzhen, the son of Liu Heima, was also in the city of Shenjian at this time, and in order to express his determination to live and die with the city, he ordered people to slaughter himself and his horses to reward the defenders of the city. The two of them took the lead in ascending the east gate to fight to the death with the Song army, and the defenders saw that the commander was so demoralized that they slowly stabilized the defensive line. On the other hand, the Song army could not attack for a long time, suffered heavy casualties, its morale was declining day by day, and the offensive was becoming more and more weak. In desperation, Yu Xing had to give up his plan to attack quickly.

Just as Yu Xing was attacking Shenjian City, the Thunderbolt Army also began a large-scale mobilization. On the waterway of the Minjiang River, large and small ships went downstream, and the docks of the Jiading City Navy were full of gunboats, and the main warships alone exceeded 30. The side portholes of these main warships were tightly closed, and it was not clear that the guns inside were clear, but just by the draft of the ships and the number of portholes, it was known that these warships were armed with at least twenty or thirty guns. In addition to the artillery ships, there were at least a hundred ships of various types on the docks, many of which had shiny ramming angles and armor in the bow, apparently used to charge into battle. Of course, there are more auxiliary vessels, especially transport ships, which are in the hundreds.

While the naval army was massively massing towards Jiading, the land forces of the Perak Army were retreating. The Thunderbolt Army, which confronted the new annexed army on the Mianshui front, was suddenly reduced by two-thirds, and the long front was only more than 1,000 people, which made Yang Wen'an, who was beaten to the ground by artillery, have the urge to attack again. The number of Thunderbolts in the direction of Genting City and Jintang was also greatly reduced, and the defenders of Genting City were even reduced to 500 people, and the Jintang garrison was also reduced by less than 1,000 people. In addition to these two strategic directions, the number of Thunderbolts in the rest of the border with the Mongol army has been reduced by a third or even more than half. In view of this situation, Liu Heima, Niu Ling, and Baijianu judged that the Thunderbolt army either had no intention of starting a war, or was preparing to transfer to the direction of Luzhou by water.

In fact, the Thunderbolt army made such a move to make the Mongolian army come to such a conclusion. The internal discord of the Song army in Sichuan is well known, and some time ago, the Thunderbolt army's refusal to send officials from Lin'an and Yu Xing's seizure of the Nanyang Company's fleet caused a stir. It can be inferred from common sense that the Thunderbolt Army retreated at this moment to put on a posture of watching the fire from the other side. Even if the Thunderbolt army wanted to go out, it also avoided its place to show off its strengths, taking advantage of the abundant river season in July, with the naval army as the forerunner and Yu Xing's joint forces to attack Luzhou, which was evidenced by the dense sailors moored outside the city of Jiading.

The expedited cavalry from Kaiping sent back an order from Kublai Khan himself, and he asked to send troops to rescue Liu Quan. This is not only because Liu Quan is a fierce general, not only because the geographical location of Tongchuan Road and Luzhou is extremely important, but also because Kublai Khan listened to the advice of Lian Xixian and other advisers and asked for a thousand dollars to buy horse bones. Saving Liu Quan at any cost was to tell other Southern Song generals that as long as they defected to the Mongol army, they would not be disappointed, and this gesture was extremely important for Kublai Khan, who was determined to dominate the world and become the Khan of Heaven. After receiving the order, Niu Lin did not dare to be careless, and immediately pulled out troops to the rescue of Shenjian City, and sent 2,000 cavalry led by Lida as the vanguard. Liu Heima and Baijia Nu stayed in the rear and prepared for the grain and grass baggage.

Niu Ling led 10,000 people to Luzhou by land and water, and the movement was naturally not small, and he was detected by the intelligence officers of the Thunderbolt Army as soon as he set off. Unlike Newland's judgment that the Thunderbolts would watch the fire from the other side, the Thunderbolts were preparing to attack at this time. The previous contraction was just like the punch before the punch was accumulated, in order to strike harder. At present, the equipment of the Thunderbolt army has reached more than 90 percent, and the number of war horses has reached more than 8,000, which is not far from the ideal state. It's just that Ouyang Xuan still ordered all units except the Third Division to train on the spot, on the one hand, to further strengthen training and reserve more weapons and ammunition, and on the other hand, to paralyze the Mongolian army, so that they can relax their vigilance and focus all their attention on the direction of Shenjian City.

For the time being, there is a reason why it is inconvenient to say. In order for the Perak army to continue to grow in strength, it must need more geographical space, but these regions obviously cannot be taken from the Song army, but only from the Mongolian army. If the Thunderbolt army did not hesitate to suffer casualties and troops to reach Luzhou, it would not be difficult to take the Shenjian City, but the result would definitely be a wedding dress for Yu Xing and other corrupt officials. After they defeated Liu Chuan and the Mongolian army, they would only desperately squeeze the people and loot the people's fat and ointment, and the people of Tongchuan Fulu would still live in dire straits. Ouyang Xuan's decision was to wait for Niu Xuan to go east along the Tuojiang River to Luzhou, attack the rear of the Mongolian army, cut off its grain and grass, and force it to return to help. If the Mongols did not return and held the Divine Arm City, the Thunderbolts would follow the pursuit and encircle it by land and water, and under strong firepower, they would definitely be able to recapture it from the Mongols.

The successful implementation of this plan required strategic deception, i.e., to convince the Mongols that the Thunderbolts would not attack by land, but would attack by water, using the advantage of their gunboats. The ships docked at the dock of the Jiading Navy were for the Mongolian spies to see. In order to let the Mongolian spies see more clearly, Zan Wanshou also specially chose to load the ship during the day, and after being ready, it took a few days before he went to Xuzhou downstream in a hurry. The goal given by the General Staff to the Third Division was to seize Xuzhou and its subordinate counties and then go downstream, and not to rush to attack Shenjian City, but to first open the road to the Chishui River and get in touch with Banzhou. After joining forces with the Banshu army, wait for the opportunity to attack Shenjian Castle.

In addition to the 3rd Division under his command, Zan Wanshou also strengthened the three battalions of the 1st Division and the 2nd Division, and the number of regular troops alone reached 9,000, plus the 5,000 basic militia in charge of logistics and baggage troops, the total number reached 14,000. There were simply not enough ships to carry so many people, so Zan Wanshou had to order the army to advance by land and water. Along the waterway were two naval brigades, with more than 200 large and small warships escorting hundreds of heavy ships down the river. The land troops consisted of four brigades of 6,000 infantry cavalry and 5,000 basic militiamen, and they went straight to Xuzhou along the west bank of the Minjiang River.