After confirming that the Zhou army really withdrew its troops, rather than feinting to retreat and attack and intending to kill himself, Cao Jiyun left some of his cronies to continue to closely monitor the movements of the Zhou army and monitor the defenders in the city, and on the other hand, he led other henchmen and personal soldiers back to the former Gu'an County Ya, which he had regarded as a temporary Chinese military tent, and began to write urgent letters to his boss, Xiao Siwen, who was left behind in Nanjing.

In this emergency rescue letter, Cao Jiyun not only told about the siege of the Zhou army that day, but also explained some of his experiences with the Zhou army's firearms. He said that although the firearms of the Zhou army were sharp, they would inflict great casualties on their opponents -- as can be seen from the fact that there were only 18 explosions on the head of Fangcai City, but the Liao army suffered nearly 100 casualties. However, there also seem to be some limitations and deficiencies in the use of firearms by the Zhou army.

First, the Zhou military firearms seem to have harsh requirements for the weather, and it is estimated that they can only play a role when the weather is fine, and once it encounters a rainy day like today, it will have a lot of inconvenience in use. According to the soldiers with outstanding eyesight, only six weapons called artillery by the Zhou army really attacked the city, and the other 30 or so artillery pieces suddenly stopped not long after they began to be placed and prepared, and then they were re-dismantled, loaded, and withdrawn to the Zhou army camp together with the Zhou army's foot soldiers. Judging from the fact that the Zhou army attacked the head of the city 18 times with firearms today, causing nearly 100 casualties to the defenders, if the more than 30 artillery pieces were also used at the same time, then even if one artillery only attacked three times, the casualties to the defenders at the head of the city would be at least 4 or 500 people. In this way, if the more than 30 artillery pieces of the Zhou army attack the city together, it will not be too much, only ten attacks per block, then the defenders on their side on the city will only be left. But what is strange is that the Zhou army has such sharp weapons in its hands, but only uses one-sixth of them to carry out a few tentative attacks, and the other five-sixths of the artillery is loaded and dismantled, and the troops are collected and returned to the camp under the situation that their own side has an absolute advantage -- you must know that returning to the camp under such circumstances will not only affect the morale of the Zhou soldiers, but also increase the fighting spirit of the Liao defenders.

After carefully analyzing the various circumstances and factors at that time, Cao Jiyun came to a conclusion that even he found surprising - the main reason why the Zhou army stopped attacking the city was the weather, and the rain falling from the sky seriously affected the use of firearms by the Zhou army, so that it had to withdraw its troops and camp after making several symbolic attacks on the head of Gu'an as if demonstrating. In other words, Zhou's firearms could not be used normally on a rainy day—at least not to their full potential. If the Liao army could skillfully arrange and use its cavalry superiority to carry out a surprise attack on the Zhou army on a rainy day, it was very likely to destroy its proud "Shenji Army" in one fell swoop. In that case, it can not only reverse the decline of the Liao army since the start of the war, but also deal a heavy blow to the morale of the Zhou army, which can be described as killing two birds with one stone.

Second, although the firearms of the Zhou army were powerful, they were complex to operate and slow to attack. It took dozens of sergeants a whole cup of tea to place a cannon. Based on the calculation of the 36 artillery pieces of the Zhou army, at least 2,000 people are needed to operate. And there are by no means so many soldiers in the Zhou army's artillery array today. Therefore, Cao Jiyun guessed that the Zhou army was usually equipped with many fewer sergeants per artillery than today. In other words, the speed at which each gun is placed in normal times is naturally much slower than today. And today it takes a cup of tea to place an artillery, so wouldn't it take a meal or even longer to place an artillery piece in peacetime. If this is the case, then as long as the Liao army can seize the favorable opportunity and send elite cavalry to attack the Zhou army's array while the Zhou army has just begun to deploy artillery, it can avoid the attack of the Zhou army's artillery and pull the battle back to the familiar mode of the Liao army. Under this traditional model, the Liao army, which has the advantage of cavalry, will occupy the initiative on the battlefield in most cases.

Moreover, even if the Liao army could not take advantage of the Zhou army's artillery to attack, in the face of the rushing cavalry, with the attack speed of the Zhou army's artillery today, even if the two sides were one or two miles away, they would probably have at most one chance to attack, and then they would become the target of the Liao army's cavalry -- even if the opponent's artillery was protected by infantry troops, this return to the traditional cavalry and infantry combat mode was still very beneficial to the cavalry-based Liao army. Even if the Liao army can't win a hundred battles, it will at least be able to kill an evenly matched opponent with the other side, and will not repeat the mistake of the Han army's defeat under the Dabao garrison -- the power of the Zhou army's artillery today finally made Cao Jiyun understand the reason why the Han army led by the "Liu Invincible" Liu Jiye (Yang Ye) was defeated by the opponent's artillery before he even saw the enemy's face. In his opinion, if it weren't for the extremely limited number of artillery attacks of the Zhou army today, and he took the lead and ordered a group of personal soldiers to line up at the head of the city, he was afraid that the infantry defending the city would have been scattered by the Zhou army's artillery - after all, if he hadn't heard that the Zhou army had such powerful firearms before, Cao Jiyun himself might have regarded the huge explosion of artillery attacks as heavenly thunder and as God's punishment for himself, and because of this, his heart and guts would have been broken, and he would never have a trace of fighting spirit again. ,

It is based on the above two analysis results that Cao Jiyun repeatedly implored his boss to send troops immediately in the letter of request for help sent to Xiao Siwen, taking advantage of the bad weather and successive rains in the past few days, and the opportunity when the firearms of the Zhou army could not play their role very well, to annihilate the vanguard of the Zhou army under Gu'an City and cut off one of Chai Rong's arms. At that time, even if the Zhou army could not be made to retreat and lose the help of the sharp firearms of the "Shenji Army", its strength would be greatly reduced, and it would be at a disadvantage in the confrontation between the two armies.

I don't know if it was the defects of the Later Zhou "Shenji Army" written by Cao Jiyun in his letter asking for help that enhanced Xiao Siwen's courage to fight with the Zhou army, or at least the courage to fight with the "Shenji Army", or whether the main force of the Later Zhou army that was increasingly approaching Youzhou City made him feel restless, and in order to give an explanation to the Liao Emperor who would arrive soon, he had to take the main force of the Liao army in Youyun area away from Youzhou City and run into the Zhou army of the Northern Expedition, so as not to fall into the charge of being afraid of war and failing to block the enemy. On the day he received Cao Jiyun's letter asking for help, Xiao Siwen ordered the Youyun Liao army stationed in and around Youzhou City to prepare as quickly as possible, and the next day he personally led 60,000 of them (50,000 Khitan cavalry and 10,000 local villagers) to set off south to meet with Chai Rong, the son of heaven who vowed to recapture the sixteen states of Youyun.

Of course, while Xiao Siwen led his troops south, he did not relax his defense of Youzhou City. On the basis of leaving behind 20,000 defenders -- 10,000 Khitan regular troops and 10,000 local villagers -- he transferred 20,000 villagers from neighboring prefectures and counties to defend to the death with nearly 40,000 horses.

When Xiao Siwen agreed to send reinforcements, and when the reply letter to the rescue was handed over to Cao Jiyun under his own command, Cao Jiyun, who was originally afraid that his boss would not dare to go south to reinforce him because of the fear of war, finally breathed a sigh of relief, and the heart that had been hanging was finally let go at this time. On the one hand, he used a new defensive strategy to arrange for the defenders of the Gu'an Army to strictly defend the city, and on the other hand, he constantly sent people to inquire about the situation of Xiao Siwen's reinforcements going south, and made a determination that he must firmly hold Gu'an City until his own reinforcements arrived.

At the same time that Xiao Siwen dispatched troops and led the main force of the Youyun Liao Army to leave Youzhou City and go straight to Gu'an County, which was hundreds of miles away, the crossing team committee of the "Liangyuan" also received news from the "Dark Feather" Youzhou Branch about the main force of the Youyun Liao Army. After receiving the long-awaited news, the crossing team that took the main force of the Youyun Liao Army from Youzhou City and prepared to go south for a decisive battle with the Zhou army as the best time for their own uprising, immediately convened an enlarged meeting of the committee, preparing to finalize the implementation of the "Jihua Operation Jihua No. 1" jointly formulated by the Ministry of Military Affairs and the committee.