After Zhu Yunwen became the prince, the biggest thing he planned was to build Suiyuan City, and in the end, although Suiyuan City was successfully built, it also paid a very heavy price. Hongwu Emperor Zhu Yuanzhang died early, Fu Youde, the Duke of Yingguo, died on the battlefield, King Ning was exiled to Yunnan, Wang Bi guarded Daning, King Zhou transferred elite troops to Daning to garrison, King Yan returned to Beiping to preside over the overall situation, Chen Xuan was stationed in Datong, and lost nearly 100,000 elite soldiers, which can be described as a heavy loss. In the end, although Zhu Yunwen built Suiyuan, it also allowed Zhu Di to obtain a better environment for rebellion, and he joined forces with the King of Zhou, so that Zhu Yunwen threw a mouse trap and did not dare to start easily, and finally Zhu Di rebelled blatantly, causing a catastrophe.

But Zhu Yunwen was not without gains, the grasslands near Suiyuan and the horse farms in Hetao provided excellent horses, knights and training grounds for the Guards Cavalry Army, and in the battle with Zhu Di, although the Guards Cavalry Army suffered heavy losses, it also made great contributions.

Another thing Zhu Yunwen did was to develop Liaodong. First of all, in Jinzhou, Liaodong, began to try out the tun angel, due to the good effect, Zhu Yunwen set up the Liaodong general tun angel in the first year of Jianwen; secondly, he gradually sent his henchmen Geng Xuan and Wu Sheng to control the Liaodong Metropolitan Division, and then successively dispatched martial arts students to Liaodong to strengthen the training of the Liaodong Army; In the end, Zhu Yunwen also changed his equipment one after another, such as tougher armor, spears, arquebuses and tiger squat cannons. In addition, Liaodong, which is becoming more and more prosperous, has also greatly improved the morale of the Liaodong garrison, so the Liaodong Army is now brave and high-spirited, and Zhu Yunwen has high hopes for it.

Geng Xuan has now inherited the title of Marquis of Changxing from his father Geng Bingwen, whose father died at the hands of Zhu Di, so Geng Xuan has always been determined to break through Beiping and kill Zhu Di, according to the emperor's promise, he can be promoted to another level and become a duke. He very much hoped that the emperor would make him the Duke of Lieguo and completely inherit his father's title.

The first step of attacking Beiping is to conquer Yongping, but Yongping City is too difficult to capture, its city is not strong but three zhang, the circumference is not more than ten miles, but its topography is very special, the east, the northeast, the north are respectively when the mountain, Yongfeng Mountain and Pingshan, the west is the Qi River, only a hundred steps away from the city, in order to prevent the Qi River from scouring the riverbank, since the Yuan Dynasty has built the river embankment with bluestone, after the Qi River crosses the west embankment, it flows into the Luan River, the Luan River flows from the south of Yongping City, and then flows into the Bohai Sea through Luanzhou and Leting.

Yongping City is crescent-shaped, the north gate is northeast, the terrain is narrow, and it is impossible to attack the city on a large scale; The west gate was on the verge of the Qi River and could not be attacked; The south gate is not far from the Luanhe River, there is a wetland outside the gate, and there is even a lotus pond, the soldiers can not be mobilized quickly, the siege is inconvenient, even if the strategy of Sheng Yong is used, it is also difficult, the heavy Wuhan Iron and Steel car, the tiger squat cannon can not move quickly, it is easy to become the target of the city; As for the east side, it is a blocking mountain, Yongping City is built against the mountain, it is difficult to move on the slope, and it is impossible to launch a large number of troops to attack the city, and once the siege fails, the soldiers cannot evacuate quickly, and they will inevitably become the target of the soldiers on the hillside. Therefore, Geng Xuan attacked Yongping for the first time, and had no choice but to evacuate quickly.

From Geng Xuan's report, Zhu Yunwen understood the difficulties in conquering Yongping, and immediately summoned the craftsmen of the General Staff Department and the Engineering College to make firearms, and asked them to find a solution. After the plan was reported to Zhu Yunwen, Zhu Yunwen was noncommittal, but encouraged them to conduct a detailed simulation test. After more than ten days of testing, Zhu Yunwen, Wang Du, and Liu Jing all thought it was feasible. Therefore, at the beginning of March, Zhu Yunwen ordered Huo Zhongyun to lead a team and lead more than a dozen staff officers and firearms craftsmen to board the ship from Dengzhou, Shandong Province, and rushed to Liaodong to support Geng Xuan.

After Huo Zhongyun arrived in Liaodong, he immediately reported the siege plan to Geng Xuan, the capital of Liaodong. After watching their demonstrations, Geng Xuan's confidence increased greatly, so he immediately ordered to gather a large army and set out for Yongping. Due to the entry of most of the Mongolian army, the pressure on the Liaodong Army was greatly reduced, and more troops could be transferred, but in order to gain time, Geng Xuan only brought 50,000 people first, and the follow-up army continued to assemble to Guangning, and Keri entered the pass.

Li Rang reinforced Yongping to take the Zunhua line, Zhu Di built a pontoon bridge there, but Wu Sheng and Qiu Zengshi did not dare to easily enter the Zunhua line, because it was very close to the Xifeng Pass, so the two of them could only deploy in Qian'an in the north of Yongping, in addition to guarding against Li Rang, but also against the Mongolian army at the Xifeng Pass to go south.

On April 19, the follow-up reinforcements of 30,000 cavalry arrived in Yongping one after another, so that Geng Xuan's cavalry reached 50,000, but he did not give Wu Sheng reinforcements, but let the cavalry hide in the north of Yongping, preparing to ambush the enemy who reinforced Yongping from the north.

There were 15,000 people in Yongping City, the total soldier was Liu Jiang, and Guo Liang was his deputy. When Geng Xuan's troops approached the city of Yongping, the two immediately asked Beiping for help, but they also knew the situation in Beiping, and it was impossible for Zhu Di to send them too many men. But until Geng Xuan officially attacked the city, there was still no trace of reinforcements, which couldn't help but make the two of them a little worried, it was really Sheng Yong's attack on Tongzhou day and night, which gave them too much shock. However, after so many days, Sheng Yong's siege tactics are no secret, Liu Jiang and Guo Liang have made some preparations, but the apprehension in their hearts cannot be avoided.

Liu Jiang and Guo Liang were extremely clever people, they first collected a large number of sacks, loaded them with soil, and piled them on the head of the city, and then arranged hidden caves near the city wall to facilitate the soldiers to hide, and finally they also arranged observation posts on the city tower, using drums and gongs as signals to remind the soldiers to hide.

From the four-zhang high city tower, the city is completely unobstructed by observing the city with a telescope, so the observation post can clearly see the loading and ignition of the tiger squat cannon. As soon as the tiger cannon was spotted on fire, the observation post immediately sounded the gong, and the soldiers would hide behind the hiding hole and sack.

If the Liaodong army approached, when under the city, the soldiers used rolling wood and stones, and when the Liaodong army was about to climb the city wall, the soldiers would use the spears in their hands to stab the Liaodong army down. Liu Jiang strictly ordered that no machetes should be used, but a group of three to five people would stab the Liaodong army in the city according to the order.

In this way, the Yongping Army and the Liaodong Army launched attrition, and the slow-moving Liaodong Army was far from being able to achieve the combat effect of the Shengyong Army, and suffered heavy casualties. Sheng Yong conquered Tongzhou, with more than 10,000 casualties, and the defenders of Tongzhou also suffered more than 10,000 casualties, with a comparable killing strategy, and there were tiger squatting cannons at the head of Tongzhou City. At this time, the Liaodong Army had more casualties than the Yongping Army.

Therefore, after half a day of siege, Geng Xuan had to order to stop the attack and study countermeasures. When the Liaodong army retreated, there was a thunderous cheer on the head of Yongping City, the Yongping army had an instinctive fear of the tiger squat artillery, and also had a pessimistic attitude towards today's battle situation, but they did not expect that under Liu Jiang's arrangement, the Liaodong army was repelled without much casualties, which could not help but make them ecstatic.

But their cheers didn't last long, Geng Xuan immediately ordered the tiger to squat and open fire, and the cheers at the head of Yongping City stopped abruptly, but curses sounded, laughing at the Liaodong army for having no eggs, they were all cowards.

Geng Xuan threw the tiger cannon on the battlefield and did not arrange for people to guard it, intending to attract people from the city to go out of the city to steal, but Liu Jiang was unmoved and closed the city gate and did not come out.