On the one hand, the situation was urgent, and on the other hand, Xing Zhengnan, who had always wanted to show his talent and prove that he did not rely on the so-called "father's shadow" and "incompetent Yanei", was ambitious, so as soon as he got Zou Zhenyuan's general order, he immediately led his troops and horses westward and killed Yalushui (Yalu River) as fast as possible to prevent the situation from changing greatly.

Of course, the speed is the speed of travel, perennial influence of his stepfather and other members of the crossing team to plan and then act, coupled with many years of experience in fighting with your uncles, Xing Zhengnan is still very cautious in the march formation. Although the army moved quickly, it never rushed to the road. Rest when it's time to rest, increase reconnaissance when it's time to step up reconnaissance, and never take the enemy lightly where it should be cautiously passed. Therefore, when on the afternoon of June 21 of the lunar calendar of the seventh year of Jianlong, he led his troops to march all the way to Kaizhou, which was forty miles away from the former important town of Bohai State and now the abandoned city of Kaizhou, he did not rush to complete this distance so that the army could rest in the city - although the city of Kaizhou had been abandoned for many years, no matter how dilapidated the city was, it could shelter from the wind and rain better than the trees in the wild. Instead, he ordered to camp on the spot, and sent a large number of scouts to investigate the situation.

Xing Zhengnan's actions were naturally due to his cautious personality on the one hand, and on the other hand, he was also worried about the changes in the situation. After all, although the city of Kaiju had been abandoned after the destruction of the Balhae Kingdom, and all of its original inhabitants had been relocated, it had been the main garrison of the Khitan elite cavalry who were tasked with monitoring Goryeo as a strategic point close to Goryeo. Although with the victory of the Zhou army's Northern Expedition, a large number of 15,000 Khitan elite cavalry and Jurchen soldiers stationed here were transferred to Liaoyang City to assist in the defense, according to the data provided by the former Tokyo Left-behind Mansion, there should be more than 3,000 soldiers and horses of the former Liao State who stayed here. Before sending an accompanying "messenger" to recruit the defenders, Xing Zhengguo thought it necessary to find out the situation in the abandoned city first, so as to prevent a situation similar to that of Ningzhou -- although there has been no report of a large number of Bohai people approaching the abandoned city of Kaizhou, but in the chaos caused by the Northern Expedition of the Zhou army, who can guarantee that the original information transmission channel of the Liao State can still operate normally and transmit news from various places to Liaoyang City in a timely manner. Therefore, Xing Zhengnan would rather delay the pace of the march a little later than lead the army to advance in order to arrive at Yalushui (Yalu River) a few hours early.

Facts proved that Xing Zhengnan's caution was still very correct, and the scout scouts who went out to investigate in the evening not only sent back the news that 15,000 Bohai soldiers and horses had surrounded the abandoned city of Kaizhou, but also brought two "prisoners" to his own commander. However, to Xing Zhengnan's surprise, the two "captives" were not Bohai people, but Khitans who had been replaced as fake. Or, according to the envoy sent by Yeluxian, who accompanied him, the two Khitans should not be called "captives" at all, but messengers who were ordered to go to Liaoyang City to ask for help from their new master, Zhou Jun. Although it was a little unbelievable, after listening to the interpreter around him and the messenger sent by Ye Luxian with roughly the same meaning, Xing Zhengnan also had to sigh that the world was unpredictable, and at the same time believed that there was really something that happened when the former Liao State Kaizhou guard sent someone to rescue the Zhou army.

According to the two so-called "messengers", as early as ten days ago, that is, on the eleventh day of the sixth lunar month of the seventh year of Jianlong, their main general, Yelu Zhijie, had learned from a group of Jurchen herdsmen who had fled Liaoyang City to return to their tribe and passed through the abandoned city of Kaizhou that Liaoyang City had been captured by the Zhou army, the old emperor had been assassinated by his slaves, and the new emperor and a number of important officials in the court had been captured by the Zhou army and surrendered. At that time, Yelu Zhijie's first reaction was to abandon the city and flee, and take his cronies to the territory of the Jurchen Yalushui Department, which was not far away and had a good relationship with him before, to take refuge for a while. But as soon as he came, considering that his family members were all in Liaoyang City, others could ignore it, but his mother and three underage sons could not be abandoned. Second, he did not dare to guarantee that in the face of the menacing Zhou army, the Jurchens of the Yalushui Department would be desperate to protect themselves, and would not hand themselves over for the safety and interests of their own tribe in exchange for the preferential treatment and trust of the Zhou army. Therefore, after careful consideration and consideration, especially after learning that the new emperor Yeluxian had sent an envoy with a holy decree to recruit the officials and generals of various prefectures and counties, Yelu Zhijie still decided to stay in the military camp in the ruined city of Kaizhou, wait for the arrival of the envoy of the new Son of Heaven, and then surrender by order.

Unexpectedly, the messenger of the Son of Heaven did not wait, but the 15,000 Bohai army led by Wang Ji (Da Guangxian) had already arrived in the city three days ago. In the face of Wang Ji (Da Guangxian) threw out that as long as he returns to the Bohai Sea now, the success of the restoration of the country in the future is indispensable to his own position as a prince, and if he resists stubbornly, there is only a dead end, Yelu Zhijie has also hesitated and wavered. However, the arrogance, arrogance and lack of attention shown by Wang Ji (Da Guangxian), who felt that he had the chance to win, made the former Khitan nobleman feel humiliated, and at the same time, he was also very optimistic about the results of the so-called "Bohai Restoration", and made up his mind to fight the other party to the end and swear not to surrender. It is a pity that determination and courage are not enough to fight a war. In the face of 15,000 wolf-like Bohai generals, although the remaining 3,000 old and weak remnants in Yelu Zhijie's hands supported them with their bloody courage and did not let the other party break the city for three days, they were already at the end of the crossbow, and it was only a matter of time before the entire army was wiped out. It was in this critical situation that Yelu Zhijie held the idea of "a dead horse as a live horse doctor", and sent a group of dead soldiers to break out of the encirclement of the Bohai Navy and go to Liaoyang City to ask the Zhou army for reinforcements.

As the saying goes, "saving soldiers is like fighting fire", on the one hand, Kaizhou City is already in danger, and the 3,000 Khitan defenders in the city are in danger of being wiped out if they are one step late; On the other hand, as the Khitan dead soldiers broke through the siege, the Bohai people besieging the city would definitely guess that the purpose of their breakthrough was to seek reinforcements and strengthen their guards, in case the other side really moved to the rescue. In other words, the longer they delay here, the tighter the Bohai people's defenses will be, and the fiercer the battle will be. Although he is full of confidence in the combat effectiveness of his own soldiers, if he has the opportunity to achieve the greatest results at the lowest cost, why not do it. So, after ordering someone to bring the scarred Khitan messenger down to the good life for treatment and hospitality, Xing Zhengnan thought about it for a while, and ordered the troops to be divided into three routes, with the "Security Army" infantry regiment as the garrison detachment, staying in his own camp to protect the baggage; The main force of the cavalry regiment of the Fifth Composite Infantry Division of the "Flying Dragon Army" formed an interception detachment, marched covertly, bypassed the abandoned city of Kaizhou, and ambushed the necessary road from Kaizhou to the bank of the Yalu River (Yalu River) to block the Bohai Navy that fled from Kaizhou City; The main attack detachment was formed with other soldiers and horses of the provisional brigade to attack the Bohai Navy under the ruined city of Kaizhou from the front.

In order to achieve the best effect, Xing Zhengnan set the time of the attack in the middle of the night. On the one hand, with the help of the cover of night, the Zhou army could get as close as possible to the camp of the Bohai Navy without being detected. On the other hand, if a person is suddenly attacked while sleeping soundly, his reaction speed and agility will be greatly reduced. Therefore, after the early dinner, the entire provisional brigade was asked to seize the time to rest and sleep, except for a few necessary patrol posts, so that they could have sufficient physical strength and energy to carry out operations at night.

The Zhou army seized the time to recuperate, but the Bohai Navy under the abandoned city of Kaizhou stepped up its attack under the supervision of Wang Ji (Da Guangxian), and there was a momentum of vowing not to give up if the city was not taken. Although his advisers had more than once suggested that Wang Ji (Da Guangxian) send a detachment of soldiers out of the city for 30 miles after several Khitan dead soldiers had successfully broken through the siege, in case those dead soldiers moved to the rescue. But as soon as he came, Wang Ji (Da Guangxian) thought that as long as his side strengthened the offensive and broke through the abandoned city in front of him, which was only guarded by less than 3,000 Khitan old and weak remnants, it was in front of him, even if those Khitan dead soldiers put on their wings and flew to Liaoyang City, the rescuers would not have time to rush to Kaizhou. Second, according to the news obtained before, the Zhou army had conquered Liaoyang at the beginning of the month, and the monarchs and ministers of the Liao State were captured, and the Liao State no longer existed, and where were the rescuers to rescue Kaizhou. As for the Zhou army, not to mention that it had no possibility of rescuing the three thousand old and weak Khitan soldiers in an abandoned city. Even if they wanted to save it, they did not have enough troops to help them when the Bohai people in Ningzhou, Fuzhou and other places resisted desperately, and the Bohai people in the entire Tokyo Province were restless. Therefore, Wang Ji (Da Guangxian) did not take it seriously with the suggestions and worries of his advisers, and had no other means of prevention except for the fact that he had to send a few additional scout scouts to strengthen the investigation in the direction of Liaoyang City, so as to show the advantages of his humble admonition.