Since Shangdang and Yiguan fell into the hands of the Tang Dynasty, Yan Guo has been particularly concerned about the defense of Hanoi. Especially after Henan County was taken by the Tang Dynasty recently, Hanoi County has become a very important place for Yan Kingdom.

Whether it is from Shangdang to Taihang, or to go out of the pass, or directly from Luoyang to the north to attack the hinterland of Yan. In short, Hanoi is a must-visit place.

So, in a strategic sense, Hanoi is no less than a key place. As long as Yan Guo can firmly grasp this place, it will be able to block the Tang army in these three places to the south of Yecheng, so that it will not be able to form a threat.

But now, Li Xin has found a breakthrough, which is a golden opportunity.

If you really rely on your own initiative to go out of the mountain, and then fight down city by city, and take down the entire Hanoi County, the difficulty and cost will definitely be very great.

After receiving Lu Hu's reply, Li Xin began to prepare for the war. At this time, in addition to him and Liu Xiaohai, there were also Zhao Ji and Chen Kang in the south. Of course, the two of them were just given orders and knew what they were supposed to do, but they didn't show it.

At the end of May, Li Xin and Liu Xiaohai agreed on the same night to leave Taihang Mountain and go straight to their respective goals.

Li Xin led his army straight to Yi County, as long as he controlled this county seat, then Heyang County in the south and Qinshui County in the north would be constrained.

After Lu Guang's soldiers and horses left the bowl city pass, they went straight to Yewang County. Then, his soldiers and horses stopped outside Yewang County, surrounded the entire county, and began to attack continuously. Of course, this attack is a bit odd, because it's just a big one.

In order to defend against the Tang army, Yan Guo garrisoned 10,000 troops in Yixian, mainly in the direction of defending Yiguan.

In Heyang County, to the south, 10,000 troops were also deployed, and the defensive direction was Heyin County opposite, and the Tang army guarding the Yellow River to defend the opposite bank crossed the river.

Li Xin's sudden dispatch of troops really caught the 10,000 Yan troops in Yixian County a little unprepared. After all, this side has been relatively stable these days, especially in the southern part of Shangdang and Yiguan, and there has not been a major war for several years.

The generals in the city didn't know that Li Xin was in the army, they just saw that there were only more than 5,000 Tang troops outside the city, and they actually dared to attack Yixian, which had an army of tens of thousands, and they couldn't help but feel despised by them.

General Yan, who led the troops, felt that this was a rare opportunity, so he raised the army in the city and prepared to wipe out the five thousand Tang troops outside the city. In this way, I don't have to stay in this place where no fault is merit all the time, no matter what, it can be regarded as a great achievement!

A hasty decision will inevitably have serious consequences. This careless guy left the city and fought a tough battle with the Tang army outside the city, however, in front of the unbroken army, his 10,000 horses had no chance of winning at all.

In less than an hour, 10,000 troops were killed and wounded, and even the defenders were killed in battle. Some of the soldiers who managed to escape with great difficulty fled to the east, or directly to Heyang County in the south.

As a result, Yixian County immediately fell into the hands of Datang. Then, Li Xin ordered the soldiers and horses who arrived later to take over the city, while he led Deng Qiang and the 3,000 unbroken army to the south to kill Benheyang County.

As for Qinshui County to the north, the garrison in that place was relatively small, only 3,000 people. Therefore, Li Xin ordered Zhang Hao to lead 2,000 soldiers and horses to take it.

After receiving the news of the defeat in Yi County, Heyang County was immediately frightened.

After all, after losing the echo of Yi County, Heyang County is in a situation of being attacked from the north and south.

Although there are also 10,000 troops in their hands, since the Tang army can defeat the Yixian army, it should not be a problem to defeat themselves.

Because he learned the lesson of the Yan army in Yixian County, he knew that the Tang army that came this time was very powerful. Therefore, the defenders of Heyang County simply closed the city and defended themselves, and did not intend to fight hard with the Tang army. At the same time, they quickly sent people to inform the counties in the county, and sent messengers to Yedu to report for help.

In Yecheng, Murong Ke received a lot of urgent reports from Hanoi County for a while, especially the official documents issued by Lu Hufa, but there were still them in the first few days, and then they were cut off.

And judging from the news in his hand, Murong Ke also knew that Yewang County was besieged, so Lu Hu could no longer ask for help.

At this time, he finally understood that the Tang Army's target was not Youji and other places at all, but Hanoi County. After understanding this, it was naturally impossible for him to be indifferent and let the Tang army occupy Hanoi County.

On the one hand, he ordered the remaining army of Hanoi County, in addition to holding on to the counties, and immediately mobilized 20,000 troops from around Yecheng to the south, and stationed them between Huai County and Shanyang County, the easternmost part of Hanoi County.

On the other hand, another 20,000 troops were sent south. The 20,000 troops really went to the rescue of the counties of Hanoi County, and their purpose was to fight the Tang army in Hanoi County.

Huai County is located in the north of the Yellow River, and Shanyang County is located at the foot of Taihang Mountain, and the distance between the north and south of the two places is about 40 miles. Because there are Taihang Mountains in the north and the surging Yellow River in the south, once a heavy army is deployed on this narrow strip of land, I am afraid that if you want to go over, you will have to fight hard.

If it can't be fought, the Tang army will have to stop hundreds of miles away from Yecheng and will not be able to move forward. For Yan Guo, this means success, although a few county towns are lost, as long as the capital is kept, everything is worth it.

What's more, before this line of defense can be reached, the Tang army has to defeat the 30,000 or 40,000 Yan troops in Hanoi County. One attack and one defense, Murong Ke's deployment is very rigorous.

Regarding Murong Ke's reaction, Li Xin had actually expected it a long time ago. After all, as long as you put yourself in the other person's position, after a little consideration, you will inevitably come up with such a solution.

In addition to this part of the soldiers and horses, the counties of Xingyang County on the other side of Hanoi County have also strengthened their vigilance, especially several counties near the line of the Yellow River, especially guarding against the Tang army coming from Hanoi County.

Because if you do that, you can bypass the Tiger Prison Pass in front and land directly on the east coast of the Tiger Prison Pass into the territory of Xingyang County.

The enemy army in Heyang County retreated in the city to wait for reinforcements, and Li Xin did not directly attack the city, but after showing off his might under the city for a while, he led the army to leave directly.

At the same time, there was good news from Qinshui County, and Zhang Hao led the army to attack and take the city down in one fell swoop.

As a result, the western part of Hanoi County, except for Ha Duong County, was taken. The time had come, and Hedong and other places had already prepared soldiers and horses, and they immediately passed through the pass and stationed in Hanoi County.

Li Xin left without a fight, which was not a good thing for the Yan army in Heyang County. Although their side was out of trouble because of this, they all knew that if Li Xin didn't have enough benefits, it would be impossible for him to give up Heyang County.

At this time, there is a difficult problem in front of them, whether to chase them out or not?

Comparatively speaking, the other counties of Hanoi County basically have only a small number of garrisons. After all, not everywhere faces the threat of the Don Army.

In some counties far away from the Tang army, such as Shanyang County and Huai County, the number of garrisons has just reached about 1,000 people, which is an urgent increase after the loss of Henan County.

Among the nine counties of Hanoi County, four counties are on the north bank of the Yellow River, and three counties are not far from the foot of the Taihang Mountains. The remaining two counties are located in the middle zone, one is in the west, near the Wangwu Mountain Yiguan. The other one is a state and county located dozens of miles southeast of Yewang County.

Among the nine counties, the four counties of Yixian, Heyang, Yewang and Wenxian are stationed with heavy troops because they are either facing Yiguan, or facing Wanzichengguan and the Yellow River. Yewang County is even more because it is where Lu Hu's lair is located, so there are more troops.

In other counties, the number of troops is basically the same as that of Qinshui County, or even much less. The further east, the farther away from the Tang army, the fewer troops.

As a result, one consequence is that when Li Xin moves his army eastward, it is very likely that no one will be able to stop him. Although I don't know when the reinforcements from the imperial court will arrive, they definitely can't be too soon.

Before that, if Li Xin and the others could not be dragged down and buy time for the imperial court reinforcements to go south, it would obviously be detrimental to the overall situation.

Moreover, once all the eastern counties were lost, Heyang County became an isolated city. In the case of a long delay without help, the destruction of the city is also inevitable.

Therefore, after discussing for a long time, the Yan army guarding the city finally decided to pursue the Tang army and drag this Tang army to stop.

They were also cautious, and out of an army of more than 10,000, only 7,000 men and horses were sent in pursuit. If there are still three or four thousand guards left in the city, even if the pursuit fails, at least the city will not be lost.

The problem is that their ideas are a little too naïve.

Li Xin was waiting for them to leave the city, so naturally he wouldn't let them go back. At the same time, after taking Qinshui County, Zhang Oyster quietly went south from the north, far behind the 7,000 Yan army.

So, when the Yan army caught up with the Tang army more than 20 miles away from Heyang County, it was immediately surrounded in turn. Although there were more than 7,000 people, they were quickly annihilated under the front and rear attacks of the 5,000 unbroken army.

After dealing with this group of enemy troops, Li Xin immediately waved his army and killed it, and attacked the east and west gates of Heyang County with 5,000 troops. The Yan army, who was already unsettled, was even more terrified when he heard that the 7,000 soldiers and horses had been annihilated.

Therefore, Heyang County did not last long, and it was directly broken.