Before the Eastern Han Dynasty, the Kushan Mountains were almost isolated between the Central Plains and the eastern part of Guanzhong, and all land transportation only existed in the northern part of the Kushan Mountains near the Yellow River, where there was a crack more than 20 miles long.

And the entrance to this crack is the location of Hangu Pass.

At that time, if you wanted to capture Hangu Pass, you had to cross the turbulent Hongnong River in front of the defenders before you could attack the wall of Hangu Pass, which was nearly five zhang high.

Even if you are lucky enough to capture the pass, you still need to pass through a narrow valley that is more than 20 miles long and can only accommodate several people in parallel, and the march is very risky.

This is the reason why the Qin State can sit firmly in Guanzhong.

However, even if Hangu Pass can withstand a million troops, it cannot stop the great power of nature.

By the end of the Eastern Han Dynasty, due to the continuous erosion of the Yellow River, the Yellow River north of Hangu Pass began to shift northward, coupled with the large amount of sediment brought by the Yellow River, which continued to accumulate in the north of the river bank, and finally formed a large shoal.

It was precisely because of the appearance of this shoal that the army attacking from the east could no longer pass through the Hangu Pass, but could directly attack the Guanzhong Plain from the north bank of the river, bypassing the Kunshan Mountain Range.

Therefore, Tongguan came into being.

Since the end of the Eastern Han Dynasty, there has been the place name Tongguan.

It's just that Tongguan at the end of the Han Dynasty still walked 140 miles to the west, on a platform called Lintoe Plateau.

The north side of the Lintoe Plateau is close to the Yellow River, and the river water flows directly close to the plateau.

The south side of the Linzhi Plateau is connected to the Qinling Mountains, and the mountains are so steep that the army cannot bypass them.

At the end of the Han Dynasty, Tongguan was set up at the commanding height of the mountain road, and the army coming from the east had to first pass through a narrow mountain road called "Huangxiangban".

And this "Yellow Lane Ridge" is only a few meters wide, which can only accommodate a few people to advance side by side, and is an excellent place to set up an ambush.

After the army passed through the mountain road of "Huangxiangban", it also needed to climb to the top of Lintoe Plateau to see the steep Tongguan city wall.

Even if the Hantong Pass was conquered, the army still had to enter a steep river valley called the "forbidden ditch", continue to pass north, and only after arriving at the confluence of Weishui and Tongshui did it enter the Guanzhong area.

Hantong Pass is as dangerous, but the years are still a pig-killing knife, no matter whether you are a famous general and a beauty, or the Xiongcheng Pass cannot resist it.

After hundreds of years have passed, the same plot of geological changes happened to Hantong Pass again.

At the end of the Sui Dynasty and the beginning of the Tang Dynasty, because the course of the Yellow River continued to change to the north and the water level also dropped, a large shoal appeared on the north side of the Linzhi Plateau, which was once close to the Yellow River.

The army coming from the east did not need to cross the mountains and mountains to storm the Hantong Pass, but could walk along the shallows by the river into the pass.

Therefore, in the year of Tianzhu, that is, the second year of Wu Zetian's accession to the throne, in 691 AD, Tongguan was moved north from Lintoe Plateau to the bank of the Yellow River to guard the new passage.

The current Tongguan, bordering the Yellow River in the north, looks more precipitous than the previous Hantong Pass.

"This place is really precipitous, if there is no 100,000 troops, it is impossible to break through Tongguan head-on."

Wang Yu stood on the mountain beam and looked at Tongguan.

The wind and snow continued to hit his stained face.

"Yes, General Wang is really resourceful! The last general didn't expect that there was still a way to bypass Tongguan! ”

Pei Kuan boasted on the side.

The look on his face was also extremely admirable.

Wang Yu said with a smile: "It has only been forty-six years since the completion of Xintong Pass, and Ben Jiang is already fifty-six years old. ”

"When Ben was young, he had to walk this road every year, so he was naturally very familiar with it."

"From the day of the establishment of Xintong Pass, Emperor Wu has forbidden business travelers to pass on this Hantong Pass road, completely abandoned this road, and set up twelve small passes on the road to prevent people from smuggling."

"That kid Li Mao didn't understand the changes in the history of Tongguan at all, so he naturally didn't know that this path could bypass Xintongguan, so he didn't send troops to receive it."

Pei Kuan is from the Pei family in Hedong, and when Wang Yu served as the envoy of the Hedong Festival, the Pei family has always been fully supportive, so Wang Yu is naturally very willing to promote the future.

"Then don't we have to fight Tongguan? You can directly make a detour into the pass and capture Li Mao alive! Pei Kuan looked at Tongguan City in the distance and said excitedly.

If Li Mao can be caught with his own hands, it means that the shame of the previous defeat will be completely washed away.

And he also saw the figures walking around Tongguan City, and knew that a strong attack might not be able to take it.

Wang Yu glanced at the moon in the sky, shook his head and said, "No! We don't need to be at risk! ”

"After five days of continuous rapid marching, most of the soldiers could not hold on."

"It will take at least a day for the army to cross the Kunshan Mountains from here, and the news that we will detour through the old road to Tongguan will definitely spread, and when the time comes, we will be blocked in the Kunshan Mountains, and the whole army will be annihilated."

"What's more, Your Majesty has already summoned the King of Soldiers and Horses in the world, and decided to drive the expedition in person, the two of us have finished the matter, what should Your Majesty do?"

Pei Kuan suddenly understood.

As long as he can win Tongguan, the task has been completed for Wang Yu, and it is enough to get the first merit of exterminating the anti-thieves.

Wang Yu is also afraid of being overshadowed by high merit, afraid of being hidden by the birds with good bows, and the cunning rabbit is cooked by the dead lackeys.

But this is not what he wants!

What Pei Kuan wants most in his heart is to capture Li Mao alive in Chang'an City, not just to take down a Chang'an City.

"Doesn't the general want to be crowned king? If you can break into Chang'an, you will have the merit of Kuang Fu Sheji, and Your Majesty will definitely give it to the king. Pei Kuan said bewildermently.

"Huh!"

Wang Yu chuckled, "Ben will be sixty out of fifty this year, and he is already half buried in the loess!" What if you are crowned a king? ”

"You were born in the Pei clan in Hedong, and you will be born in the Taiyuan Wang clan. Our family has lasted for thousands of years, and what kind of identity has not appeared? ”

"Ben Jiang and your brother Pei Yaoqing are close friends, so I'll tell you the truth, the king with a different surname in the imperial court has not been taken into account yet."

Pei Kuan carefully understood Wang Yu's words, and suddenly became enlightened.

Longxi Li, Zhaojun Li, Boling Cui, Qinghe Cui, Fanyang Lu, Xingyang Zheng, and Taiyuan Wang are known as the five surnames and seven wangs in the Tang Dynasty.

These families can't even look down on marrying with the royal family, so how can they risk their lives for the identity of a king with a different surname?

"The Admiral understands!"

Pei Kuan no longer persuaded him.

Wang Yu saw that he was so teachable, and said with relief: "There are still three hours before dawn, go back and rest first." ”

"After dawn, the soldiers have replenished their physical strength, and you will go to be a pioneer officer!"

The vanguard officer is not a warrior who climbs first, and does not need to climb the wall himself, but only commands from behind.

Wang Yu originally wanted to arrange this position for his own family, but thinking that Pei Kuan had won the trust of the emperor at this time, he gave up this great achievement.

Pei Kuanjiu has been in the army for a long time, and he also understands this unspoken rule, and hurriedly thanked, "Thank you for the general's love!" ”