In 416, Later Qin Yao Xing died of illness and was succeeded by the crown prince Yao Hong.
Yao Hong, who had just succeeded to the throne, was slightly immature and difficult to stabilize the overall situation, and Later Qin fell into chaos, allowing Liu Yu to see an opportunity to take advantage of.
Later Qin was close to the Eastern Jin Dynasty, and Later Qin's territory was not small, chang'an and Luoyang and other important cities were in the hands of Later Qin, Yao Xing had just died, if he could seize the opportunity of Later Qin's chaos to occupy Later Qin, it would be very beneficial to his own development. After much deliberation, Liu Yu decided to seize the opportunity of Yao Xing's death and personally lead his troops to attack Later Qin.
After deciding to personally lead the army against Later Qin, Liu Yu had to solve a problem: Who would Jiankang hand over to guard the town?
Thinking about it, Liu Yu decided to entrust the heavy responsibility of Zhen Shou Jiankang to his confidant, Liu Muzhi.
In 416, after arranging the rear, Liu Yu began the Northern Expedition to Later Qin, and there was also a "General Long Jun" in his forward, and Liu Yu's "General Long Jun" was not an ordinary person, he was Liu Yu's fierce general- Wang Zhen evil.
Wang Zhen evil was the grandson of Former Qin's heavy minister Wang Meng, Who was resourceful and judgmental, and was deeply respected by the Former Qin monarch, and as a descendant of a heavy minister, Wang Zhen evil's future would have been bright. However, there were unexpected storms in the sky, and in the year when Wang Zhen evil was thirteen years old, the Battle of Shuishui broke out, Jian Jian was defeated, the Former Qin Empire collapsed, and the young Wang Zhen Evil thus lived a life of upheaval and displacement.
Later, Wang Zhen evil followed his uncle to the Eastern Jin Dynasty and lived in the Jingzhou area, and the young Wang Zhen evil, like his grandfather Wang Meng, also liked to read books on the art of war and was very interested in studying the situation in the world.
Because of his military knowledge, some people recommended Wang Zhen evil to Liu Yu, and after Liu Yu and Wang Zhen evil met and talked, they greatly appreciated his talent, learned that Wang Zhen evil was Wang Meng's descendant, and even praised him as a "general with a general", and immediately promoted Wang Zhen evil.
After joining Liu Yu's team, due to Wang Zhen's outstanding performance, this crusade against Later Qin, Liu Yu decided to let Wang Zhen evil continue to serve as a forward and attack the eastern region of Later Qin, and Liu Yu then led his troops to follow.
The general Tan Daoji had followed Liu Yu in battle at an early age, and had made great achievements in the battle against Lu Xun, and this time he was made a champion general and went out with Wang Zhenxi to attack Later Qin.
In addition, in order to confuse the enemy, Liu Yu also arranged a "suspicious army": let the general Shen Tianzi take a small number of men and horses to attack the southern region of Later Qin.
In 416, Wang Zhenxi and Tan Daoji led a large army north from the Huai River area of influence of the Eastern Jin Dynasty to attack the areas of Xuchang and Luoyang under Later Qin control.
At that time, the Later Qin monarch Yao Xing had just died, and Yao Hong, who succeeded to the throne, was unable to control the overall situation, and the people of Later Qin were unstable, while Wang Zhen's troops were prepared and morale was like a rainbow, and they quickly laid down Xuchang and pushed into Luoyang. Yao Xie, who was guarding Luoyang, saw that the Eastern Jin forces were threatening and directly surrendered, and Wang Zhenyi easily took Luoyang. Then marched west, approaching Tongguan.
Luoyang is far from the core area of Later Qin, Guanzhong, the so-called "Guanzhong", refers to the central part of today's Shaanxi Province, this area has Tongguan in the east, Wuguan in the south, Sanguan in the west, Xiaoguan in the north, located in the four passes, so it is called "Guanzhong", which has always been a place where soldiers and families must fight.
Later Qin's defensive strength around Luoyang was relatively weak and relatively easy to fight, while Tongguan was different, Tongguan was the gateway to Guanzhong, where Wang Zhenxian encountered a hard nail.
Tongguan was located between the Yellow River and the high mountains, easy to defend and difficult to attack, and the veteran Qin general Yao Shao made full use of the advantages of the terrain and led the troops to strictly guard against death, and It was difficult for Wang Zhen's troops to advance, and at the same time, because the breakthrough was too fast, the logistics and transportation could not keep up, resulting in the troops beginning to lack food.
Wang Zhen evil had to send someone to ask Liu Yu for help from following behind, but he did not expect that Liu Yu was also in trouble.
Liu Yu led his army to board a warship and marched along the Yellow River into the hinterland of Later Qin, but did not encounter any resistance from Later Qin, but encountered another strong enemy, the Northern Wei army.
Northern Wei had also been paying attention to such a major event as Liu Yu's attack on Qin, when the north of the Yellow River was occupied by Northern Wei, and Northern Wei sent 100,000 troops to guard against Eastern Jin forces on the north bank of the Yellow River.
At that time, the Yellow River was flowing rapidly, if the ships of the Eastern Jin Dynasty accidentally drifted to the north bank, they would be intercepted and killed by the Northern Wei cavalry, if the Eastern Jin troops crossed the river to retaliate, the Northern Wei cavalry immediately withdrew on horseback, and after the Eastern Jin people immediately took the boat, they would come to the shore to harass, which seriously affected the marching speed of the Eastern Jin troops.
The reason why the Northern Wei dared to be so arrogant was because they had powerful cavalry. Liu Yu pondered for a long time and came up with a formation of "riding with steps", that is, the famous "But Moon Array".
Liu Yu sent a fierce general Ding Wu with hundreds of soldiers, plus more than a hundred chariots, to board the north bank of the Yellow River and pose on the shore with the "Moon Array", which was in the shape of a half moon, with both ends at the water's edge and protruding in the middle.
The Northern Wei cavalry saw that the other side suddenly posed a formation, did not know what medicine they were selling in the gourd, and did not act rashly.
Taking advantage of the time when the Northern Wei people were stunned, Liu Yu ordered the general Zhu Chaoshi to quickly lead people to rush ashore, take hundreds of crossbows, and set up obstacles in front of the position, and soon built a simple defensive position, and the Northern Wei cavalry saw that the other side had set up obstacles and immediately launched an attack.
Zhu Chaoshi was a general with wisdom and courage, he ordered the whole army to shoot first with a soft bow and small arrows, the arrows did not go far before they fell to the ground, the Northern Wei cavalry looked at it, thinking that the Eastern Jin forces were not a threat, so they sent 30,000 cavalry, surrounded the "But Moon Array", and launched a strong attack.
As the Northern Wei cavalry approached, the "Moon Array" finally began to threaten.
Seeing that the enemy had entered the firing range, Zhu Chaoshi ordered a hundred crossbows to be fired in unison, and the Northern Wei cavalry were hit by arrows, but they continued to charge forward with their own many people, at this time Zhu Chaoshi took out a large killing weapon. When he came ashore, Zhu Chaoshi led the crowd to bring a lot of sledgehammers and more than a thousand long hammers, he ordered the soldiers to make the long hammer three or four feet long, put it on top of the crossbow, shoot with a hammer, under the powerful force of the crossbow, a "giant arrow" shot at the enemy, the Northern Wei cavalry is very close, the people are dense, and a hammer can often penetrate three or four Northern Wei cavalry.
After being hit by such a terrible killing weapon, the Northern Wei cavalry suffered heavy losses and fled one after another, allowing Liu Yu to march forward smoothly.
Although Wang Zhenyi could not get Liu Yu's support for the time being, he did not panic in the face of the problem of food shortage, and immediately sent people to collect grain on the spot, temporarily solving the problem of food shortage.
Soon after, Liu Yu led his army to arrive, and the Tongguan general Yao Shao suddenly fell ill and died, and in his place, yao Zan, saw that the Eastern Jin army was crowded and led the army to retreat.
Later Qin monarch Yao Hong, on the one hand, had to deal with Wang Zhen's evil troops from the east, and on the other hand, he had to deal with Shen Tianzi's troops from the south.
Yao Hong was originally preparing to attack Wang Zhenzi's forces, but he was worried that Shen Tianzi would sneak attack from the flank, and after thinking about it, Yao Hong decided to send troops to destroy Shen Tianzi first, and then go all out to deal with Wang Zhenzi.
Although Shen Tianzi's team was only a "suspicious soldier" sent by Liu Yu, and the number was small, Shen Tianzi fought fiercely and actually defeated the men and horses sent by Yao Hong. As a result, Yao Hong neither destroyed Shen Tianzi nor blocked Wang Zhen evil.
Shen Tianzi fought well, Wang Zhen evil performed well, he gave full play to the advantages of the Eastern Jin forces in water warfare, divided the troops into a number of light boats, along the Weishui into Guanzhong, their boat bread up, soldiers rowed inside, Qiang people saw that there was no one on the boat but could advance in the water, all of them were amazed.
After the fleet approached the vicinity of Chang'an, Wang Zhen evil let the soldiers have a full meal, and then ordered the ship to be destroyed and abandoned. After the battle began, Wang Zhen's evil troops all bravely killed the enemy, and then the Qin defenders were soon defeated due to repeated defeats and low morale, and were soon defeated.
In 417, just one year after the dispatch of troops, Wang Zhen's forces conquered the Later Qin capital Chang'an, and the Later Qin monarch Yao Hong surrendered, and Later Qin perished.