After Gao Buer pacified Jiangnan, he immediately ordered Li Jing and Hongfu Nu to lead an army of 100,000 and more than 5,000 warships from Hangzhou to Luoyang along the Beijing-Hangzhou Canal to assist Li Shimin, who was fighting with Wang Shichong.

In addition, Gao Buer also sent Zhang Zhongping to lead an army of 50,000 to attack Li Zitong, who was entrenched in Jiangdu. For Li Zitong, an old opponent, Gao Buer has never forgotten, not that he is so powerful, but under Gao Buer's strategy of first south and then north, it can survive in the crowd of heroes to this day, which makes Gao Buer incredible.

Li Zitong, who was in Jiangdu, heard that his subordinates had reported that Gao Buer, who was in Hangzhou, had arranged five or six thousand warships on the river, and 150,000 horses were preparing to cross the Yangtze River north, and he was greatly alarmed. After years of hard work, although there are some people in his hands, but there are only 60,000 people in the full battle, Xiao Milling 400,000 horses were defeated overnight, what can he do with this little man, so he ordered to give up Jiangdu.

After Li Jing and Zhang Zhongping led their troops across the Yangtze River, Zhang Zhongping built the Jiangdu and turned it into a granary for attacking Luoyang, while leading his men and horses to continue to pursue Li Zitong. In the end, Li Zitong was captured alive, and according to Gao Buer's order, he sent people to escort Chang'an, and was later killed because he was anti-Tang again.

Since last year, Li Shimin has led troops to fight Wang Shichong for more than a year, and Qin Qiong, Cheng Yanjin and other Wagang generals couldn't stand Wang Shichong's meanness and surrendered to Li Shichong, only Shan Xiongxin is still following Wang Shichong because he married Wang Shichong's daughter.

Wang Shichong currently has only one Luoyang City left in his hands, because of repeated defeats, although there are still 60,000 or 70,000 horses in his hands, which is about the same as Li Shimin's 80,000 horses, but he does not dare to go out of the city to meet the battle, but stands in the city to defend himself, and at the same time asks for help from Dou Jiande in Hebei.

Dou Jiande received Wang Shichong's letter of help, and his heart swayed left and right: "Li Tang's army is prosperous, Luoyang is determined to win, it is really unwise to fight with him at this time, but once Luoyang falls into the hands of Li Shimin, his next target must be us, what should we do?" ”

Liu Bin, a scholar from Zhongshushe, said: "King, Guanzhong is mostly the land of Emperor Longxing, and now it has been owned by Li Tang, and the land of Guanzhong has been unified in ancient times, and the reason why Li Tang has not been able to dominate the world now is because now Li Tang, we, and Wang Shichong of Luoyang have formed a three-legged trend, and the lips are dead and the teeth are cold, so Luoyang must be saved." ”

"Having said that, once we send troops to Luoyang, we are not allowed to send troops to support Luoyang from Li Yuan's sworn brotherhood in Hangzhou, and such a long-term fierce battle is even more disadvantageous to me."

"Don't worry, the king, now that Gao Fuji is fighting against Liang Guoxiao, the two sides are not scored, he must not be able to come north. Li Tang has been fighting with Wang Shichong for almost two years, and the two sides are almost fighting, as long as our army moves quickly, it will definitely defeat Li Tang's army before the end of the decisive battle in Jiangnan. ”

Liu Bin looked at Dou Jiande and said with concerns: "The king really doesn't have to worry, don't forget that Wang Shichong still has 60,000 or 70,000 soldiers and horses, and Luoyang has enough food, as long as we go to Luoyang with a light car, and Wang Shichong should cooperate with the outside world, and defeat the Tang army. ”

As soon as Dou Jiande heard that there was an opportunity to dominate the world, he was overjoyed and said: "Mr. is very strategic, okay, just listen to Mr., I will do my best to have 130,000 soldiers and horses in my country, and personally lead to support Wang Shichong." ”

Li Shimin, who was besieging Luoyang, saw that he was about to take Luoyang in the near future, but he suddenly heard that Dou Jiande led 130,000 horses to Luoyang, and was shocked.

Now Li Yuan does not have many soldiers and horses in his hands, and sent 10,000 people to help, which is enough, Li Shimin is so anxious that he burns the beams of the house, if he retreats from Luoyang, he will put the enemy into the pass, so that Chang'an is difficult to protect, and the emperor's hegemony will also be successful.

Dou Jiande is still less than a day's journey from Luoyang, and Li Shimin will discuss countermeasures.

Li Shimin said: "Now Luoyang is about to be broken by us, but Dou Jiande's men and horses are coming, if they retreat without a fight at this time, let them join forces, the enemy army will have nearly 200,000 horses, and then we will have nothing to do with them, and Chang'an is also in danger." ”

The generals had no good plan, so Li Shimin asked Qu Tutong to lead 50,000 horses to continue to besiege Luoyang, and he led 40,000 horses to Wujiao Pass to meet Dou Jiande.

The two armies faced each other for more than 20 days, and at this time, the battle between Gao Buer and Xiao Mo had ended, and the 100,000 troops led by Li Jing had less than a day's journey to Luoyang, and Li Shimin was overjoyed.

Dou Jiande's soldiers and horses were arrogant, thinking that the Jiangnan War would not end in the short term, and Li Zitong, who was entrenched in Jiangdu, Jiangnan people and horses would not cross the river to the north in the short term, so they didn't even let go of the horses, so Li Jing led the troops to him without knowing it, and he was still planning to take advantage of the lack of food and grass in Li Shimin's army to capture Wujiao Pass in one fell swoop.

Li Shimin sent someone to contact Li Jing and make an appointment for the attack, so early the next morning, Li Shimin ordered the soldiers to go out of the pass and release their horses, confuse the enemy, and attract the enemy to attack.

Dou Jiande saw that Li Shimin had put thousands of horses outside the Tiger Prison Pass to graze leisurely, and thought that the opportunity to break through the pass had arrived, so he ordered the whole army to attack.

Li Shimin stood on a high place and looked at the opponent's military horses, rushed towards the Wujiao Pass in a disorderly manner, and said to Xiao Yu, Qin Qiong, Cheng Yanjin, Shi Danai and other generals around him: "Although the other party occupies the land of Hebei and Shandong, it has never really fought against a powerful army, and the drums and trumpets in the army are different. ”

Xiao Yu surrendered to Li Yuan as early as after Li Yuan invaded Chang'an, according to Gao Buer's words, and now he is shooting for the right servant and attacking Luoyang with Li Shimin.

Dou Jiande commanded the army to come to the Wugao Pass, only to see that the gate was closed, and the military horses scattered outside the pass were no longer there, so he immediately knew that he had been fooled, but now he could only force the pass.

It was not until Li Shimin led the army to kill from the flank, and an unknown number of Tang troops appeared behind, that Dou Jiande hurriedly commanded his men and horses to retreat. But it was too late, he was chased by the Tang army for more than 30 miles, killed 10,000 people, captured 50,000 or 60,000 people, and all the other horses fled, and Dou Jiande was also captured alive.

Li Shimin said to Dou Jiande: "I originally only planned to attack Wang Shichong, but I didn't expect you to treacherously attack me from behind." ”

Dou Jiande's frightened legs trembled and said, "I'm afraid that I'll have to trouble you to go to Hebei and Shandong, so I'm here to send someone to the head." ”

Li Shimin and the generals laughed, Li Shimin brought Dou Jiande to Luoyang City, Wang Shichong saw that the reinforcements were hopeless, the people of Hangzhou had changed banners, and Li Tang unified the world The general trend has been decided, so he led the civil and military officials to open the city and surrender.

At this point, coupled with the fact that Luo Yi, who occupied Yanyun, had descended to the Tang Dynasty last year, the Tang Dynasty unified the north and south of the river, and a unified empire was presented to the world.

Li Shimin made immortal contributions to the Tang Dynasty, Li Yuan had no seal, and he was not ready to change the prince, so he had to appoint Li Shimin as the general of Tiance and open the Tiance Mansion to comfort the second son who had made supreme contributions to the Tang Empire.