Beating back the Turkish invasion of Taiyuan, he was put on the agenda by Tang Gaozu. His goal is to enter the West Pass and capture Chang 'an. In order to avoid the Turks taking the opportunity to help Liu Wuzhou attack Taiyuan, he steadied the Turks humbly and promised to dedicate all the treasures gained from the siege to the Turks, who sold him a good horse. After stabilizing the Turks, Li and Li Yuanji also rushed to Taiyuan to meet, and the great cause of Li and his son was about to begin.

Gao Deru, the prefect of Xihe County, did not respond to Li Yuan. Xihe (now Fenyang, Shanxi Province) was on the only way to March into Chang 'an, so the army had to take Xihe before marching.

On the fifth day of June, Li, Li and Li were sent to attack Xihe. At that time, the army had not been established, and Li and Li had not been given titles. The army called them Dalang Kazujiro. Lang in the Tang Dynasty was equivalent to the son of later generations. At that time, Li was 28 years old, 18 years old. Because he was too young, he sent Taiyuan to ask Wen to join their military staff.

At that time, the army had just been established and had not been trained. Li, afraid of the difficulty of running the army, made a military law first, and set off after a little rectification. The two brothers lived with the soldiers, shared joys and sorrows, and rushed ahead on their way. Folk fruits and vegetables were harvested in June. They don't rob people like other armies, but they have to buy them with money to eat. If a soldier steals melons and fruits, Li He will pay for him, and they will not pursue the thief.

Along the way, some villagers sent fruits, vegetables and water. They all thanked them and gave them to the soldiers. Everyone who sees them is involved. Someone sent beef and wine, but they refused, saying that this was the law of the Sui Dynasty, and our rebels dared not. I have to say, these two brothers will buy people's hearts and shine on you better than their father. The soldiers were very moved when they saw this and their morale was greatly boosted.

At the gate of Xihe, Li and He went to the gate and told those who were not wearing armor. People outside the city want to enter the city, regardless of men, women and children, all of them are put in. Officials and people in the city have long wanted to take refuge when they saw that this army is so tolerant. Only Cheng Jun Gao Deru will never surrender.

On June 10, Li He ordered the siege, just put up the ladder, and the soldiers marched forward bravely. An official from Xihe led his troops upstairs, arrested Gao Deru and took him to Li and Zhai. Defeat the enemy without fighting.

Gao Deru once flattered Yang Di and called wild birds bears. Li Shimin scolded him and said, "In the past, you falsely accused Xiangrui to please him, which was tantamount to Zhao Gao calling a deer a horse. We are rebels and will never let people like Zhao Gao go. " So he only killed one person, Gao Deru, and the rest Qiu did nothing. On June 14, he returned to Taiyuan and captured Xihe River on the 9th. Li Yuan was glad to have two capable sons, saying, "If you fight like this, you can govern the country." .

This is the first battle between Li and his son. How many pairs of eyes are staring at Li He? Fortunately, both brothers are lucky. Although they are young, they are brilliant and polite, and they deserve to take the lead. The victory of the battle of Xihe boosted morale and strengthened the confidence of Li and his son in commanding Guanzhong.