Less than 20 days after Emperor Taizong Li Shimin ascended the throne, two Khans from East Turkic, Jieli and Tuli, joined forces to invade. Tang Taizong personally led six generals including Gao Shilian and Fang Xuanling to lead the imperial forest army in the city to resist the Turks.
Tang Taizong sent Li Jing and other four generals to lead hundreds of thousands of soldiers to attack the Turks separately. Li Jing was a well-known military strategist in the early years of the Tang Dynasty. He was proficient in the art of war and made many achievements in the Tang unified war. Li Jing first personally led 3,000 elite cavalry, set off from Mayi, marched overnight, and pushed into the Turkic camp. Jieli didn't notice it, and was shocked when he saw the Tang army appearing. The Turkic soldiers first became chaotic, and when Jieli saw that the momentum was not right, he secretly fled to the north of Yinshan Mountain. Fearing that the Tang army would continue to pursue him, he sent envoys to the Tang Dynasty to plead guilty, willing to surrender to the Tang Dynasty. So Tang Taizong sent his envoy Hongluqing Tang Jian and general An Xiuren to appease the Turks, and at the same time sent Li Jing to watch the Turks' movements.
Li Jing sent troops overnight, and at this time Li Shiji also led his troops to arrive. After the two discussed, Li Jing was the vanguard, and Li Shiji was the follower. Along the way, Turkic soldiers were caught as guides. At this time, Jieli Khan was receiving the Tang envoy, and when he heard that he was allowed to surrender, he was secretly proud when a soldier came to report: "The Tang army is only ten miles away from here." Jieli Khan was shocked and asked the Tang envoy angrily: "The Tang Dynasty promised me to surrender, but sent troops to attack. Is there any faith?" Tang Jian hurriedly said: "Khan, don't be suspicious. We are coming from Chang'an. General Li may not know it. Now we are going to stop it. Let him go back, Khan don't worry too much." After finishing speaking, Tang Jian and An Xiuren left the camp, rode their horses and whipped them away.
Jieli believed them, thinking that the Tang army would retreat in a while, but the Tang army was getting closer and closer, Jieli realized that he had been fooled, and hurriedly fled on horseback. Li Jing took the opportunity to rush into the enemy camp and captured tens of thousands of people. On the way to escape, he was caught by his subordinates and dedicated to the Tang army, escorted to Chang'an, and the Eastern Turks perished.
After the demise of the Eastern Turks, Tang Taizong did not kill the captives, but set up a governor's office in the original place of the Eastern Turks, and deleted Tuli who had surrendered as the General of the Right Guard, the King of Beiping County, and managed the Eastern Turks. General, stay in Chang'an. At the same time, many leaders of the original Turkic tribes have been appointed officials, and many of them still live in Chang'an.
After the Eastern Turks were pacified, the kings of foreign tribes from all directions came to congratulate them, and elected Tang Taizong as "Tian Khan", and said: "It is the custom of foreigners to respect Khan, and now we call your majesty Tian Khan. Khan." Since then, foreigners have called Tang Taizong "Tian Khan". Since then, people from all ethnic groups in the Western Regions and many countries in Asia have come to Chang'an to study the politics, economy and culture of the Tang Dynasty.