Li Yuan and his clan defeated their rivals in the Sui Dynasty (581-618) to become the founder of the Tang Dynasty. His son was named Li Shimin (599 to 649). Li Shimin killed his two brothers and led an insurrection against his father in the year 626 to depose him to become the ruler. He was a famous and long-lived emperor and is called the Emperor Taizong (唐太宗, Tang Great Religion). Maybe he is called this because he promoted Mahayana Buddhism in the Tang Empire. He also promoted Nestorian Christianity. During his reign, the empire prospered. He is thought to be one of the great emperors because he expanded the Tang Empire and the government stabilized during his reign of 23 years.
Emperor Taizong was the second emperor of the Tang Dynasty of China. He ruled from 626 to 649. Before he deposed his father to become an emperor, he played a role in defeating the Sui Empire’s troops and helping his family rule the empire. He was said to be good with handling weapons and was a good fighter in battle.
Under his rule, the territory of the Tang Empire expanded and prospered. Like the Qin Empire, the Sui Empire that his family conquered was short-lived, but the Sui rulers undertook a lot of expensive construction projects at great expense and by making hundreds of thousands of people work. The Tang Empire inherited the infrastructure that was developed by the Sui rulers, and once the conflicts in the empire were settled, the economy started to flourish. The large Grand Canal system made transportation between northern and southern areas more economical so products were transported more easily and cheaply. Silk Road trade with Western areas increased as Tang armies defeated people in the northwest. This trade prospered the Tang economy, and the cultural and religious influences changed the culture.
His policies were to expand the empire in the northwest and to spread Buddhism and Nestorian Christianity. His father was against religions he considered foreign such as Buddhism and Christianity. But the Taizong Emperor supported the Nestorian religion. He met a Nestorian in Changan in 635. He said that he found the religion acceptable and good and wanted it propagated. In 638, Taizong issued an official declaration protecting the Nestorian church and had a church built. In 639, he built Buddhist temples at the site of recent battles. Under his rule, Christianity became a minor religion in the empire.
He wanted to conquer the northwest from the start of his reign. When he killed his brothers as they were entering the palace and deposed his father in the year 626, a Gokturk leader named Qaghan led an army to Changan to attack the Tang rulers. Li Shimin agreed to an alliance with Qaghan and also agreed to send tribute. However, there was extremely severe weather and strange natural phenomena in the northwest in 627 and 628. In 628, Taizong wrote that there was frost in the middle of the summer. Much of the Gokturks’ livestock died. This natural disaster severely weakened the Gokturks. The Uighurs in the area rebelled against the Gokturks, and the Tang army defeated the Gokturks in 630. In this way, the Emperor Taizong became the ruler of the Gokturks. The Tang Empire added of Central Asia and the lucrative Silk Road trade route was reopened. Traders and missionaries including Buddhists and a Nestorian named Alopun followed the Silk Road trade route and arrived in Changan that was the Tang capital.
To the west and north of the Tang Empire, there were other empires called Tuyuhun, Tufan, and Tibet. In 635, a Tang army defeated the Tuyuhun. They also defeated a Tufan army in 638. But they were not able to defeat the Tibetans. The Tibetan Empire was a major threat to the Tang Empire throughout the reign of the Tang Dynasty. In the decade of the 640s, Li Shimin sent large armies against the Korean Goguryeo who had earlier defeated huge Sui armies. One Sui army that they defeated was said to have had 1.5 million troops. Under Li Shimin, the Tang rulers couldn’t defeat them either. They defeated his campaigns. Li Shimin died in the year 649.