Due to its partial security, the Eastern Jin always faced threats from the north. Zu Ti, Yu Liang, Yin Hao and Huan Wen all went to the Northern Expedition successively, but none of them succeeded. In 404 AD, Emperor Wu of Song rose up and defeated Huan Xuan, who usurped gold and proclaimed himself emperor. The following year, Emperor Jin 'an was restored to control the political affairs in the Eastern Jin Dynasty. At that time, the internal contradictions of the ruling group in Southern Yan became increasingly serious, and Murong Chao's treacherous credit and heavy taxes on killing virtuous people aroused strong public resistance. For the strength of the rulers, Emperor Wu of Song decided to move north. In order to fight against Southern Yan, Emperor Wu of Song raised his voice, so he wanted to direct the Northern Expedition.
In February 409, Southern Yan army invaded Huaibei, which just gave Emperor Wu a chance. He wrote to the emperor, asking for the Northern Expedition. After being approved by the imperial court, he quickly sent troops and arrived in Xiapi in May.
Before and after the two Northern Expeditions, Southern Yan was destroyed, the Northern Wei Dynasty was broken, Qin was lost, Shandong, Henan, Guanzhong and other places were recovered, and Luoyang and Chang 'an were recovered. Although Chang 'an was recovered more than a year later, the east of Tongguan, the south of the Yellow River and the whole of Shandong have been included in the territory of Liu and Song Dynasties, and the Jianghuai basin has been guaranteed.
Comply with the development trend
Southern Yan, originally a small separatist force split by Houyan, ruled only to the east of Jinan, Shandong Province, and to the north of Zaozhuang to the coast of Bohai Sea. It was a small country in the late Sixteen Countries of the Eastern Jin Dynasty. It has neither enlightened political measures nor social and economic development, but closed separatist rule and oppression. People in the north of China have long hated this chaotic situation of separatist regime and incessant wars. In particular, the officials who moved to the Eastern Jin Dynasty with the Northern Jin Dynasty had a strong desire to unify the North and return to their hometown. So,
Emperor Wu of Song initiated the Northern Expedition, which adapted to the demands of the people at that time, and made Jinshi present a situation of "China people's great satisfaction" wherever he went. This became the unique political advantage of the Eastern Jin Dynasty.
Powerful war strength
Since the Jin Dynasty established itself as the capital of Jiangnan, although there have been numerous civil strife and wars of different scales, it has basically maintained the unity of the country, far from the bleak and broken situation of disputes among many countries in the north, the chaos of war and chaos, and the serious destruction of social economy. After Emperor Wu of Song came to power, he took measures to reduce taxes and develop production. Coupled with the natural economic and geographical conditions in the south of the Yangtze River, the economic strength of the Eastern Jin Dynasty gradually increased, and a large number of powerful troops such as cars, infantry, water and riding were trained and recruited. This army is obviously superior to Southern Yan Army in quantity and quality, which provides a solid material foundation for defeating Southern Yan.
Emperor Wu of song lived in Chang' an for two months, and there was an urgent report from Jiankang that "the left servant shot Liu." Emperor Wu of song is very worried. He was afraid that he would leave the court for too long and his power would be taken away by others. So he returned to Jiankang, personally took charge of state affairs, and sent some cronies to hold important positions. Liu Yu had planned to go to the Northern Wei Dynasty in 422. As a result, in May 422, Liu Yu died of illness and the Northern Expedition was cancelled. The great cause of the vigorous Northern Expedition was a flash in the pan after all.