If the state of Jin had been divided into southern Jin and northern Jin, the dividing line would have been very long. The adverse effect of the long demarcation line is that military bases and areas with complex population will become very large and the country will be difficult to manage. After all, border areas are the most difficult to manage and unify. From the map, the whole population transfer direction has traces of the Yellow River basin moving to the Yangtze River area. The main reason is that there are many disasters in the Yellow River, which is not easy to control, while the Yangtze River is relatively suitable for people to live and farm in flat plain areas. At that time, the capital of the State of Jin was called the Western Jin in the Central Plains and the Eastern Jin in the south of the Yangtze River.
Song is the opposite. The capital of Zhongyuan was called the Northern Song Dynasty, and the capital of Jiangnan was called the Southern Song Dynasty. However, this is very different from the state of Jin. First, because the humanities were different at that time, and second, the territory was different. During the Three Kingdoms period, there was a place called Jiangdong, but it was not Jiangdong in Hugh, but its real name. At that time, Xiang Yu led 8,000 soldiers to fight in Jiangdong. From the map, the Yangtze River divides the whole area into Jiangxi and Jiangdong.
However, there is a difference between Jin and Song. At that time, the capital of the Western Jin Dynasty was located in Luoyang. However, due to the decline of national strength, in order to change the country's fortune, their king believed Feng Shui master's words and said that he would move the capital to Chang 'an. From the map, Luoyang is indeed in the northwest, and Nanjing is in the southeast of the south.