At the end of the Eastern Han Dynasty, it was reduced to the chaos of the Three Kingdoms, and when Shu Wei and Wu divided the world, what method did they use to divide the borders? Since ancient times, many dynasties like to demarcate the Yellow River yangtze river, and the Three Kingdoms of Eastern Wu and the State of Wei are just separated by a Yangtze River, according to military superiority, the Yangtze River is the best thing to do, but why is the State of Wei unwilling to use the Yangtze River as the dividing line between the two sides?
At that time, the State of Wei gradually rose strongly, because of the Han imperial family of Liu Bei of the State of Shu, he organized a large army to set foot in the territory of the State of Wei to support the Han Dynasty, which made the State of Wei uneasy inside and outside the country for many years, so it shifted its strategic focus to the other side of the State of Shu, and Eastern Wu, although it was also an enemy, was ranked in a secondary position. At that time, Liu Bei mobilized the main army in the Jingzhou County, and also sent guan Yuzhen, the god of war, to guard the Fortress of Jingzhou, because this city was an important strategic place for the Northern Expedition of the Shu Army, and the State of Wei knew the importance of Jingzhou and understood that if the State of Shu wanted to restore the Han Dynasty, it would have to die to protect Jingzhou, so Cao Cao turned the southwestern region of the State of Wei into an important defensive point and heavily guarded it to prevent the Shu army from invading.
At that time, the State of Wei and Eastern Wu were indeed separated by the Yangtze River, but Cao Cao suffered a big loss in the Battle of Chibi, the so-called eating a long and wise, then take the Yangtze River as the boundary, then the water army of Eastern Wu can exert its advantages to crush the Wei army and then invade the border, so the State of Wei will definitely not allow itself to be in a passive position. Therefore, even if Eastern Wu wanted to use the Yangtze River as a boundary, Cao Cao could not agree, and some reasons were that the Wei Dynasty soldiers were mostly natives of the north, they did not know the nature of water, and some people would be seasick and vomit, because it was not conducive to water warfare. Soon the Shu army aggressively attacked the southwest of the State of Wei continuously, and Cao Cao did not want to entangle with Eastern Wu any longer, so he gave in, voluntarily abandoned the Yangtze River, ordered the army to retreat to the Qinling Huai River, and then continued to retreat north to a desolate area a hundred miles away from the north bank of the Yangtze River, where he built fortifications to block the northern invasion of the Wu army. Therefore, the actual dividing line between Wei and Wu at that time was a hundred miles north of the Yangtze River.
Later, the wei-Wu dividing line changed with the strength of their respective countries, and after the Wei state gradually became stronger, it launched a war of invasion of Wu, so the battle line was pulled to the bank of the Yangtze River, and when the Wei army retreated, the dividing line automatically retreated to the place where the Wu water army could not fight. After many years passed, due to the repeated failures of the Northern Expedition of the Shu army, Zhuge Liang fell ill and died in Wuzhangyuan, the backbone of the Shu state was almost dead, and the greatest threat of the Wei state was eliminated, so he turned around and prepared to deal with Eastern Wu.
At that time, the Wu state had the title of "the land of fish and rice", mainly using the dangers of the Yangtze River as a cover, and their strength in the later stage of their development was not as good as before, and they could no longer resist the Wei army, so they could only give full play to the advantages of the water army troops as much as possible, mainly fighting water battles, and the Wu army did not dare to go too far away from the Yangtze River no matter how they fought. For the most part, the State of Wei fought against Wu Bing within a hundred miles of the Qin Tombs on the Huai River, which later became the dividing line between Wei and Wu.
For the regime in the Jiangnan area, if it starts a battle on the Yangtze River front, it is actually a great threat, and if it fails, then the enemy soldiers will quickly cross the Yangtze River and enter the city of Nanjing. This is also a complete loss to What Eastern Wu said, so they also tried their best to fight in the area north of the Yangtze River, and fighting the Yangtze River water war was only a helpless move, because this was equivalent to the last defensive line of the Wu State, although the water army of Eastern Wu was very capable, if a defeat would mean that the overall situation had been decided, and the destruction of the country was only a matter of time.
It is said that King Wu's idea was very strange, he knew that his army could not defeat the State of Wei, but still often sent troops to harass the borders of the other side, and always sent people to rob the cities in the northern region of the Jiangsu Province, not only ordering soldiers to loot property but also robbing people, because at that time, although Eastern Wu was rich in fishing and rice, but because of the lack of population, the overall development of the country was very slow, so King Wu wanted to grab more people to go back to development in an attempt to enhance the national strength of Eastern Wu.