Before the Battle of Chengpu, Chu not only crossed the Hanshui River and the Yangtze River, but its influence almost reached the Yellow River basin. In terms of quantity, it has more land, troops and subordinate countries than Jin State. At the beginning of this war, the Jin army retreated 90 miles, which was verbally said to be a promise to carry out, but actually reflected that the Chu army was in an advantageous position at that time. On the surface, the end of this war should be Chu's victory and Jin's failure. At that time, Yuzi and other generals estimated it like this.
However, the fact is contrary to this estimate. As a result of the battle of Chengpu, Jin, which was originally at a disadvantage, won. Why did Jin Can defeat the State of Chu? The reason for this is the following：
First, the ruling clique of Jin State headed by Jin Wengong has the determination to be competitive and establish hegemony. In order to achieve this goal, they have made many political and military preparations. Politically, Jin Wengong can pay attention to winning the hearts and minds of the people. For example, internally, he not only used harsh laws to safeguard his rule, but also paid more attention to "educating" the people, and naturally won the people's favor accordingly. Externally, he not only mastered Zhou's trump card, but also made a general appeal to the governors of various countries with the slogan of "respecting the king and rejecting foreign countries", and was good at using the conflict of interests between Chu and Qi and Qin governors to win the cooperation of Qi and Qin countries in order to strengthen his own strength. At the beginning of the battle of Chengpu, Jin Wengong ordered the Jin army to retreat 90 miles on the pretext of keeping his promise and repaying the kindness of King Chu Cheng. This action itself also won the political initiative of 8 Jin Army. Militarily, he began to train the army as early as the year he returned to China and acceded to the throne (636 BC). In the next two or three years, the rulers and ministers of Jin took various measures to improve the morale and combat effectiveness of the Jin army. Even in the process of attacking Cao Wei and Chengpu, this kind of training was not ignored. Jin generals are not only brave, but also resourceful and resourceful. From a military point of view, the "retreat of the three houses" of the Jin Army is a planned and important step for the disadvantaged Jin Army to preserve its strength and stand by and defeat the enemy. In this way, the state of Jin avoided the decisive battle with Chu under unfavorable circumstances, and achieved the purpose of active defense and morale. In the decisive battle, the Jin army avoided the powerful enemy, Zhong Jun, and chose the weak two-wing attack, which made it occupy the local advantage. Won the first world war, and then the rest, finally won the battle, from local advantages to overall advantages. In addition, the Jin army also created the illusion of the enemy by erecting a banner, dragging branches and raising dust, and then attacked the enemy unexpectedly, causing failure and fleeing. This is also a reason why Jin Jun turned disadvantages into advantages and passive into initiative, thus finally winning.
Secondly, in the aspect of Chu, there are different views and opinions on the struggle situation in Jin Chu within the ruling group of Chu. On the one hand, the king of Chu thought that the State of Jin was too powerful to defeat it. On the other hand, he doesn't want to let Kim hinder the development of his hegemony and wants to compete with it. Therefore, when Yu Zi insisted on fighting the State of Jin, he did not resolutely stop it with luck. Yu Zi was determined to fight the main battle, but he underestimated the strength of the State of Jin, overestimated his own strength, was proud and underestimated the enemy, and was unprepared for this war. This contradiction and mistake in the strategic thought of Chu's monarch and minister is an important reason for the defeat of Chu's army. Secondly, although Chu unified the armies of several small countries such as Chen and Cai before the war, these armies were improvised, unorganized and ineffective. Yu Zi didn't correct it. In the decisive battle, he relaxed the strengthening of the left and right wings, so as soon as the war started, the wings collapsed immediately. Chu's tactics are not as flexible as Jin's. The Jin army concentrated its forces to attack its left and right wings, but the powerful Zhong Jun remained motionless, waiting for the Jin army to break its left and right wings one by one. In this way, their own advantages will gradually become disadvantages, and finally fail in an all-round way.
Before the Battle of Chengpu, Chu was in a state of prestige. Although Qi and Huan Gong once joined forces with countries such as Lu and Song to denounce them, they did not destroy their power. It was only after the first world war in Chengpu that the Jin army dealt a powerful blow to the Chu army and stabilized the political situation at that time. The hegemony of the state of Jin was also determined at that time.
The battle between Jin and Chu is a struggle between the exploiting classes, just like the war for hegemony between other countries in the Spring and Autumn Period. The purpose of both sides of the war is to compete for land, population and extort tribute. Whoever wins or loses will bring disaster to the people. Therefore, it is difficult for the warring parties to say who is the aggressor and who is the victim; Who is just and who is unjust. However, on the eve of the Battle of Chengpu, the Di and Rong tribes in the north still seriously threatened the countries in the Yellow River basin, and the forces of Chu, known as "Na Man", were also expanding northward. This is unfavorable to the countries in the Yellow River basin and the development of their economic and cultural life. After the Battle of Chengpu, the State of Jin not only forced the forces of Chu to withdraw southward, but also relieved the threat of the Di and Rong nationalities, so that the more advanced economies and cultures of the countries in the Yellow River Basin could continue to develop. In this respect, the victory of Jin Guo in the war still played a positive role in the historical development of the countries in the Yellow River Basin at that time.