Eastern Wu's approach not only did not destroy the rules of mutual restraint, but on the contrary, it was to uphold the principle of mutual restraint. The most important thing in the Three Kingdoms was balance, when Sun Quan and Liu Bei dealt with Cao Cao in order to balance the relationship between the three families, and now Sun Quan and Cao Cao to deal with Liu Bei were also to balance the relationship between the three sides. Eastern Wu united with Cao Wei, mainly because Liu Bei's strength at that time was too strong, and it had threatened the survival and safety of Eastern Wu and Cao Wei. If Sun Quan did not betray the alliance, once Liu Bei defeated Cao Cao, the next destination would be Eastern Wu. Judging from the comparison of strength at that time, Liu Bei had a great strategic advantage, whether it was Sun Quan or Cao Cao, there was a risk of being eliminated by Liu Bei.
Therefore, at this time, it was not Cao Cao during the Battle of Chibi who affected the balance, but Liu Bei, who had just risen.
After Liu Bei captured Yizhou, he had already accomplished his goal of owning Jingzhou and Yizhou. During the Battle of Hanzhong, Liu Bei crushed Cao Wei's main army, laying the groundwork for the next attack on Liangzhou.
At that time, Liu Bei's army had five tiger generals, Ma Chao had been operating in Liangzhou for many years, and Cao Cao had just been defeated and his strength had not been restored, and Liu Bei's capture of Liangzhou was within reach. Guan Yu's battle against Cao Wei in the Jingzhou area was gradually defeated, and it seemed that he was about to attack the central region of Cao Wei.
Cao Wei's side was very passive at this time, the Liangzhou side did not have much defensive strength, almost to give liu Bei, and Cao Cao in the central region wanted to move the capital and give up several counties near Xuchang to Guan Yu.
If Liu Bei had accomplished these two goals, the situation would have been very unfavorable for Sun Quan.
Sun Quan had already betrayed an alliance once in the twentieth year of Jian'an (215), when Liu Bei was not strong enough and was forced to give Sun Quan 2 counties as compensation. Once Liu Bei became the strongest force, even if Cao Cao could not be destroyed, it was still easy to destroy Sun Quan. Moreover, Guan Yu was in Sun Quan's upper reaches and was able to directly attack Sun Quan's weakly defended southern region. If Liu Bei sent troops from the three counties of Shangyong, he would soon be able to reach the center of Eastern Wu's rule by advancing by land and water, which Sun Quan did not want to see under any circumstances.
If Sun Quan remained silent at this time and allowed Shu Han to attack Cao Wei, the situation in the Three Kingdoms would soon change.
Once the Shu Han captured Liangzhou and Yuzhou, plus the previous Jingzhou and Yizhou territories, I am afraid that it would not be able to stop it at all. The shu han army itself was strong in combat, and the generals and strategists were all top-level people, and Liu Bei had always taken the unification of the world as the goal, and would certainly not allow the existence of Eastern Wu. At that time, even if Sun Quan wanted to turn his back on the alliance, he would not have this opportunity.
At this critical moment, Sun Quan chose to renege on his alliance agreement with Liu Bei and join forces with Cao Cao to attack Guan Yu.
After Sun Quan betrayed the alliance, he not only captured Liu Bei's Jingzhou territory, but also killed Liu Bei's general Guan Yu. After Sun Quan attacked Guan Yu, Shu Han began to decline and no longer had the strength to dominate the world.
After Guan Yu's death, there was a period of balance between the three kingdoms for more than forty years, whether it was Cao Wei attacking the State of Wu and the State of Shu, or the Northern Expedition of shu Han and the Northern Expedition of Eastern Wu, which failed to shake this pattern, until the destruction of the State of Wei and the destruction of Shu Han.
Sun Quan's betrayal of the alliance was indeed rather hateful, but considering the form at that time, Sun Quan was only for self-preservation. Liu Bei really gained power, and he certainly would not abide by the alliance. I don't know what you think, welcome to leave a message to communicate.