Wu Dong is different from Cao Wei and Shu Han. Cao Wei had a son of heaven at that time. Although Cao Cao was called a traitor, people also generously used the son of heaven at that time to do a series of operations Liu Bei claimed to be a relative of the son of heaven. At that time, the emperor probably admitted it for political purposes, so it was justified. Wu Dong had nothing, and Sun Jian was only the dominant satrap at that time, but his blood relationship with the Han family was somewhat weak.
Soochow chose to unite with Liu Bei when Cao Cao was ready to respond, because the combination of the two weak ones would certainly resist the strong one. Since then, Monroe of Soochow has joined Cao Cao and stabbed Guan Yu directly in the back. After the stabbing, Liu Bei came with the army, both sides had their own injuries, and then quickly joined forces to guard against Cao Pi. Later, no matter what conditions Cao Pi said, most of Sun Quan would agree, as long as it did not involve issues of principle, such as sending some jewelry to Cao Pi, giving back a lot. However, when Cao Pi asked Sun Quan's son to be a hostage, Sun Quan quit and made excuses.
In fact, Sun Quan did some things when he marched eastward to Cao Wei, such as sending generals to encircle Wei to save Zhao, or to attract the attention of Cao Wei at that time, but the real army did not act, because this was Sun Quan's way of survival, and Dongwu's huge inheritance must have development goals. Balance is Sun Quan's means to develop Dongwu. In fact, to put it simply, the swing grass falls to both sides in the wind, and it costs a little interest to which side it falls.