i was reading about the chinese civil war, and i was thinking why didn't the chinese communists ally themselves with the Soviet Union, together they would have been unstoppable, could somone explain that to me

Thanks

It's sort of like Catholics and Protestants getting together. They were both communist, but different brands.

don't forget the racial issue. both russians and chinese consider themselves to be racially superior to the other.
and they didn't trust each other. nixon used that to play them of each other when he visited china and then the ussr. nixon was brilliant when it came to forign policy. he exploited their mistrust and in doing so caused them to mistrust each other more.