Comment by aguaviva

By the time China entered the war, the invasion was already over.

I don't see any substance the point you're trying to make here. One could try to say, "China was only trying to preserve North Korea's borders prior to the invasion". But once it pushed further south, into South Korea proper -- it was joining the invasion. There's nothing to debate here.

1) to make sure China was not invaded as MacArthur intended

And this just makes no sense at all.

MacArthur never intended to invade China, and didn't even start making noises about bombing China until after the it joined the war effort.