Why did China enter the North side of Korea during the Korean War?

Question

I need it for a report

Answer 1

Because it was in there interest to do so.

China and NK never had nor have a really
good relation. Kinda like the cousin you don't
really like but for some mean twist in fate he's
in your family.

North Korea, as China, was on the "EAST" side.
After the war turned in favor for the South China
realized that a western controlled Korea would
interfere with their interests in that part of the world
and that weapon supply wouldn't prevent this.

With foresight this was a pretty clever move. With
hindsight it turned out to be a really bad idea.

Answer 2

To prevent North Korea from losing the war.

At that point in time the NK was in full retreat and they had lost almost their entire army and country to UN forces. China didn't want their surrogate to lose the war, which would have set back their efforts at increasing the number of communist countries.