Role of North Korea
North Korea was in the middle of the whole Korean War, since it is apart of Korea. It had been the side of Korea that was towards the communist's side, wanting to also spread communism throughout the rest of Asia and had begun with its opposite part, South Korea.
The role of North Korea was of course huge, it was one of the two main in the war. If North Korea wasn't apart of it, there wouldn't have even been a "North Korea' or "South Korea" it would just be one big Korea, and they would be fighting against the other communists like China or the Soviet.