World war three will not happen unless it's the United States that first attacks North Korea; China and Russia will conclude that the US is the aggressor thereby coming to the North's aid. But if the aggressor is North Korea, then the US will have all room and say on how to deal with Mr Kim.
I agree with you on that, and that's why kim's just throwing all barks and not really initiating any real attacks because crazy as he is, he knows the backlash of it. Even china and russia may not save him when the us and its allies start throwing bombs at nokor.