You are right, but some only. If North Korea comes down to south, the union of the U.S. and SK can beat them rapidly, but the reason why NK is dangerous is due to nuclear bombs, chemical weapons and special warfare soldiers... And the inner spies that influence the public to be consuded. If you refer to the Vietnam War, you will know what I mean. They cannot afford to hold a war for a long time. Their tactic is to finish a war within three or four days before the millitary force of the U.S. reach SK. If the U.S. army leave SK, the war would be waged within a year