If we were confronting a relatively normal leader, I wouldn't give it a second thought. The fact that we're confronting a despot, throws the whole thing into a different, dangerous, situation. Un is unpredictable. Are we bluffing? Depends on him. If he does the unthinkable, it's game over. I hope when it's over we'll look back on it as a bluff. Any of the other scenarios, including his army attacking S. Korea, is a nightmare.