China is obviously the key to this. Trump can threaten all he wants but is tied by the potential carnage to be inflicted on S. Korea by the North. Even 'Mad Dog ' Mattis, his secretary of defence can not be mad enough to risk it. Maybe Mattis and his extended family should be moved to a posting in Seoul till all this cools down. Quotes from Mattis:- I come in peace, I didn't bring artillery, but I'm pleading with you with tears in my eyes, if you fuck with me I'll kill you all. (To Iraqui leaders soon after start of the Gulf War.) Be polite, be professional, but have a plan to kill everybody you meet.( To the marines in Iraq).