The policy of strategic patience has ended. –Secretary of State Rex Tillerson
Donald Trump and Kim Jong-un are both unpredictable and therefore dangerous. Rex Tillerson is new to his job. Tillerson says US policy has failed in Korea, but I think not–war has been avoided for fifty years which is hardly failure. Defense Department and State Department experts may know how Kim is likely to respond to threats, but are Trump and Tillerson listening? How much does Kim know about Trump? Probably not much.
War in Korea would be a humanitarian catastrophe. Seoul is a city of more than ten million; war would likely cause panic there. Tokyo might be attacked. War is never easy or cheap.
What was accomplished by war in Afghanistan? What good was done by war in Iraq? Who anticipated the damage done by unexpected weapons, IEDs for example? What good could possibly come from war in Korea even if it caused the rapid collapse of the North Korean government? What is our exit strategy? What might the Koreans do to thwart our plans?