"Trump tweets this advice to Secretary of State Rex Tillerson: 'Save your energy, Rex, we’ll do what has to be done!'”

I have a couple of questions:

Does the simple-minded Trump think that a schoolyard good-cop-bad-cop strategy will work in actual grownup diplomacy with this dangerous regime?  And second, does South Korea have any say in what this absolute nincompoop might do and thereby possibly destroy their country in a catastrophic war?