Maybe they’re bluffing, maybe they’re not. Good luck!
Seriously, if the UN imposes Chapter VII, why wouldn’t Kim move on Seoul? What’s left for him to lose? Even the doves in South Korea admit that the sunshine policy’s failed. If the Security Council tightens the screws, what’s to gain by waiting around? Japan doesn’t have nukes yet; our military is overextended and morale is low. The NorKs won’t see a moment this golden again. Why not seize it?
Update: And if they do, is it really our problem?
Update: Japan won’t blink.