Bullshit. N Korea is trying to pull the insanity case of unstable military decisions so everyone will think twice and back down. There is no way N Korea will attack S Korea unless they want the entire global community to collapse them. Naval ships from different countries will be in the area, China will move troops to the border, US will begin air patrol, etc.
N Korea will become the most isolated country in the world.
it probably already is one of the most isolated already....
i would imagine the reaction time of the US having flights flying CAP would be less than an hour if N. Korea made any aggresive move towards the south.
i would guess inital US military strike if N korea crossed borders would be within inital 30 minutes.