Since the end of the cold war...
There is little strategic need for the US to be mired in Korea.
Maybe NK thinks that they can bully the US out of supporting SK and then just walk in and take over...
The situation is extreemly dangerous if that is the case.
I think that Japan will soon begin a nuclear program of their own. Actually, I think they already have one. And soon some information about it will mysteriously leak out... Maybe that's it: An accidental radiation leak occurs and Japan must unwillingly announce that it is building its own bombs.
Scott