North Korea is in a dangerous circumstance right now. The leader is dying, and to pass on his reign to his son, he must be at war.
Keep in mind that post World War 1 germany was extremely poor due to hyper-inflation---which birthed the most aggressive imperialist military-industrial agenda in the history of mankind. They didn't treat their brothers so well, as we all know.
When the people have nothing to lose and everything to gain by going to war, that means they're backed in a corner.
I believe Obama would retaliate... but we're already stretched thin.