Just a random thought before I get back to work on the house:
It was the US cut-off of oil (well, and scrap metal) to Imperial Japan that "forced" Tokyo into attacking Pearl Harbor, in the vain effort to get us to negotiate some sort of settlement recognizing their interests in China and elsewhere.
We've now cut off much of North Korea's oil -- the free stuff they've been getting from us since the 1994 agreement is about all that cash-strapped nation is able to afford.
As Steven Den Beste wrote, their clock is ticking. Pyongyang, like Tokyo in 1941 and Germany in 1914 is "an army with a nation attached to it." What happens if that army thinks its lifeblood is choked off?