Thanks for your level-headed and reasoned demeanor in this little exercise, Neubob. The question of the catalyst hasn't been talked about, as I hoped it would.
Nationalism, principles or ideology may sprout blinders and earplugs on the heads of people, but disagreements about money raises their fists. Things were going well with North Korea prior to the summary judgement of "axis of evil" status - visits by the South Korean president and Japanese Prime minister, an admission to kidnapping Japanese nationals with accompanying remorse and general thawing of the freeze.
Things were being patched up again during the 6-way talks and the agreement last year by North Korea to continue not developing nuclear weapons in exchange for a promise of non-aggression and to not invade Korea as Iraq was invaded was hailed as a stepping stone back on the path to quasi-normalizing relations.
Three days after the agreement was signed, international banks, under duress from the U.S. Treasury Department, began freezing North Korean assets and all international cash transactions of North Korea. It wasn't a focused measure on questionable accounts, it was a blanket seizure of assets intended to deny North Korea any international trade.
As hard pressed as North Korea is for hard cash, that was a declaration of economic war and slap in the face after all the smiles and hand shaking during the signing of the agreement. The tests we see now is the measure they took to display their anger at what they perceive as a double-cross.
The problem with perceptions of double cross, intensified with the multipliers of money and pride, is that it makes otherwise reasonable people go nuts. What does it do to the marginally sane? Osama bin Laden is just such an example of what happens.
Will shots be fired if attempts are made to board ships in international waters? I don't have any doubt at all. It's happened a few times in the Sea of Japan in the past few years, with all the North Korean sailors dying in the process.
How will the US or Japan respond if they are the one's shot at? I have no confidence that either government leaders are listening to the professionals who have spent a lifetime studying North Korea, or diplomacy in general.
The North Koreans have always been looked at by advanced nations as being clumsy in diplomacy, but it appears they are no more clumsy than any other country.
In conclusion, I think we're witnessing a textbook repetition of how wars began in our textbooks - money, nationalism, pride and stubborness.