The Sinking of the Cheonan

It's pretty certain, by now, that North Korea sank the ship. It's reasonably certain that this was done at the command, if not the concurrence, of the dictator of that nation.

It is less than clear what happens now. China is very reluctant to do anything to upset the North Koreans. South Korea will take measures short of war, for they have far more to lose in a conflict.

I'd look for an indication that China and Russia are tightening border security with North Korea in order to stem a tide of refugees. That may indicate how bad they expect things to be.