North Korea sinks South Korean war ship. North Korea shells South Korean Island. North Korea refining uranium and building atomic bombs.
What can be done about North Korea? Not much. Even China, their only important ally and key supporter, can’t get a handle on what to do about North Korea. The only reason China really cares what becomes of them is because the collapse of North Korea would bring a western-oriented, U.S-allied and united Korea right to their doorstep on the Yalu river. Allied proximity to that border during the Korean war was what brought the Chinese military into it.
Diplomatic options don’t work with them, since they later break the deal and try to extort more concessions. Pinprick military options would be exceedingly dangerous, since the North seems to invite a provocation to resume the Korean War (no peace treaty has ever been signed, so technically the war never ended).
Militarily, I only see one option: An all-out, multi-pronged pre-emptive strike which would destroy any capacity they might have to respond in a meaningful way.
Anything less would be worse than useless. A ‘limited proportional response’ would only invite a violent and bloody war that could drag on for days, months or years.
Truly, North Korea represents today’s clearest example of an international no-win situation.