The North Korean wildcard: Japan

I feel like I repeat this way more than I should, but I'm a big proponent diplomacy that is spoken softly in the shadow of a great big damn stick. As we continue on with North Korea, I think we may be seeing the most affective big stick imaginable shadowing over North Korea and, to a lesser extent, China. That stick would be Japan:

Japan said Monday it was considering whether a pre-emptive strike on the North's missile bases would violate its constitution, signaling a hardening stance ahead of a possible U.N. Security Council vote on Tokyo's proposal for sanctions against the regime.

Japan was badly rattled by North Korea's missile tests last week and several government officials openly discussed whether the country ought to take steps to better defend itself, including setting up the legal framework to allow Tokyo to launch a pre-emptive strike against Northern missile sites.

The last thing either of the Koreas or China want is to see Japan start fiddling with it's 'defense only' military policy. This may be just the big stick that makes the soft speak more effective.