Cliff, I agree with you that Japan is an important piece of this. David Frum said the same thing in his New York Times piece today:

Encourage Japan to renounce the Nuclear Nonproliferation Treaty and create its own nuclear deterrent. World War II ended long ago, and it’s time to put an end to the silly pretense that today’s democratic Japan owes a burden of guilt to today’s rising China. A nuclear Japan is the thing China and North Korea dread most (after, perhaps, a nuclear South Korea or Taiwan).

But my (shallow) understanding of Japanese political culture is that it changes only slowly and any decision to go nuclear will be a long way off, probably too far off to play much of a role in the current crisis. But it certainly wouldn’t hurt to begin talking about it.

Here’s my column on the North Korea business.