1) A successful launch will have little impact on Japan’s national security profile. Most of the fallout, as it were, will come down on the United States.The first, most likely outcome—after all, North Korea must have a lot of confidence in its rocket to launch it to such fanfare; the Iranian connection must be bringing clear, tangible benefits—is the most favorable one for Japan if you limit considerations to security issues in an actual sense (that is, the abduction issue is treated as a social interest story). It brings U.S. national interests more closely in line with Japan’s, and that can’t be bad for the latter. (I’ve commented before on the Japan-U.S. gap regarding North Korea’s nuclear program and its consequences.) The second outcome is the most damaging one for both allies, though Japan’s ruling coalition has far more to lose in terms of domestic politics. There are other failed launch scenarios, but I don’t think it’s worth the time to go over them.
2) A failed launch followed by a failed MD intercept, as Matt Dioguardi casually intimated in a comment to my earlier post, will significantly harm the defense system’s deterrent effect.
Finally, I think the launch will come later, rather than sooner. North Korea has the world as a stage; that hasn’t happened in a while, and they’re going to hold onto the karaoke mike as long as they can.*
* ADD April 5: I take this back. North Korea will launch at the first technically viable chance, since the window of opportunity is short.