I read somewhere that the NKPA has the largest SOF contingent in the world. I know most of it is akin to what we have in the Army Rangers (aka, big raids on airfields and the like) but the fact is, Japan is probably riddled with these folks, and I am sure some submarine delivered visitors arrived just before the tests. I think when all heck breaks loose, and I think it will soon, we're going to see the NK version of the old Soviet Spetsnaz go to work. God, I hope the Japanese are ready for that. I would not wish that on anyone.
http://www.globalsecurity.org/wmd/library/news/dprk/1996/kpa-guide/part03.htm
Here is where I read the info on that last post. Chilling stuff.