N. Korea pops a Nuke about 10-20 Kt range. Japan is furious and I do not think it will take them long to develop their own nuclear program. South Korean forces went on high alert. Even China is mad. I think the Great Leader thought he was out of the limelight too long and wanted to get the world's attention.
Of course N. Korea is a proliferator of missile technology and it will be interesting if/when we find out if Iran sent some people to watch/help with the test. Watch the news the next few days folks.