The Norks and their nukes

The Economist ran a cover story about the need to do something about North Korea's nuclear program. They went on about weakness and craziness in the Kim regime.  Like it might be so crazy as to not be deterreable. The Norks have a missile operational today with enough range to hit all of South Korea and all of Japan.  They have missiles under development with enough range to hit the western US.  They managed to launch a satellite which means they have a missile that can reach anywhere in the world.  Might not have the throw weight to loft a nuclear warhead, yet.
   The Economist claims that the Bill Clinton administration considered an air strike on the Nork's nuclear facilities, but Clinton backed off,. fearing that it would touch off a second Korean war.  I never heard that story before.  There has been some talk that the Norks have dug in so deep that even our 15 ton Massive Ordinance Penetrator bomb couldn't take 'em out.
   The Economist does acknowledge that non-military ways of pressuring the Norks pretty much don't exist, especially as the Chinese like having the Norks as a buffer state between them and the South Koreans.  The Chinese are sending enough food and fuel to North Korea to keep 'em alive.  The Chinese fear the Kim regime is shaky, and that any serious pressure might cause it to collapse.  The Chinese don't want that to happen, cause the likely result is the South Koreans take over from the Kim regime, giving the Chinese a pushy, industrialized competitor, who is hand in glove with the Americans, right on their border.
  Best the Economist can suggest is installing anti missiles, THAAD and Patriot.  They compute that such a two layer defense, each layer having a Probability of kill (Pk) of 70% would yield an overall effectiveness of 90%.  Not bad, but not very reassuring when you think about how bad just one nuke can be.
   Of course Aviation Week doesn't see things quite that way.  They have reported that each of the Nork nuclear tests had a yield of about one kiloton of TNT.  That's so weak that most people call it a fizzle.  So maybe the Nork's don't really have nukes, yet.