Realistically what is the chance of patriot being able to intercept an intermediate range ballistic missile? The things go higher than short range systems like Scud, and I assume come down with much higher velocity as a result. If North Korea were to fire a large salvo of missiles, with the nuke on a latter one (or even developed MIRV's), I would not bet on Japan shooting it down.

First I doubt NK could muster a lot of missiles. A single battery of PAC-IIIs can have 8 launchers with 16 missiles each for 128 missiles. Sounds like they are deploying more than 1 battery - "One of the Patriot (PAC-3) missile air defense artillery brigades would be deployed at Fuchu Air Base in Tokyo. The new Patriot missiles can intercept and destroy ballistic missiles, cruise missiles and enemy aircraft." Can't give a probabilty of a kill for each round fired, but they have become much more sophisticated then the earlier patriots. Not much talk about SCUDS in GWII, as they didn't have any cameras on them like GWI. I can give you the probability of NK building it's own nuke warhead and mounting it on it's own missile, < 1%. Nuke warheads are hard to shrink to missile size, and building a reliable missile is also hard. The kind of weapon they are like capable of building would be better delivered by ship or airliner. Now if they have had help from say Russia the deal is off. But I don't think Russia is that nuts. Anyone else? I don't know.