Re: Next steps...
Shipping containers aren't a very reliable method. And take lots of advanced prep. So they're a good covert first-strike option, but of limited use as a second strike deterrent.
Particularly as North Korea isn't plugged into the global shipping network, and their ships get monitored, as they're often carrying weapons to places people might not want weapons sold to. So they might have to ship their container via land through China, which might annoy the Chinese government somewhat...
At times of high tension, that threat massively diminishes, as none of North Korea's ships are going to be going anywhere un-watched.
You could of course pre-position one in a third country, but that requires giving a lot of control of a precious national resource (a warhead) to an independent group you can no longer shoot. And has a high risk of getting discovered.
Whereas a working ICBM on a train or truck that can be hidden gives second strike capability, even if the regime has been destroyed.
Biting the hand that feeds IT
