Did you ever see a nuclear reaction modeled with mouse traps loaded with ping-pong balls?
It's on YouTube.
But with regard to World War III ... I think that this simulation is very, very applicable. When nukes start flying countries will be forced to launch whatever they have, against those who are responsible and against those who haven't launched yet. There won't be time to investigate. NK can become an initiator of such a chain reaction.
The World War III is not a certainty, of course, even if NK manages to set up a few explosions in a few countries. (If they do, I'm pretty sure they will do it by smuggling a nuke in, not by flying it on a poorly made rocket.) It all depends on rational thinkers in governments of victim countries.