This is a legitimate concern with the "young" nuclear powers, like India and Pakistan. Their detection technology is less mature; their command-and-control systems are less mature; there's a higher level of tension between the two. Neither country is incompetent or hungry for war, but it's worrying to me. I'd expect them to behave rationally, but if the timing happened to coincide with a particularly combative episode, things could get out of control. I'm not even going to speculate about how North Korea might react; they're a total wildcard.