[@Didgeridont]

That is the most likely scenario, that most if not everything we are legitimately concerned with would be intercepted or disabled before it could land on target - assuming it could even do so at all given just how complex the ballistics are, let alone the required nuclear physics. The only way to inflict any real damage would be a massive attack, perhaps in conjunction with it, but there would be no real point to do so because of the retaliation received; the whole northern peninsula becoming one giant swath of angry allied forces and assured global condemnation in its varied forms beyond the usual received.

Nuclear deterrence is alive and well, even today.