Far enough North might be 20 miles North of the DMZ.
But there is such a thing as a clean bomb.
If we respond to North Korea, North Korea might fire 20,000 artillery pieces at Seoul, South Korea.
Estimates are 1 million dead from that.
There has to be a plan in place to take out 20,000 artillery pieces before 1 million people (in South Korea) are killed.
But again, I may posting rubbish -- it is an area I have no expertize. And going to GlobalSecurity.Org would take too much time.
Apologies if this sounds like a bunch of HOGWASH.
Artillery typically does not shoot that far.