The problem with trying to stop North Korea, Iran, etc. from developing nuclear weapons is this: When in history has a piece of technology, once invented, not become increasingly cheaper, more readily available, and more commonly built and modified by reasonably intelligent people the world over?
I don't even understand what it means when I hear things like "so-and-so has the capability to build a nuclear bomb, but has not yet figured out how to mount it on a ballistic missile." Don't they have a schematic? How have we kept this secret between us, the British, the Chinese, the French, the Indians, the Pakistanis, the Russians and the Israelis all these years?
Granted, I know next to nothing about the mechanics of nuclear weapons. But I do know that technology gets more and more widely disseminated. Always.
That's why I think our number-one military priority should be a nuclear-missile shield, just like good ol' Reagan talked about back in the day.