There's never a threat, no matter how illusory, that the war heads won't demand an answer to.

North Korea doesn't have ICBM's. And even with an all-out engineering effort, North Korea won't have them for a long time. Prior to any mooted ICBM's becoming a credible DETERRENT, a great deal of testing of the missiles will have to take place. Giving the world adequate time to intervene, if necessary.

The fact is, the effectiveness of even North Korea's short and medium range missiles are unknown, including to the North Koreans themselves. It's not as if NK is going to win a war with them.

I emphasized the word DETERRENT above, because that's what ICBMs are. They have little or no value as a weapon of aggression, because their first use invokes total destructive retaliation. ICBMs, and nukes in general, are a deterrent to being attacked. Nukes have only been used once, and never in a first strike. This has been the reality throughout the 70 years of their existence.