Richard Haass, President of the Council on Foreign Relations, has been thinking aloud:

Imagine it is 2020. The director of the CIA requests an urgent meeting with the US president. The reason: North Korea has succeeded in making a nuclear bomb small enough to fit inside the tip of an intercontinental ballistic missile capable of reaching the continental United States. The news soon leaks to the public. High-level meetings to devise a response are held not just in Washington, but in Seoul, Tokyo, Beijing, and Moscow as well.

This scenario may seem unreal today, but it is more political science than science fiction. North Korea just carried out its fifth (and apparently successful) test of a nuclear explosive device, doing so just days after testing several ballistic missiles. Absent a major intervention, it is only a matter of time before North Korea increases its nuclear arsenal (now estimated at 8-12 devices) and figures out how to miniaturize its weapons for delivery by missiles of increasing range and accuracy.

It is difficult to overstate the risks were North Korea, the world’s most militarized and closed society, to cross this threshold…

Yep. Which is just another reason for being worried about a President Trump.