NK is threatening with nuking US

[Anomalocaris]

um . . .

there is a truce in effect from the Korean War, but that's it.  State of War exists on paper at least, and as such, I'd say while it might not be too smart to fire at 'em, any aircraft in South Korean airspace might be plausibly subject to attack.

And it is quite common for North Korea to fire artillery shells South Korean troops on the ground inside South Korea. It happens at least once every couple of years.

North Korea also routinely send infiltration parties into South Korea. They are pretty well practiced at this. Most of these are probably not caught. One could expect heighended efforts to send more infiltration parties if they really anticipate conflict.