Less known to most folks is there was a Second
Korean Conflict from 1966-1969:
https://en.wikipedia.org/wiki/Korean_DMZ_Conflict_(1966%E2%80%931969)
Even less known is the simple fact that the 1950-1953 Korean war was never declared over. We have been and still and are at a legally declared state of war with NK since 1950.
I believe this gives a US president the legal right to flatten everything from the DMZ to the Yalu river. Not that it would be a good idea, but under the War Powers Resolution of 1973, he has the authority.