You found a heart!
Also remember that countries aren't isolated from the rest of the world. You can't start a war against someone else on your own as if this were the early years of the Cold War. As soon as NK dared to do something, they'd discover that a ridiculously huge amount of important countries in the world, starting with China (you know, the one that keeps them alive in general), would retaliate against them.
There is no Soviet Union to support them, and China is no interested on any nuclear wars going on in his backyard, I can guarantee you that.