But I don't think any country would stand by and let another country be annihilated without doing anything. Nuclear armageddon has never happened before, and it's very unlikely when you have two countries so different in power like the USA and the DPRK. There hasn't even been a standoff yet. Many people say the closest the world's ever come to nuclear war was during the Cuban Missile Crisis. I don't think the US military and CIA are in crisis mode yet. While, yes the two situations are very different, I just wanted to demonstrate that it's not crisis mode. Plus, taking from the Cuban missile crisis experience, there would probably be lots of secret negotiations that go on when a crisis does occur. I think it's very easy to avoid war when neither party can see reasonable gain. Compare this to the experience of the two World Wars, in which case the parties involved felt, when they entered it, that the wars would be winnable and come out as a net benefit.