Interesting. But I doubt South Korea would attack the North, knowing perfectly well their main cities can be razed to the ground by NK's conventional, not even nuclear weapons. At the same time, I don't think North Korea would start blasting off nukes over major cities, that would be pointless. In the worst case, a single nuke over the ocean, but close enough to a target, would be a sufficient signal of readiness to defend itself. Directing nuclear bombs to major targets as a first move doesn't make much sense, you don't leave the enemy any other option than obliterating you.

Note that the incident is started by North Korea downing a civilian jet, even if by mistake, South Korea reacting, NK going berserk with nukes, US responding with conventional weapons... Hmmm, a bit kind towards the West. The US certainly come out as the level headed guys, which doesn't sound very coherent with recent rhetoric and events.

In the book, the guy with the "Nuclear football" basically runs away at one point, but yeah, I'm not seeing a non-nuclear response. Tit-for-tat is the entire basis of MAD.

The conventional response is modeled on Mattis' philosophy. The US clearly comes out divided as a country and destroyed politically and economically because Trump couldn't tweet.