You can fire an SLBM from the Pacific or the Sea of Japan without traversing Russia or China.

NK's geographic position is interesting. Unless US boat is launching east from PRC's Yellow / Bohai sea / PLAN bastion, there isn't a trajectory to NK that doesn't look like it's heading towards PRC mainland. And even then, unless timed during summer months, prevailing winds is going to push fallout / radiation towards BJ. During winter downwind will drift to SKR / JP / east coast PRC. I don't know what proportional counter retaliation is, maybe a few nukes off CONUS west coast urban centres, but PRC isn't going to sit there and eat incidental radiation over major population centres even if target is NK.

Assuming you're striking first, yes. Nuclear subs take ~15 minutes to deploy, though, and that isn't the first option when counter striking. The U.S. president has six minutes to decide/launch a counter attack from the missile silos.

Annie Jacobsen has a book "Nuclear War: A Scenario" on all this where she interviews high ranking officials and pries into government documents related to nuclear war.

Isn't Jacobsen a bit of a crank? Some of her other books include ESP And Area 51.

I'm pretty sure she isn't. I take it as more of a research effort into highly classified areas of the government. She doesn't really push a narrative IMO.

On the other hand, NK is not launching a first strike that can take out all US land-bases ICBM sites anytime soon.

Against North Korea why would the US even use an ICBM? Why not a B-2 flown from Guam or from the continental US?

Are you saying that just because the great circle from US to NK goes over Russia? Can we not fire on a less optimal trajectory? Or from a submarine?

Wouldn’t it be more reasonable to Russia that the US is attacking NK and not just nuking Kamchatka?

Can the trajectory of an ICBM be inferred by the height of it’s arc?

> Wouldn’t it be more reasonable to Russia that the US is attacking NK and not just nuking Kamchatka?

I guess that depends on current relations between the two countries and assumes there wouldn't be a breakdown of communications when launches are detected.

> Can the trajectory of an ICBM be inferred by the height of it’s arc?

From the book I mentioned in another comment, Russia has very flawed satellite systems for tracking nuclear launches. There is a lot of focus on the fact that you don't have much time in the event of an imminent nuclear strike so I don't think there is much calculations being done if the missile is (generally) coming towards your homeland.

Thanks, that’s helpful, I’ll checkout that book