geonuc wrote:How do you justify a nuclear strike? Necessity. If North Korea is causing grave damage or is in position to overrun South Korea, you use what weaponry you must. Of course, there are political as well as strategic military considerations to using nuclear weapons instead of conventional. Mind you, I don't advocate using nuclear weapons. I'm just saying it could be justified under certain circumstances.
I don't think North Korea has any air defenses that could shoot down a significant number of Tomahawks, if any. Even Russia would have a hard time with Tomahawks. They are low-flying and have very small radar cross-secions. The US has other varieties of cruise missile, as well.
I don't think North Korea has a nuclear torpedo or is remotely close to having one. Not sure how they would tow a nuclear weapon close to a carrier, much less set it off.
Perhaps it depends on what you mean by "justify", do you mean satisfying your own cognitive dissonance or that of the general US public, satisfying present US law, satisfying international law, satisfying the qualms that might be held by allies, satisfying the qualms of un-involved countries, or satisfying the qualms of adversaries who might perceive it as an escalation and
casus belli? Based on the Nautilus report (and others by them), the use of nuclear weapons is not warranted because conventional counterforce capabilities are presumed to be at least as adequate, sometimes better, and have fewer risks of escalation. Precision munitions delivery is claimed to have gotten even better since that study (2011) and the previous study they based some of their tactical analysis on (from the 1970s, IIRC).
My understanding is NATO planned to use nukes in Europe to counter Warsaw Pact armored concentrations. However, that is a tactical use. There might be a similar scenario on the Korean Peninsula if the DPRK were to invade. However, an artillery barrage is unlikely to be stopped by a nuclear attack. The hardened artillery positions are relatively protected, both individually and by general mountainous terrain, meaning a nuclear response necessary to stop the shelling would require tens to hundreds of nuclear explosions. Meanwhile, the fallout might kill more south Koreans than enemy artillery fire. A strategic use well beyond the DMZ, attempting to kill DPRK leadership might work with fewer strikes, but it might kill a lot of north Korean civilians and be seen as an escalation to counter-value nuclear warfare.
I don't know how easy or hard it is to shoot down a Tomahawk. One was apparently shot down in the Balkan conflicts. There are claims that dozens were shot down in Syria recently, though I have no idea if that's true or not. North Korea is assumed to have good, if not cutting edge, air defenses. I don't think we've used any against Russia, so that might just be speculation. I'm not making an assumption, I'm legitimately curious.
As for a nuclear attack on the carrier, it would depend on doctrine. If they are blasting away on active sonar to look for a mine or sub, it might be harder to attack, although it might be easier to locate and track them for an attempt. If the carrier task force relies on passive sonar, then a quiet sub or mine might go undetected until too late. Also factoring in is how many airborne ASW assets they use and where. The Sea of Japan is fairly deep, so bottom mines might not work and subs wouldn't be able to bottom out.
However, military history suggests that forces can be manipulated into deploying in a manner that allows a secretive attack to work. If a DPRK sub goes active in one location, or they launch a bomber sortie or a ballistic missile toward the carrier group, it might maneuver in a way that could be anticipated (e.g. turning into the wind). Or they might attack in the straits between Japan and the mainland when the carrier task force is passing through the constriction. Or maybe they could attack it during a port visit.