Assuming a single warhead and something small like NK's ICBMs which is in the 20-30kt range, yes. Now when you're dealing with modern ICBMs, like the ones the US, Russia, China and a few other countries have, the prognosis isn't as good. Modern ICBMs are MIRVs (multiple independently targetable reentry vehicle). For example the current Russian MIRV ICBM is the R-36M2 (NATO designation SS-18 Satan Mod 5) which carries 10 warheads each with a charge of 550-750kt. So on Nukemap punch in a single air-burst warhead in the 550-750kt range and imagine 10 of them spread over a wide area. That's what a single R-36M2 could do. Russia currently has 104 of them deployed. They also have 278 of the older R-36MUTTKh (NATO SS-18 Satan Mod 4) deployed which each carry 10 550kt warheads. Russia is in the process of deploying the successor to the R-36M, the RS-28 Sarmat (NATO designation SS-X-30 SATAN 2) which can carry a single warhead with a 50Mt charge or between 10-15 MIRV warheads or 24 hypersonic glide vehicles, depending on the configuration. A single RS-28 Sarmat in a MIRV or hypersonic glide vehicle configuration could flatten an area about the size of Texas. And if all that isn't horrific enough, it's hypersonic, which means all current missile defenses are useless against it.
I did the calculation for Ohio-class capabilities assuming it was only loaded with the smaller 100kT warheads (W76), as the 450kT ones (W88) are relatively rare, according to Nukemap's estimates for a 840m airburst a single sub can cover 1500sq km (~1/3rd of RH, 10x DC) in 20psi (severe damage or complete destruction of concrete buildings, ~100% fatality), 1800 in 1000 rem (~95% protracted mortality) and 7700 sq km (Delaware, half of Connecticut) in 5 psi (~universal collapse of residential buildings, widespread fatalities).
But at the same time, we're moving past deterrence. The USSR fell 26 years ago. There's "deterrence" and there's "we can wipe out the entire planet". It's especially disconcerting when you consider that in most nuclear armed countries, US included, the authority to launch a nuclear strike lies solely with one person.
We are in no way moving past deterrence. SALT, START, ABMT, etc essentially codified it.
And deterrence is predicated upon creating the absolute certainty in your enemy's mind that you will leave their country a smoking, radioactive hellscape if they attack you.
This requires convincing them that the decision will be made, were it to come to that. Not "Oh, but a mid level officer might ignore the command."
In nuclear game theory, the less certain your opponent is of your resolve and capability, the more likely nuclear armageddon is.
I'd imagine it makes it less stable simply from a complexity = narrower bounds of stability standpoint, but fundamentally it doesn't change anything.
That's why nuclear fingerprinting and global monitoring have been so heavily invested in. "Safety in numbers" isn't a defense if the retaliatory strike still hits all the belligerents.
You vastly overestimated the dammage from a MIRV. Nukes are sub liner as a higher percentage of the energy ends up in the upper atmosphere as you increase yield. Nagasaki's Was 20kt and had favorable geographic conditions along with wooden buildings and a large number of people from the same city survived. 500kt still have left survivors in the same city though few.
So, yes a MIV could take out 8-10 cities across Texas while not impacting 99% of the land. But, a more likely approach is to carpet bomb suberbs and redundantly target cities with different warheads from different ICBMs.
Thus, 1000 MIRVs would not get 1000x the dammage as single areas would be targeted multiple times and of course targets get harder to pick. Central West Virginia for example due to all those mountains and minimal population would take a lot of nukes or largely get left alone.
> So, yes a MIV could take out 8-10 cities across Texas while not impacting 99% of the land. But, a more likely approach is to carpet bomb suburbs and redundantly target cities with different warheads from different ICBMs.
Why? Wouldn't it be more useful from a militaristic perspective to take out enemy missile silos, industrial plants which could be converted to produce wartime materials, and to take out military bases? Essentially, target cities, ignore the residential areas except for ones that are near a missile silo? What strategic advantage could possibly come from carpet bombing suburbs?
The world only has on the order of a thousand of these things. Russia, as the GP points out, only has ~300. They can't just glass the opposing hemisphere, they have to pick and choose important targets.
Total war, if you reduce the US population from 300 million to 10 million we are a vastly smaller threat mid term. Consider, if you removed everything but 1,000,000 infantry they would need to go make food, bullets, boats etc. On the other hand if you have 100 million civilians they can quickly train a few % how to shoot and will be very angry while producing a surplus to keep a war going.
The general assumption is an ICBMs counter attack happens when your attack is in the air. So, you would mostly be hitting empty silos thus your country has little military or economic strength left. Worse, it's much cheaper to fake some silos in the middle of nowhere than a suburb. 'Wasting' nukes on corn fields is very costly.
How has a 500kt warhead left survivors in a city? No warheads or bombs that large have ever been deployed in an actual conflict and so have never been used on a city.
The 100% kills zone is surrounded by a much larger 99-95% kill zone. Militarily 98% = total destruction, but when you start talking about 100,000 people you need several 9's.
http://nationalinterest.org/blog/the-buzz/russias-new-rs-28-...
https://en.wikipedia.org/wiki/R-36M
https://en.wikipedia.org/wiki/RS-28_Sarmat