How would the West respond if Russia uses a nuclear weapon in Ukraine?

[Antonio the Sixth]

Nuclear attack is the only reasonable response to Putin should that happen. The alternative is submitting to his rule now.

The goal would be to take out their missile bases/military capacities rather than Russian cities, save perhaps Moscow.

Even if it worked (and it almost certainly wouldn't), this would kill millions of civilians and therefore isn't reasonable.

If you allow Putin to use nuclear weapons with impunity then you have surrendered to his tyranny. Perhaps some would sooner live on their knees, but like the people of Ukraine I’d sooner die on my feet.

There are options between 'impunity' and nuclear mass murder which could dissuade future use of nuclear weapons. In the long run, mutually assured destruction would have an excellent chance of dissuading future use, but that's akin to cutting both of your legs off to remind yourself that playing with knives is bad.
 
The goal of any response to nuclear strikes would be to prevent more of them, in the long and the short term. If Putin nukes Ukraine, he will likely start with a warning shot - a tactical nuke on Snake Island or a lightly populated area. Commencing MAD in response to that would be a decision we'd take, not Ukraine - but there's a fair chance some of the Russian nukes fired in response would be aimed at Ukraine anyway. They wouldn't be warning shots.

Proportionality is the key. If Putin nukes Snake Island, then we need to destroy something of equal tactical, strategic and political value to him. If that can be done conventionally, then sure, I guess, go for it. But nukes can't be off the table at that point.

[TiltsAreUnderrated]

Nuclear attack is the only reasonable response to Putin should that happen. The alternative is submitting to his rule now.

The goal would be to take out their missile bases/military capacities rather than Russian cities, save perhaps Moscow.

Even if it worked (and it almost certainly wouldn't), this would kill millions of civilians and therefore isn't reasonable.

If you allow Putin to use nuclear weapons with impunity then you have surrendered to his tyranny. Perhaps some would sooner live on their knees, but like the people of Ukraine I’d sooner die on my feet.

There are options between 'impunity' and nuclear mass murder which could dissuade future use of nuclear weapons. In the long run, mutually assured destruction would have an excellent chance of dissuading future use, but that's akin to cutting both of your legs off to remind yourself that playing with knives is bad.
 
The goal of any response to nuclear strikes would be to prevent more of them, in the long and the short term. If Putin nukes Ukraine, he will likely start with a warning shot - a tactical nuke on Snake Island or a lightly populated area. Commencing MAD in response to that would be a decision we'd take, not Ukraine - but there's a fair chance some of the Russian nukes fired in response would be aimed at Ukraine anyway. They wouldn't be warning shots.

Proportionality is the key. If Putin nukes Snake Island, then we need to destroy something of equal tactical, strategic and political value to him. If that can be done conventionally, then sure, I guess, go for it. But nukes can't be off the table at that point.

Why not? Like most leaders, Putin cares more about himself and (parts of) his inner circle than his people. You don’t need to kill millions to threaten what he values most, so why engage in utterly needless destruction?

Assassination or kidnapping attempts might trigger a Russian nuclear response, but MAD is even more likely to do this - and if you’re ok with the risks and human costs of MAD, you should be ok with the risks and costs of these things. To be clear, I’m not saying they would be sensible measures, but I struggle to see how they’d make less sense than nuclear bombardment.

[Antonio the Sixth]

Nuclear attack is the only reasonable response to Putin should that happen. The alternative is submitting to his rule now.

The goal would be to take out their missile bases/military capacities rather than Russian cities, save perhaps Moscow.

Even if it worked (and it almost certainly wouldn't), this would kill millions of civilians and therefore isn't reasonable.

If you allow Putin to use nuclear weapons with impunity then you have surrendered to his tyranny. Perhaps some would sooner live on their knees, but like the people of Ukraine I’d sooner die on my feet.

There are options between 'impunity' and nuclear mass murder which could dissuade future use of nuclear weapons. In the long run, mutually assured destruction would have an excellent chance of dissuading future use, but that's akin to cutting both of your legs off to remind yourself that playing with knives is bad.
 
The goal of any response to nuclear strikes would be to prevent more of them, in the long and the short term. If Putin nukes Ukraine, he will likely start with a warning shot - a tactical nuke on Snake Island or a lightly populated area. Commencing MAD in response to that would be a decision we'd take, not Ukraine - but there's a fair chance some of the Russian nukes fired in response would be aimed at Ukraine anyway. They wouldn't be warning shots.

Proportionality is the key. If Putin nukes Snake Island, then we need to destroy something of equal tactical, strategic and political value to him. If that can be done conventionally, then sure, I guess, go for it. But nukes can't be off the table at that point.

Why not? Like most leaders, Putin cares more about himself and (parts of) his inner circle than his people. You don’t need to kill millions to threaten what he values most, so why engage in utterly needless destruction?

Assassination or kidnapping attempts might trigger a Russian nuclear response, but MAD is even more likely to do this - and if you’re ok with the risks and human costs of MAD, you should be ok with the risks and costs of these things. To be clear, I’m not saying they would be sensible measures, but I struggle to see how they’d make less sense than nuclear bombardment.

When nukes are involved, it's foolish to think only of the "here and now" of a particular situation. This is something that affects every country, everywhere. If Putin uses a nuke and only gets a slap on the wrist in response, even if you're absolutely confident that it would be enough to convince Putin specifically to back down from this specific confrontation, you have to think about all the other nuclear powers that are watching and taking notes. What if someone else looks at our response and goes "sure, I can take it"? Well now it's not just Russia you have to worry about.

The only way to ensure we don't end up with a global nuclear war is to make it very clear that the first country that breaks the nuclear taboo will be the one to suffer the most from it. Sure, what that means precisely might change from one country to the other, but it absolutely, critically, must be something so bad that everyone else in the world would consider it an unacceptable loss.

[Middle-aged Europe]

I think one possible side-effect has been neglected so far in this thread.

Following the invasion of Ukraine there had been some low-key discussion whether the EU should start building up a nuclear arsenal of its own (beyond the French one). Russia using a tactical nuke in Ukraine would make that all but certain, I guess, for reasons of deterrence.

[Splash]

I am thankful that I am not in a position to make that determination but I think it would depend on the yield of the nuclear device used as well as the target. If the Russians "just" used a tactical nuclear device with a low yield and minimal fallout on a purely military target then I think the West might respond by (1) increasing lethal aid to the Ukrainians, (2) strengthening sanctions and (3) attacking a series of DNR/LPR targets in occupied Ukraine as well as one or more medium-to-high value Russian military assets in Crimea or the Black Sea. 

Cyber attacks might also be on the table. In February, Biden was presented with a series of options that would have resulted in the degradation of Russia's power grid as well as chaos in their transportation network by stopping trains in their track. I believe such options were deliberately leaked at the time to show that Biden was taking a more "measured" approach and that the US had the capability to carry out these kind of attacks should Russia escalate.

https://www.nbcnews.com/politics/national-security/biden-presented-options-massive-cyberattacks-russia-rcna17558

[certified hummus supporter 🇵🇸🤝🇺🇸🤝🇺🇦]

Eradicate the very notion and concept of a "Russia" off the face of the Earth

[MABA 2020]

An impossible decision, you can't do nothing and allow such an action to go unpunished and yet nuclear war would be an unimaginable horror.

I honestly have no idea what the right answer is

[Statilius the Epicurean]

I imagine it would respond with a conventional NATO air campaign designed to destroy the Russian military in Ukraine and disable any further deployment of tactical nuclear weapons. NATO has dominance in a conventional conflict so a nuclear response would be unnecessary.

If despite a conventional NATO intervention Russia continued to use tactical nuclear weapons effectively or say escalated to NATO territory, then I think you may see a nuclear response in kind.

[Yoda]

We have to use nukes on Russia then, as awful as that would be. Can't really think of another scenario. If we don't use them after one Russian nuke, the threat is gone.

This is my line of thinking as well. Putin is a terrorist with nuclear weapons. What's the only thing worse than that? A terrorist with nukes who knows the West will not respond with nukes if he uses them first. Putin would literally be able to hold the world hostage if we were to show indecision in such a scenario.

[CumbrianLefty]

Not nuking back straight away and "showing indecision" by no means have to be the same thing.

[Yoda]

https://www.theatlantic.com/ideas/archive/2022/06/russia-ukraine-nuclear-weapon-us-response/661315/

This article is a good read into various ideas floating around the powers that be (schlosser also wrote a really good book on the history of nuclear weaponry). The general consensus seems to be that if russia was to launch a tactical nuke on a military target, the US would respond in conventional means, through for example targeting the russian navy - as well as using the moral high ground to get the fence sitting nations away from Moscow. Especially interesting bit about the Obama era training exercise on how to deal with a russian invasion of the baltics (Obama's top guys recommended a nuclear attack on Belarus, Biden's allies recommend purely conventional response).

You know what, I'm in the proportional response camp as I believe not doing so would be inviting Putin to view us as unwilling to use nukes in any scenario (which obviously would be a disaster that results in him becoming a completely unleashed nuclear-armed terrorist), but if Russia launched a tactical nuke I could see, for example, us taking out the Russian fleet in the Black Sea as a proportional response. That would be acceptable.

[Darthpi – Anti-Florida Activist]

An impossible decision, you can't do nothing and allow such an action to go unpunished and yet nuclear war would be an unimaginable horror.

I honestly have no idea what the right answer is

The additional problem here is that if you choose a conventional response after Russia has already used nuclear weapons in Ukraine, it would seem to me that there is significant reason to expect a Russian nuclear response against America and NATO. If they've already used them once against Ukraine, there probably isn't going to be much restraint in using them again against additonal targets.

The key is, obviously, to keep Putin from making that sort of catastrophic decision in the first place.

[CumbrianLefty]

An impossible decision, you can't do nothing and allow such an action to go unpunished and yet nuclear war would be an unimaginable horror.

I honestly have no idea what the right answer is

The additional problem here is that if you choose a conventional response after Russia has already used nuclear weapons in Ukraine, it would seem to me that there is significant reason to expect a Russian nuclear response against America and NATO. If they've already used them once against Ukraine, there probably isn't going to be much restraint in using them again against additonal targets.

The key is, obviously, to keep Putin from making that sort of catastrophic decision in the first place.

That doesn't follow at all, even Putin knows what response *that* would entail.

(very likely a nuclear strike to take him out personally, in the first instance)