Extremely developed thought experiment maybe. Only 2 nuclear weapons have ever been dropped. Which is why I say it's a massive assumption.

You tell me. How does this escalate into a total destruction scenario? Russia uses a small nuke on a military target in the middle of nowhere Ukraine. ___________________________. Everyone is firing nukes at eachother.

Fill in the blank.

We are not talking about the scenario where Russia fire a nuke at Washington, Colorado, CA, Montana, forward deployments, etc. and the US responds in kind while nukes are en-route.

Of course the flowchart that fill that blank has other outcomes than total nuclear war, but you aren't considering how unacceptable those outcomes are to those involved or the feedback loops involved.

Let me ask you this question. Why did Russia use a small nuke on a military target in the middle of nowhere Ukraine? Because the outcome was positive for Russia... but the only way that can be true is if the cost of using a small nuke was better than the alternatives. This either means it was a demonstration / political action or... 1 or more Russian units in the Ukraine are armed with tactical nukes and it was a militarily sound option so by definition you'll see more nuke flying around at least from the Russian side when it's militarily sound. Now due to the realities of logistics that means there is capturable nuclear material on the battlefield.

If it's a demonstration/political action what do you think it was meant to accomplish? Either the consequences will be less detrimental than the military gain and so Russia can use tactical nukes and will do so if it improves the military situation... or the consequences will be at a level detrimental to Russia.

See the premise of the question is flawed in that Russia doesn't just use one Nuke in the middle of nowhere, because everyone already knows Russia has nukes. Russia is trying to demonstrate it will use them and so the actions from that are either a Ukraine alliance capitulation, Russia can continue the war just the same but with whatever ever extra political consequences of using 1 nuke, or continue the situation using Nukes.

You see the issue right? Should the Ukraine alliance surrender to a single tactical nuke when it hasn't to the threat of strategic nukes? Russia can't fire that first Nuke without being a country willing to use tactical nukes on the battlefield and what did they gain if not the use of those nukes to ensure a military victory because it hasn't ensured a diplomatic one.

So the statement becomes: Russia uses tactical nukes across the battlefield. ____. Everyone is firing nukes at eachother.

That last sentence is synonymous with "Strategic nukes being fired by ICBM" which is incredibly likely when 1 non scheduled ICBM is fired. While you're right that 1 tactical nuke in the middle of nowhere wouldn't ensure MAD, it is not a massive assumption that the realities around that 1 nuke being used would.

> Russia uses a small nuke on a military target in the middle of nowhere Ukraine. ___________________________. Everyone is firing nukes at eachother.

While all-out international global war isn't guaranteed in this scenario, I don't see why you'd be so confident as to imply that it was very unlikely. For me, the biggest fear in terms of escalating to nuclear war is the time when some nuclear power is eventually beaten in conventional war to the point of utter desperation, and ends up going all out with nukes as a Hail Mary or a "if I can't have it, no one will" move.

Russia uses a strategic nuke in a military move in Ukraine. The rest of Europe, fearing a normalization of strategic nuke use and more widespread uses of these weapons (including outside Ukraine) begin deploying in Ukraine to help push back the Russian forces - especially since Russia showing the willingness to use nukes at all makes them and their military a lot more intimidating and urgently threatening to the rest of Europe than before. Russia perceives this deployment as a direct declaration of war from NATO and invades (one of) the Baltic states to create instability and drive the attention and manpower away from their primary front line. This leads to full war and mobilization in Europe. Russia is eventually pushed back to their original borders, but with what the situation became, Western countries are nervous that not dealing with this once and for all would just be giving Russia a timeout to regroup and re-invade with more nukes at a later point. They press on, and eventually Russia is put in a desperate situation, which leads to them using nukes more broadly against their enemies for one of the reasons I described at the start of this comment. Other nuclear states begin targeting known nuclear launch sites in Russia with strikes of their own, to cripple their launch ability. This is nuclear war.

I'm not saying this scenario is likely, but this is just one attempt at filling in the blank. If you can imagine a future - any future at all where Russia, or North Korea, or India, or Pakistan, or Israel have their existence threatened at any point in the future ever, this is when nuclear war becomes a serious possibility.

>How does this escalate into a total destruction scenario?

My favorite historical documentary: https://www.youtube.com/watch?v=Pk-kbjw0Y8U (my new favorite part is America realizing "fuck, we're dumasses" far too late into the warfare they started).

That is to say: you're assuming a lot of good faith in a time of unrest with several leaders looking for any excuse enact martial law. For all we know, the blank is "Trump overreacts and authorizes a nuclear strike on Los Angeles"(note the word "authorizes". Despite the media, the president cannot unilaterally fire a nuclear warhead). That bizarre threat alone might escalate completely unrelated events and boom. Chaos.

I think this perfectly demonstrates my point that the path from isolated tactical nuke to wide scale nuclear war is quite unclear and by no means necessary. Thank you.

I wish it was a clear path. That's the scariest part. Remember that one assassation escalated to The Great War.

It'll be a similar flimsy straw breaking that will mark the start of nuclear conflict after years of rising tensions. And by then pandora's box will be opened.