In UN there are LAWS about military WARS. All countries around the world have signed to obey this LAWS.
I do not want to go in details. I will just say that ANY use of low or lowest, tiny, mini etc. yield NUKE and NO MATTER HOW SMALL it is Mean All UN LAWS are broken....Resulting you country become PRIMARY Target for all countries around world. Any action used to This country is ALLOWED and WANTED to be used to Destroy the Threat for Human kind....
Sure, I know that. But I think Russia is way past considering UN and international laws an obstacle to obtaining their goals.
From a wargames perspective, the consequences to russia for using a nuke in Ukraine must be so devastating that they far outweigh the tactical gains. There is also an added modifier of how irrational the russian leadership has become, likely affecting internal decision making by shifting the cost-benefit calculus somewhat.
Russia is already turning into a pariah state, much like North Korea, but with the difference that Russia actually has a huge stockpile of nuclear arms (some of which are propably still operational), ballistic subs (ditto) and ICBMs (ditto). Mutually assured destruction relies on two rational parties, but i don't consider russia to be a rational actor right now.
Now, if we entertain the thought that russia would explode a nuclear device in Ukraine, it would not be a direct attack on a NATO-country or a NATO-ally. A counterstrike from the US would then have to be a exponential escalation into the 100 KT-range and into strategic rather than tactical nuclear war. At that point we are past an escalation chess-game and full on smashing the board.
Now, Russian doctrine uses a quite horrible tactic called "escalate to deescalate" where you raise the stakes to a point where the other side has to fold, thus getting you what you want. Brinksmanship galore, but codified.
<EDIT> There is some debate if the escalate-to-deescalate option includes nuclear weapons, in some of the articles i read from '17-18 it is argued that the threshold is higher rather than lower because russia now has "credible conventional methods and tools because of their modernised army". Well, that assumption is clearly out the window. Their other tools include economical pressure, exactly what we are seeing right now with the cutoff of gas, but that measure doesn't seem to go as planned either.
I can imagine a scenario where Putin, provided another few months of losses and sanctions would consider an escalation like that becoming more and more viable. The guy is 70 years old, he has 10 years left in power tops, he needs a proper "win" to be remembered as the "Great Vladimir", question is how far he is willing to go and how much he is willing to sacrifice to get that.
Also, suppose the Ukrainians manage to push Russia out, maybe even take back Crimea. What then? Would they invade Russian soil? And if they do, is that the red line? Then its about "defending the state".
I really want to see russia defeated, like utterly defeated, but it should be clear that it carries quite a bit of risk.
I really hope none of this is true, or at least highly unlikely. But I do not think this scenario is an impossibility anymore.
