Say Putin after fake elections annexes Donetsk, Luhansk, Kherson and Zaporizhia and integrates them into Russia as has been widely speculated. Any attack would be an attack on Russia itself, thus enabling a full war standing to be declared, therefore in their mind validating the use of any means of defence.
He is not interested in any international recognition of such a land grab, all that matters is his own population. Control of the state is approaching that of the paranoic powers of the Stalinist regime in its worst days, it will only get worse.
There are a number of possibilities.
1~ His threats of using nuclear weapons “works” and the West restrain Ukraine from further attacks on their own land to prevent global war erupting. The result will be in a couple of years [or less] we will be back to where we are today.
2~Putin creates a false flag attack, let’s say in Crimea, he then carries out his threat and wipes Kiev off the map. Is he nuts enough? Would the “west retaliate”, would China and India come off the fence? Does Putin love Russia or himself more? My feelings there would be no military action but a possible global boycott, Russia might fail, but Putin would still be there forcing his own people to suffer direly,
3~ There is a populist revolution in Russia and Putin is overthrown. The lesson to those who want an authoritarian state is that the dictator will always sacrifice others for his own power, the return of full Stalinism/Putinism will create rivers of blood. Which would fail first, the state or the dictator? There are plenty of powerful cronies that have also bet their lot on Putin and if in power themselves might even be worse.
4~ Putin is a sane and rational being and thinks going nuclear is a step too far. I have seen no evidence lately of this. The war of attrition would go on and on.
5~ Those countries allowing Russia to stay in the game see the danger and impose full sanctions, thereby reducing the nuclear risk, as I don’t think Putin is crazy enough to take on the whole world [yet].
We are dealing with a frightened dictator and to those wanting this type of government take heed the future is far from certain. Strong dictatorial leaders, I can live without them as history shows the endgame is horrific.
My feeling is that Putin will bank on the west’s rationality/sanity winning the day, therefore I am sacrificing vegetables to the Great Goddess of Aneurysms this evening.