It doesn't, in terms of who starts the war. My point is that realistically, there will be no attempt to invade Russia. If - say - Russia were to attempt an invassion of the Baltic states, NATO might react and even temporarily take some Russian territory, but it's not realistic that they'd attempt to keep it for long, let alone to invade Russia. One of the reasons is that they know Putin would very probably go nuclear if he can't win otherwise.
LordKiran said:
Even then, all the US need do is wait for another provocative military action from the Russian Government on the scale of the Ukraine invasion as a pretext for an ultimatum. "Get out or else."
Yes, but that's only enough for war. It's not enough for invassion.
LordKiran said:
As for the question of battlefield nukes, it really depends on where those nukes hit. If they're within US gains then that's really just another form of losing isn't it? Kill a few ten thousand men and poison your own lands for generations to come?
1. The extent of the effects of radiation from nukes over time and over large areas has been wildly exaggerated. Hiroshima and Nagasaki were hit by nukes much bigger than tactical ones. They're still large cities, with quality of life much better than most cities in the world (clearly, since they're in Japan).
2. Even if you were right about the poisoning, Putin would still do it since he cares a lot more about his own survival and the survival of his regime (closely linked) than he cares about keeping some areas in Russia clean from radiation.
LordKiran said:
If they're dropped within allied territories then Putin is just digging his own grave at that point and will only ensure a less secure position in peace talks at best.
Nukes might be used against military bases in Western Europe, Ukraine, etc., since small groups of special forces probably can get close enough by various infiltration means (e.g., submarines, small boats), and carry small tactical nukes. I'm not sure whether Putin would use them in that way at first when he decides to go nuclear, or at first only in Russian territory, and then escalate a bit more if - unlikely - the use of tactical nukes fails to deter an American invasion.
In any case, I don't think Putin would be digging his grave. On the contrary, if Russia is in fact being invaded by US forces, it would be in his interest to use tactical nukes, as that would increase his chances of survival in the long run, rather than decrease them. I don't think the invasion would be successful by the way, and precisely for that reason (tactical nukes).
Additionally, I'm pretty sure Putin would throw everything he has at American and other NATO satellites. If he only has ballistic missiles with big nukes for that (I don't know), then so be it. Satellites in many cases are quite easy to spot, have predictable orbits, and no defenses. Losing their satellites is a serious problem for NATO forces. But I think tactical nukes are probably much more decisive.