Earlier quoted context omitted.
>They can never be invaded or conquered again, by anyone, ever. Why does thinking about nuclear weapons cause most people to think in absolutist terms like this? Maybe Russia was counting on getting a 15-minute warning of ICBMs approaching, but if a hostile military can station missile right on their southwestern border (523 miles from the center of Moscow) their plan goes out the window.
It wouldn't, because their SSBNs and their hidden silos would ensure the counter strike afterwards. USA isn't counting on a 15 minute warning either, MAD is ensured via second strike capability AFTER the first strike, if you are counting for the first strike you've already lost.
See: the Cuban Missile Crisis:
https://en.wikipedia.org/wiki/Cuban_Missile_Crisis
In any case, even in a MAD setting every side will be constantly trying to manoeuver to a position of advantage. That's what military people do when they're not actually fighting, kind of how computer nerds play video games when they're not coding, eh?