If the USA nuked themselves to blame Russia, how would we know? Not like we would ever stage an attack on our own soil. That certainly never happened and as the recent pandemic showed, the Gov’t is deeply concerned about our health… They did produce the miracle vaccine after all.
Does Israel have nuclear subs? It just takes 1. Not that our greatest ally would ever attack us to pull us into war - that certainly has never ever happened.
So (((hypothetically))) how would we know?
Sending troops would have to be urgent. They're fully sealing the border shortly. No Western government will sign off on a hot war with a nuclear power. They might send as they have merc's already operating. But these aren't flying a flag except in support. Denied and disavowed. And munitions and aid.
It could escalate into a hot war the worse it gets. But immediately no support for boots on the ground flying another flag. Hence topically a jolt to it. But it doesn't need it. As propaganda reactors flare it causes more support. Sure if Nato gets hit, undeniable retaliation which could get very hot.
In answer to his question directly no. But never, is not an assumption. Let's suggest any conflict rides out for longer. What is the state of the Global economies this is impacting. Citizens start to cause unrest. What then happens if proxy's start to flare up.
Historically invasions have been cut short by funding, peaking unrest running off, the duration of conflict and the resistance to an occupation. Hence textbook; bog down arms funding patriotism, harass, sanction, propagate. It might divert their advance. But this is Russia an otherwise superpower. It has many of its own means, and when determined what's that textbook?