I recommend looking up European military readiness levels before diving too deep into fantasies. Who is supposed to invade Russia? Latvia, with its tank army of exactly zero tanks? Or a major country like Germany, with its barely 100 operational tanks and enough artillery ammunition for just two days?

Even in Russia, only complete loonies treats this as a plausible scenario. That's why you can see bunkers and anti-tank ditches and defensive lines being built on the European side of the Russian border, and nothing of this sort on the Russian side. They don't even have a basic chain-link fence. Mushroomers sometimes get lost and just walk into Russia.