They'll try to rebuild a stronger military. Yes they have economic weakness, but they can get help from other countries that are benefited by a stronger Russia. They will try to take back former Soviet and Warsaw Pact states through direct and indirect means because, as Brett said, they are paranoid.
Western-style liberal democracies from their perspective are dangerous, both because of either being friendly to NATO or becoming part of NATO, but also because such nations can be prone to a populist uprising in which a Hitler takes control. To feel secure, such nations must be under direct or indirect control from Moscow, which means a dictatorship in charge, and the Russians would like a lot of them between themselves and NATO.
I don't believe they can defend it from Russia long-term, not easily anyway. Right now, yes, but longer-term, I have doubts. Also, it isn't per se "Russia" they'd be countering, but more a combined Russia-Chinese-North Korean-Iranian axis, in which Russia would be the muscle for that part of the world, as those countries know they have to stick together.
And yeah, I don't trust the likes of the France, Germany, Spain, Italy, etc...to be willing to go to war over say Latvia or Estonia being attacked.