You can't blame Russia for imperialism, as they have no natural borders in the west, so expansion is the only way for them to maintain their state. It's just very basic geopolitics. Actually, the same applies to Ukraine.
So, where do they stop? At the Niemen? At the Oder-Neisse line? It's one vast plain until you get to North Sea. . .
The question begged here is who is Russia's enemy? Neither Ukraine nor Belarus have the military power nor the inclination to invade the Rodina. So is it the Poles? How about the Germans or the Danes?
The simple truth is Western Europe is utterly debellicized. The entire EU spends an average of just 2% of its GDP on military forces, and lacks the manpower, the equipment, and the willpower to project power beyond its own borders. Simply putting 50,000 men into Afghanistan has the NATO alliance at full stretch--and the Russians know this full well.
Western Europe has some 1.6 million men in uniform. Of these, only about 120,000 can be considered combat ready, and of those, only some 60,000 in all are "deployable". Russia has nothing to fear from its European neighbors.
Those who want to read more, go to my article Coalition of the Incapable
] . Though I wrote it almost three years ago, nothing much has changed. If anything, the situation has gotten worse due to the European financial crisis and subsequent recession,