Poland is mostly Polish, there are not many other ethnic groups there. This does beg a larger question though, any bordering nation that is watching this and not rethinking their defense/reserve strategy are idiots. I’ve always thought that Swiss have a terrific solution to this; prepare defenses throughout the country and assure the populace is trained. Based on the Swiss Model, the Poles could easily mobilize a five or six million man army.
Poland is mobilizing, they’ve also decided to ramp up fracking to try to reduce dependence on Russian Natural Gas.
One of the ramifications of the recent events in Ukraine, is that Poland is going to emerge as a big player in Europe, perhaps even forming a new alliance with the other Central European and Baltic Countries.