Europe can be divided along many differing historical lines, normally corresponding to those parts that were inside or outside a particular cultural phenomenon, empire or political division. The areas varied at different times, and so it is arguable as to which were part of some common historical entity (e.g., were Germany or Britain part of Roman Europe as they were only partly and relatively briefly part of the Empire—or were the countries of the former communist Yugoslavia part of the Eastern Bloc, since it was not in the Warsaw Pact).