So what if the Byzantines invaded the Balkans earlier, conquering everything they did under Basil II. It could either be earlier (mid 900s) or the same time as Basil did (circa 1019)...
If the Byzantines manage to hold onto these areas for several centuries (say at least until the 1200s. Would they have been able to (through resettlements, linguistic stuff, etc, have been able to hellenize many or most of the Slavs in the conquered region? They did it with Greece after the Slavs invaded, so why not other areas.
Would that be possible at all? And if it is, how could it be accomplished?