- May 2014
If Russia will expand into the Caucasus and the Byzantine Empire will maintain the borders that it had in 1025, then the Russians and Byzantines are going to have a common border.Kingdom of Poland and Grand Duchy of Lithuania had common border. Century or so before de jure establishment of the Commonwealth these two states had been unified through personal union aka marriage between the rulers of these two medieval states. Where is the common border between the Eastern Roman Empire aka Byzantium and Russia? During the time of Sviatoslav of Kiev they had one, but this had been before christianization of Rus and long before the establishment of Moscow grand duchy, tzardom and empire. How you gonna unite two entities that are situated on different parts of the continent with enormous distance between them, two states that had nothing in common but a religion?
What about if the Byzantine Empire would have kept the borders that it had in 1025?Perhaps--but as a Commonwealth (in the British sense, not the American). If the Byzantine Empire survived only as it was in 1453, Russia would be the dominant power.