Although the peak of the byzantine empire was through the Macedonian dynasty's era, Justinian's era has some very interesting incidentes and is pleasant like Ancient Rome or Ancient Greek history.The truth is that after Sassanid empire lots of "evil" foes surrounded the empire and the fihgt of its existance started. So ,after Heraclius, Byzantine history becomes more specific you know, because of the territorial shrink (loss of Northern Africa and N.Italy and S.Spain) we now talk about Grecko_Roman Empire , not the continuation of the "Global"Roman Empire.I think that this is the reason that not many westerners are interested to learn about Byzantine Empire,nor Greeks but this is for other reasons
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I don't think that Bulgaro-Byzantine conflicts affected that much the western civilization nor the wars with turks, arabs and normans.There wasn't any speciefic battle (except the 2victories against Arabs in 8th century)that is noteable from westerners.
Eventhough Byzantium was the main frontier of christianity and Europe....