So, to start off, if you’d ask a Byzantine from the year 1000 your question, he’d probably scratch his head and ask you what the hell the ‘Byzantine Empire’ is. The Byzantines kept calling themselves and their empire Roman until late Medieval times. To them, the distinction we make between Byzantium and the Roman Empire, would probably seem quite odd and maybe even disrespectful – they saw their state as standing in direct succession to and continuity of the Rome of Caesar and Augustus. The name ‘Byzantine Empire’ itself is a later construct by Western European historians, as is the historiographical split between a Roman and a Byzantine Empire.

Now we’ve got that definition thingy out of way, we need to address something else. Because the distinction between Eastern Roman and Byzantine is a historical construct, there’s been much discussion of where the one end and the other starts. As a different example, let’s look at the distinction between the Middle Ages and the Early Modern Period. When we don’t get too specific, it seems to be a pretty straightforward and reasonable categorisation of two different periods. But when we zoom in, things get problematic. What is the date or year where one ends and the other begins? The fall of Constantinople in 1453? The discovery of the Americas 1492? The kick-off of the protestant reformation in 1517? If so, why that specific event and not the others?

The crisis of the 7th century

Anyhow, I think it’s say to safe that the 7th Century (-/+ 630 – 670) is considered to be the divide between ERE and Byzantine by most. The 7th century was a century of great tribulation for the Byzantine/Eastern Roman Empire. Where around 600, it was a huge, wealthy and powerful multi-ethnic empire, reaching from the Atlantic to Mesopotamia and from the Alps to Sudan, at the end of the century it had lost about three-quarters of its territory to invaders. This steep decline of the Byzantine/ERE Empire has a lot a to do with the sudden and meteoric rise of Islam and the first Caliphate. The Arabs overran Byzantine Egypt, Africa and Syria with ease, exhausted as the Byzantine military was at that point by continuous warfare with their Sassanid Persian neighbours. It wasn’t just Arabs though – Slavs and Avars were descending on the Balkans, Lombards on the Italian peninsula and the Visigoths were always pressuring the emperor’s Iberian possessions . It’s a small miracle that the ERE/Byzantine Empire even survived this period as a state to begin with.

Let me illustrate this with two maps. Here is a map of the Empire in 600, here is a map of the Empire a little over a century later. By 717, the empire had been mostly reduced to territories where ethnic Greeks were in the majority, in contrast to the map of the situation to 600, where the Empire encompassed a multitude of different peoples and cultures. The international scene is completely overhauled as well. In the year 600, the Eastern Roman Empire had to fear none but the Persians, with whom they warred on-and-off. But by 700 the Persian Sassanid Empire had collapsed and the enfeebled Byzantine Empire was dwarfed by the powerful Umayyad caliphate which had taken Byzantium’s richest and most populated lands and raided the remaining at will. The scene was set for a new era: the fight against ever advancing Islamic forces would dominate the Empire’s politics for the next 700 years.

So to recite the above; there’s three reasons why we can locate the split in the middle of the 7th century. The first is that the Empire went from a far-spanning, multi-ethnic empire to a much smaller, predominantly ethnically Greek empire. ‘Roman’ provinces like Iberia, Egypt and Africa were lost to the Empire for good and Anatolia and Greece were now the core of the Empire. The second reason is that the rise of Islam in the 7th century set the stage for the endless political and military conflict between the Byzantines and Muslim invaders, first the Arabs, later the Turks. Together, these factors make the Constantinople of 700 a completely different place from Constantinople in 600.

Roman or Greek?

So this is a little trickier. When can we ‘correctly’ speak of a Greek in contrary to a Roman empire? It kind of depends on your interpretation of this question. Culturally speaking, pretty much the entire eastern half of the Roman Empire had been under strong Hellenistic/Greek influence since the conquests of Alexander. The cities and cultures in Egypt, Greece and Babylonia were much older and (if I may) much more refined and culturally accomplished than Rome was by the time it subjugated them. Greek stayed the lingua franca of the eastern half of the Roman Empire and culturally speaking, it was Greece that conquered Rome, not the other way around. Latin was mostly used ceremonially and administratively. Seeing it from this perspective, the Eastern Roman Empire had never really been culturally or linguistically Latin or Roman at all.

If we want to take a more ethnical perspective on Romans and Greeks than I would point to, as you’ve probably guessed by now, the middle of the 7th century as the breaking point. While the ERE definitely wasn’t ethnically Roman/Italian for more than a negligible share, it was very ‘Roman Empire’ in the sense that it spanned a multitude of tribes, cultures and ethnicities. With the loss of the Iberian, North-African and Syrian provinces to the Rashidun and Umayyad armies, Greek culture became even more dominant in Byzantium then before. There were still many different kinds tribes and cultures in the Byzantine Empire, but the Empire was far more centred on Greece and (Western) Anatolia then it had been before and Greeks were in the majority– even if they kept on referring to themselves as Roman.

The moral of the story is that historical monikers and categories are an important tool in the historical science, which are practical when talking about centuries-long eras, but sometimes messy and ill-defined when closely scrutinized. Nobody woke up in Constantinople on the 1st of January 650 with the realisation that they were now living in the Greek Byzantine Empire in contrast to the Eastern Roman Empire they were living in yesterday. Categorizations are always invented and applied by others, long after the time period itself. They usually reflect hindsight and not the feelings or ideas of the long-dead people they describe. Whatever their virtues or vices, at least they make great stuff for historians to bicker over.