Byzantium was not Roman
Byzantium was not Roman
Most people are aware of Roman Empire. Fewer know about Byzantine Empire although it lasted much longer, more than a thousand years. It is also referred as Byzantium which was the capital, a shortened name. Constantine the Great renamed it to Constantinopolis or Constantinople (today's Instanbul) which means city (polis in Greek) of Constantine. There is a misconception that Byzantium was Roman.
Byzantium started as Eastern Roman Empire but certainly wasn't Roman. If it wasn't Roman, was it Greek (Hellenic)? It was Greek to a large degree but not entirely. The wars between Romans and Greeks (Hellenes) started in 215 BC. The battle of Pydna, in 168 BC, determined the conquest of Macedonia and the battle of Lefkopetra, in 146 BC, the conquest of the rest of Greece.
The beginning of Roman Empire is considered 31 BC, when Octavian was emperor. Its division into Greek (Hellenic) Eastern and Latin Western began under Diocletian in 286 AD and was finalized in 395 AD. The beginning of the Byzantine Empire is considered to be either 330 AD or 395 AD. In 330 AD, Constantine moved the capital of the briefly unified Roman Empire to Constantinople.
During this time, Rome was under Constantinople. After the division, Byzantine Empire and Western Roman Empire were separate and not connected. Rome was the capital of Western Roman Empire and Constaninople the capital of Byzantine Empire. The inhabitants of Byzantium were, in the first two centuries, Greek (Hellenic) or related tribes.
Greeks (Hellenes), Illyrians and Thracians were related. They lived for centuries before Roman conquest in a large area that contains today's Balkans and Turkey. They had settled northern of Balkans as well. The emperors of Byzantium came from the various regions of the Empire and were of Greek, Thracian or Illyrian origin. Constantine's father was Illyrian and his mother Helen was Greek.
Indicatively, places of origin of some emperors were; Moesia, Pannonia, Constantinople, Thrace, Dacia, Isauria, Cappadocia, Phrygia, Paphlagonia, Bithynia. Moesia was in northern Balkans and extended to today's Serbia, North Macedonia, Albania, Bulgaria, Romania, Moldavia, Ukraine. Pannonia was next to Moesia and included Hungary, Croatia, Slovenia, Bosnia, Serbia, Austria, Slovakia.
Moesia was inhabited by Thracians, Dacians and Illyrians. Pannonia was originally inhabited by Illyrians who mixed with Thracians and Dacians. Dacians who lived in Dacia were a Thracian tribe, like the Getae. Some believe that Thracians were a Greek tribe. Even if this was not the case, Thracians and Illyrians were related tribes to Greek tribes.
In other words, Greek and related tribes (Thracians and Illyrians), started from Cyprus, Crete, Asia Minor and reached Slovakia, Ukraine and even Poland and Czech Republic. Because Byzantium was a unified state, population movement within was easier and Greeks, Thracians and Illyrians mixed more. In addition to being related tribes, they mixed when they dwellt in the same Empire, the Byzantine Empire.
During Roman occupation, Romans sent troops but did not migrate. So the mix with Romans was small. On the contrary, the peaceful migration of Slavs to Byzantium, was massive and began in the 6th century AD. The first populations, Greek and related tribes, began to mix initially with Slavs. In the 7th century AD Bulgarians settled. The first ones were of Turkish origin but were later Slavified.
The language of Byzantium was Greek and the culture Hellenistic. The religion was Orthodox Christianity. The inhabitants and the administration, in the first centuries, were Greek and related tribes. In the later centuries, they mixed with Slavs. While we cannot say that Byzantium was purely Greek, it was quite Greek. In the second half of its duration, it was Greco-Slavic, including in term Greco related tribes (Thracians and Illyrians).
For many centuries it was the most economically and technologically developed region of the planet and was also militarily powerful. Byzantium had developed very close commercial, political, religious, cultural relations with Kievan Rus. Today's Belarusians, Russians and Ukrainians come from them. In western Ukraine are mostly of Polish descent.
The numbers of Slavs, relatively to the original populations, Greeks and related tribes, were significant. That is why today, in countries like Serbia and Bulgaria, we find nearly 50% Slavic percentage. In Croatia it is even higher. In Greece it is 25% while in Turkey it is lower. In the rest of the Balkan countries as well as in Hungary and Austria, it is between 25% and 50%.
Seljuk Turks appeared on the eastern borders around the 9th century AD. The Ottoman Turks followed. They eventually conquered Byzantium. Unlike the Romans who only sent troops, Turks migrated from the Altai region where they had lived for centuries. Thus there was some mixing of the previous populations (Greek, related tribes, Slavs), with Turks.
On the fringes of Byzantium came Hungarians and Avars who originated from Ural-Altai region. So in today's region that starts from Cyprus, Crete and Turkey in the South and reaches as far North as Hungary, Moldova, Slovakia and even further north, there is a similar racial mixture. They are Greek and related tribes (Thracians and Illyrians), mixed with Slavic mostly and Ural-Altaic (first Bulgarians, Turks, Hungarians, Avars) tribes to a lesser extent.