Sharing continuity with the classical Roman Empire gave the Byzantine empire a technological and artistic advantage over its neighbors, whom Byzantines considered barbarians.
In the years that followed, the prominence and influence of Constantinople continued to decline, and the rise of Islam challenged the Byzantine Empire's political dominance.
Additionally, lords and nobles saw their power fall after the Crusades, as Europeans came to know more advanced civilizations like the Byzantine Empire.
Historians believe this was the first time the bubonic plague reached European shores, and it was deadliest around Constantinople, the capital of the Byzantine Empire.
Byzantine missionaries created an alphabet for Slavic languages based on a modified Greek script while Rus Viking warriors served as the Byzantine Emperor's elite guard.
In Osman's time, the Anatolian peninsula was a patchwork of Turkic principalities sandwiched between a crumbling Byzantine Empire and weakened Sultanate of the Seljuk of Rum.
Farther east, the people of the so-called Byzantine Empire would deny that they had ever stopped being Romans, even though the Byzantines would tell you this not in Latin, but in ancient Greek.
To set the stage for the festivities, Mr Erdogan has given a makeover to the country's biggest city, the ancient home of the Ottomans (and the Byzantines before them).
While he was there, he learned more about Turkish history, and he used that knowledge a few years later to write another historical novel, this time about the Byzantine Empire.
The Byzantines had carried on Roman traditions for centuries but by 1000AD they were losing territory rapidly to the rising Ottoman Turkish Empire, but that was not their only problem.
When the Roman Empire was officially split into eastern and western halves in 395 AD, Constantinople became the capital of the Eastern Roman Empire, what historians now call the Byzantine Empire.