The Byzantine empire, once comprising most of the eastern portions of the Holy Roman empire, broke away (for a number of reasons) and became its own stand-alone civilization, even if it did draw on a lot of inspiration from other peoples. However, their ascension into history would not have been possible were it not for the many figures who managed to stand out among the centuries: prominent rulers and political figures, influential thinkers and iconic artists.
Constantine’s first great act came in AD 313 when he issued the Edict of Milan. This proclamation legalized Christian worship throughout the Roman empire, an act which would eventually phase out pagan rituals altogether. Even though his rule was established before the Byzantine empire (in fact, he ruled the western portion of the Roman empire before the eastern), Constantine played a significant role in reuniting the Roman empire (which was ruled by multiple emperors at the time) by defeating Licinius and establishing Christianity as the state religion through the Nicene Creed in AD 325. Constantine was also responsible for the founding of Constantinople, the city that would later serve as the capital of the entirety of the Byzantine empire as well as the center of the later-to-come Orthodox Church.
Undertaking a massive overhaul of construction projects during his 40-year rule, Justinian is likely best known for commissioning what would be the final iteration of the Hagia Sophia among a litany of other churches and structures adding to the fame of the Byzantine empire, as well as being a great patron for Byzantine cultural art in the form of mosaics. He was also responsible for historic military campaigns to reclaim lands previously lost to Germanic invaders, meeting with success as far as Italy and re-establishing Ravenna as a capital. Justinian is also credited with setting the foundation for the modern-day legal system with his Corpus Juris Civilis (“Corpus of Civil Law”). The blemish on his record comes with the Nika riots, an outbreak by the nobility in a vain attempt to overthrow Justinian from power, owing to his modest upbringing. This 9-day period of destruction was one of the main catalysts for rebuilding the Hagia Sophia, a structure that stands to this very day.
During an infamous period of Byzantine history known as the Iconoclasm, the veneration of religious figures in the form of idols or artwork featuring their likenesses had been forbidden. This period was initiated by Leo the Isaurian in AD 726 and lasted until 787, when it was revoked by Irene, the acting regent in the stead of her son, Constantine VI upon the death of her husband, Leo IV. Irene reinstated religious iconography and she eventually became the first official Empress of the Byzantine empire following the death of her son in AD 795. Some speculate she was also on the verge of accepting a marriage proposal from Charlemagne after he had declared himself Holy Roman Emperor, which very well might have reunited the whole of Rome and Byzantium into one empire yet again. However, her servants had her deposed and sent to Lesbos before such a marriage could be realized.
Serving as the last emperor of the Byzantine empire, Constantine XI had succeeded John VIII and oversaw the reoccupation of the Peloponnesus, the first time it had been in the fold of the Byzantine empire in over 200 years. In an effort to muster considerable defenses against a threatening Ottoman empire, Constantine XI finalized a Church union with the Peloponnesus region initialized by his predecessor despite great discord among his subjects on the matter. In the end, little aid came to Constantinople anyway, and Constantine XI died in defense of the city as it came under the rule of the Ottoman Turks, thus officially ending the reign of the Byzantine empire in 1453.