We’re all taught in school that the Roman Empire ended in 476 A.D., the year that a German tribe under the leadership of a local chieftain named Odoacer deposed the last Roman Emperor in the West, one Romulus Augustus. Well, 476 is as good a year as any, but in fact Germanic tribes had been stomping through Italy for over a hundred years, by then, and the city itself had been invaded and sacked as early as 410 A.D. The truth is that it hardly mattered. The Empire had really left Rome in the early 300s.
Constantine the Great captured the city of Rome on his way to capturing the whole Roman Empire, but he never really lived there. Once he had consolidated his control over both the Eastern and Western wings of the Empire, he built a “New Rome”, named for himself (Constantinople) near a little old Greek town named Byzantium. Byzantium (and Constantinople) were located in what was, and had been for over 500 years, Greece. Today, it’s Turkey. They kept calling it “The Roman Empire” for many years, even after they stopped speaking Latin and switched to Greek. Scholars sometimes refer to the later, Eastern Empire as “Byzantine”, but the Emperors never did. They called themselves “Caesar” and their Empire “Rome” until they finally fell to Islam in May of 1453. So, Rome actually fell in 1453, right? Not exactly.
You see, in the “old” Rome, even though the civil government was in the hands of German invaders, there was a competing religious power. At the Council of Nicaea, in 325, as a way to get a “handle” on the feuding Bishops around the Empire, Constantine had taken two fateful actions. First, he integrated the Episcopal leadership of the Church into the regular Roman government. That is, whereas before 325, there was no formal church “chain of command” above “Bishop” (each Church or group of Churches had its own Bishop, as Paul makes clear in several of his letters), after that date, every Bishop was given a specific geographic area in which he was the supreme religious authority. The empire already had such a political unit, called a Diocese. So, even today, we have Bishops who are in charge of Dioceses. Constantine also set up ranks above “Bishop”: for example, “Archbishop”, and in each large group of Dioceses, he selected one large city to be both the governmental and the religious center. He called the religious rulers of these cities “Metropolitans”. Three “Metropolitans” were considered to be of especially high rank, those of Rome, Antioch and Alexandria. These supreme rulers were named “Patriarchs”. Later, two more Patriarchates were created, one in Constantinople, itself, and one in Jerusalem. These five each worked directly for the Emperor in administering his Church and each performed certain civil duties, as well. “Patriarch” is a Greek word meaning “to rule a family”, and is built around the word “patria”, which means “father”. Eventually, in Italy and the West, the Greek “patriarch” became the Latin “il Papa”, which means the same thing. English speakers Anglicized it to “Pope”.