THE SEVEN AGES OF HISTORY.
Shakespeare wrote about the "seven ages of man" so it may be possible that the common belief among Evangelical and Protestant believers, that there are seven ages of history outlined in the Book of Revelation was known at that time? That being speculation the description of the seven churches in the book pf Revelation is said to be a basic sevenfold chart of history there to plainly see for those spirtual enough to understand it, just as the 4 beasts in Daniel 7 chart the history of 4 world Empires, and even help predict the final world Empire of the Beast.
THE BYZANTINE EMPIRE:
After the death of Constantine there was a significant change to his tolerance of all religions as the fake Faith of churchianity, empowered by the new binding together of the church and state in the scarlet and purple heresy, began to crush even further freedom of speech and belief. The time period is rather loosely termed by the Orthodox "The Byzantine Empire". After the great Schism between Romanism and Orthodoxy some would say "Christendom" was the term applied. It might be an area of contention where the time period referred to as "The Byzantine Empire" should be placed in the descriptors of the 7 churches, in the Pergamos time period (the binding of the church and state) or that of Thyatira, but the dominating symbol of Jezebel in the Thyatira time zone, that is a clear symbol of Rome and Romanism, I would say puts the concept of "The Byzantine Empire" largely before the great Schism, but as Rome grew in power it still existed. The Orthodox say the Byzantine Empire lasted for a thousand years. Sometimes you cannot draw an exact dividing line on the disintegration of an Empire, it can be phased slowly out.
The military tactics of Rome, the Triplex Acies (three layers of various troops with specific ranks and purposes) is in religious terms copied spiritually, where layers of religious deception are use, to subjugate the masses and conquer them.
THE so called DARK AGES:
The Orthodox insistence that there were definitely no Evangelical or Protestant (for a testimony) type churches or communities in the so called "Dark Ages" or middle ages is based on ignoring the whole characteristics of that time period.
Quote from OED (Oxford English Dictionary)
the period of European history from the fall of the Roman Empire in the West (5th century) to the fall of Constantinople (1453), or, more narrowly, from c.1000 to 1453.
The earlier part of the period ( c.500– c.1100) is sometimes distinguished as the Dark Ages, while the later part (c.1100–1453) is often thought of as the Middle Ages proper. The whole period is characterized by the emergence of separate kingdoms, the growth of trade and urban life, and the growth in power of monarchies and the Church. The growth of interest in classical models within art and scholarship in the 15th century is seen as marking the transition to the Renaissance period and the end of the Middle Ages.
Urban (city) life as we know it today was growing, but communities were largely scattered. Though the 2nd Babylonian Captivity was growing, the actual total dominance on such scattered communities would not be complete. Feuding and vendettas were common, the protection of an organised state described in Romans 13 was not in place, the history of such scattered communities looking after themselves is not recorded, yet Orthodoxy and Catholicism insist that though there were heretics murdered by the so called "church" at this time, no one could have been Evangelical in their beliefs.
It is interesting that the height of the combined forces of Romanism and Orthodoxy creating "Christendom" is also known as "The Dark Ages".
It is difficult to name the many so called "sects" in the period before the Reformation, as so little is known about them. The Waldensians for instance. What is known is they challenged sacraments
However that runs both ways? How do the Orthodox know they were or were not similar to modern Evangelicals, to the extent they can completely deny it?