“When the Roman Empire fell in the fifth century, the strong trustee families of the barbarian tribes replaced the weak, atomistic Roman families as the foundation of society.
The Roman Empire didn’t fall in the fifth century, the Western Roman Empire fell.
The Eastern Empire kept plugging along for just about a thousand more years.”
The eastern Roman empire was for all basic purposes destroyed by Mohammed in the 7th. Century. What pitiful remnant — Byzantium — that was left was finally finished off by Mehmet the Second in 1492 when he utterly destroyed Constantinopal.
1453
Commonly believed, but quite inaccurate.
The Byzantine Empire rebounded quite nicely from its confrontation with the Arab Empire, recovering much of the territory lost to the Muslims in the 9th thru 11th centuries. During this period it was generally much the strongest Christian power.
Common sense alone should tell us that no nation is "destroyed" in the 7th century but still somehow manages to hang on for another 800 years.
The Byzantine Empire has a long history of getting no respect in the West, but it is a fact that Western civilization sheltered from the Muslims behind it for at least 500 years, giving Western civ a chance to get going. Without the Eastern Roman Empire Europe would probably have fallen to Islam.