[Sawdring]

You are forgetting the Byzantine Empire when you say no high civilization existed after the Roman Empire. This empire lasted until about 1450 when the Ottomans conquered Constantinople.

[muawiyah]

"then it fragmented for good" ~ and whatever they were doing in the Eastern Empire, that was their business from then on. Took Provence, Gaul, Spain, etc. an awful long time to recover and then only in our own time did they figure out any sort of political unity.

Tellingly, it involves mostly standards ~ which is what Rome was all about as well.