In many ways, the post-Roman Germanic kingdoms of Western Europe and the Byzantine Empire shared a similar fate. Both saw a sharp ruralization, that is, a decline in the number of inhabited cities and the size of those cities that were inhabited. Both saw plunges in literacy. And both saw a state that was less competent—even at tax collection. Moreover, the entire Mediterranean Sea and its environs showed a steady decline in high-volume trade across the ocean, a decline that lasted for nearly two and a half centuries. By around the year 700, almost all trade was local.
But there remained profound differences between Byzantium and the Germanic kingdoms of Western Europe. In the first place, although its reach had shrunk dramatically from the days of Augustus, the imperial state remained. Although the state collected less in taxes and issued less money than in earlier years, even in the period of the empires’ greatest crisis, it continued to mint some coins and the apparatus of the state continued to function. In Western Europe, by contrast, the Germanic kingdoms gradually lost the ability to collect taxes (except for the Visigoths in Spain). Likewise, they gradually ceased to mint gold coins. In Britain, cities had all but vanished, with an island inhabited by peoples living in small villages, the remnants of Rome’s imperial might standing as silent ruins.
The post-Roman world stands in contrast to post-Han China. Although the imperial state collapsed as it had in Rome, in China, literacy never declined as drastically as it had done in the Roman Empire, and the apparatus of tax collection and other features of a functional state remained in the Han successor states to an extent that they did not in either Rome or Byzantium.