What are the three ways that civilization in western Europe declined after the Roman Empire fell?

After the fall of the western part of the Roman Empire, learning took a diminished role. Education dramatically declined. There was instability and wars between the Germanic peoples who conquered this part of the empire. As a result, trade declined and so did the towns. There was a population migration to the countryside, which became the focus of political and military power. Rural castles became the strongholds of the new landowning aristocracy and the knights.

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