alamanni alans alaric i angles barbarian battle of tours bulgars burgundians byzantine empire byzantium caucasus climate change dark ages decadence decline of the roman empire dictionary of the middle ages early middle ages eastern europe eurasian avars europe franks frisians gaul german language gibraltar gothic and vandal warfare goths hispania historical migration history of western civilization human migration huns iberian peninsula jordanes joseph strayer jutes khazars late antiquity lombards lombardy medieval demography migration period pessimum migration period art mongol empire moors muslim conquests ostrogoths overpopulation plague of justinian reidgotaland romantic nationalism romanticism saxons slavic peoples suebi tatar invasions theodoric the great turkic migration turkic peoples vandals viking visigoths walter pohl western roman empire