In Europe, the decline of the Western Roman Empire. For the formerly Roman area, there was 20 percent decline in population between 400 and 600, or a one-third decline for 150-600.
The Anglo-Saxons in England had started to convert from Anglo-Saxon polytheism after the arrival of Christian missionaries around the year 600.
The Early Middle Ages marked the beginning of the cultural distinctions between Western and Eastern Europe north of the Mediterranean. Influence from the Byzantine Empire impacted the Christianization and hence almost every aspect of the cultural and political development of the East from the preeminence of Caesaropapism and Eastern Christianity to the spread of the Cyrillic alphabet. The turmoil of the so-called Barbarian invasions in the beginning of the period gradually gave way to more stabilized societies and states as the origins of contemporary Eastern Europe began to take shape during the High Middle Ages.
Turkic and Iranian invaders from Central Asia pressured the agricultural populations both in the Byzantine Balkans and in Central Europe creating a number of successor states in the Pontic steppes.