The Frankish king Clovis (481-511) married a Catholic Burgundian princess. After experiencing a battlefield conversion (like that of the Emperor Constantine), he required all his subjects to accept Catholicism rather than Arian Christianity.
Pope Gregory I: Spiritual papacy and took over the governments role, fed the poor, sent missionaries to England, defended Rome from barbarians, promoted Benedictine monasticism
Survived thanks to its strong defenses, including a secret weapon known as "Greek fire," which burned even on water and could devastate enemy forces that came near the walls.
Muslims gave Romans: Astrolabes, paper, algebra, number of 0
Needed money to fight England and Flanders
Provinces in the Balkans were harassed by Avars (a Turkic group from central Asia)