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
590 - 604
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
Roman Constantinople attacked by Arabs
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 influenced Romans
Muslims gave Romans: Astrolabes, paper, algebra, number of 0
Roman Constantinople attacked by the Fourth Christian Crusade
Philip IV of France (The Fair) focused on increasing revenue
1285 - 1314
Needed money to fight England and Flanders
Roman Constantinople attacked by Turks
Provinces in the Balkans were harassed by Avars (a Turkic group from central Asia)