Charlemagne spread Christianity through conquests. He conquered a bunch of land and he spread Christianity to the conquered people, connecting Germanic, Roman, and Christian elements into an empire. He was crowned emperor by the Pope.
Clovis was the first Germanic leader to convert to Christianity. He turned his wars of aggression and conquest into holy wars against heretics and began working closely with the Pope.
He protected church property that resulted to Pope's encouragement loyalty to the king. By 511, Clovis had united the Franks into a kingdom.
To learn more, see Middle Ages, Influence of Christianity - World History International.
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