Pope Gregory I (the Great)

Gregory was a Roman aristocrat who became a monk, then was drafted to be Pope, and during fourteen years in office (590–604) reorganised the Western church for the medieval world. He sent Augustine of Canterbury to convert the Anglo-Saxons, codified the chant that bears his name, wrote the Pastoral Care that every medieval bishop used as a manual, and held Italy together as the Roman state collapsed around him. The reason 'medieval' Christianity has the shape it does is largely his.