Answer: converted Slavs to Christianity (especially western Slavs).
Explanation: founder of Bohemian (Czech) first dynasty (Premyslids) Borivoj received Christianity from their hands in Great Moravia. He was the first Czech duke who successfuly introduced Christianity to the Czech lands. Today they both are remembered in the Czech rep. because there is an official feast of Cyril and Methodius (July, 5). Cyril was older of both brothers and died in Rome (869 AD), younger Methodius became archbishop and died in Great Moravia. Both were of Greek origin.
A secular view of the church is the church is trying to tie us down and keep us in the past by old traditions when everyone is moving on. When the church said we need to stick with traditon so we have solid ground to grow and glorify.
We certainly never saw him in person. But we sure knew the legend. He was the Olympic track champion who lost his gold medals because he played minor league baseball.
