On this day in 966, after his marriage to the Christian Dobrawa of Bohemia, pagan ruler of the Polans Mieszko I was baptised and converts to Christianity. The event is considered to be the founding of the Polish state and the entry of Poland into the community of western European Latin rite Christian states.
As most high-ranking marriages historically were, Mieszko’s was a political alliance and a political, rather than spiritual, conversion. Some two years before his conversion, the duke of Poland began negotiations with the Bohemian ruler Boleslav I the Cruel. Those negotiations resulted in Mieszko marrying Boleslav’s daughter, Dobrawa, sometime in 965. Because she was Christian, Mieszko was to be baptized. The act would bring his state closer to the Czechs, decrease the likelihood of attacks from German margraves invading on the pretense of bringing Christianity, and neutralize the power of Poland’s influential pagan priests, who were blocking Mieszko’s efforts to centralise Polish rule. Though the exact date is unknown, Mieszko was baptized on or around 14 April 966.
In undergoing Baptism, Mieszko effectively baptised the entire Polish state. The consequences were considerable. Poland entered the community of western European Latin rite Christian states. Furthermore, the Holy Roman Empire–or any other Christian country–theoretically had no right to attack Poland under pretext of bringing Christianity to the Poles, as the Duke himself was now a Christian. Though the pagan priest caste likely organized many rebellions and it was centuries before the majority of Poles followed suit and converted, Mieszko’s baptism also invited the spread of Latin culture and literacy into Poland. The Christianisation of Poland also restructured the state’s power elite, downgrading traditional tribal elders and pagan priests and upgrading incoming clergy who helped education, culture, and diplomacy flourish in Poland.
By the 13th century, Roman Catholicism was the dominant religion in Poland. To this day, Poles celebrate the day Christianity was introduced to Poland with large festivities.