Slavorum Apostoli §24

²⁴ The Baptism of Poland in 966, in the person of the first historical sovereign, Mieszko, who married the Bohemian princess Dubravka, took place principally through the Bohemian Church, and by this route Christianity reached Poland from Rome in the Latin form. But the fact remains that the beginnings of Christianity in Poland are in a way linked with the work of the Brothers who set out from distant Salonika. Among the Slavs of the Balkan peninsula the efforts of the holy Brothers bore fruit in an even more visible way. Thanks to their apostolate the Christianity which had already for some time been established in Croatia was consolidated. Principally through their disciples who had been expelled from the area where they had originally worked the mission of Cyril and Methodius was confirmed and developed wonderfully in Bulgaria. Here, thanks to Saint Clement of Okhrid, dynamic centers of monastic life arose, and here particularly the Cyrillic alphabet developed. From here too Christianity moved to other territories, until it passed through neighboring Romania and reached the ancient Rus' of Kiev, and then spread from Moscow eastwards. In a few years, in 1988 to be exact, the millennium of the baptism of Saint Vladimir, Grand Duke of Kiev, will be celebrated.