Cyril And Methodius, supposed to have been brothers, apostles of the Slavs, of whom the former, born in Thessalonica about 820, died in Rome, Feb. 14, 869; the dates of the birth and death of the latter are unknown. The former received in baptism the name of Constantine, by which he was known until he embraced the monastic profession, or, as others think, until he was consecrated bishop in Rome, when he assumed the name of Cyril. His father, who was of senatorial rank, sent him to be educated in Constantinople, where his knowledge of languages and his varied erudition gained him the surname of Philosophos (the learned) and the custody of the public library. He had become a monk and received priest's orders when Methodius, who had attained the rank of general in the imperial army, entered the same monastery. In 848 the empress regent Theoflora received a deputation from the Khazars, who held the Crimea and neighboring countries, and asked for missionaries to instruct them in the Christian religion. Cyril was chosen by the empress for this mission. He spent some time in the Crimea, to acquire familiarity with the Slavic tongue, succeeded in bringing to the Christian faith the khan of the Khazars, and returned to Constantinople, leaving several priests to continue the good work.

Kadislas, prince of the Moravians, having heard of the success of Cyril among the Khazars, also sent to Theodora asking for missionaries. This time she sent both the brothers, providing them with all that was necessary for their journey. This missionary enterprise also embraced Bulgaria, Serbia, and Pannonia. They brought with them a translation of the Gospels into Slavic (old or church Slavic), and, it is said, the relics of St. Clement (Clemens Romanus), discovered in the Crimea. The Moravians received the missionaries with great joy, and the work of instruction went on rapidly, Cyril having adapted the Greek and Roman alphabets to the Slavic idioms. As the beginning of Christianity in Moravia had been due to priests sent from Germany, the metropolitan of Salzburg and his suffragans took offence at the success of the Greeks, and at the use of the vulgar tongue in the celebration of mass. They complained to the pope, and Nicholas I. summoned the brothers to answer these charges. On their arrival in Rome Adrian II., who had meanwhile succeeded Nicholas, received the missionaries with great favor, heard their story, approved all they had done, and raised them both to the episcopal dignity, appointing Methodius metropolitan of Moravia, but assigning no particular see to Cyril. In the winter of 868 Cyril, when about to return to the field of his labors, sickened and died ,in one of the monasteries of Rome. Methodius was doomed on his return to witness a sad change.

Radislas in 870 was defeated by Louis of Germany, and shut up in a monastery after having had his eyes put out. Swatopluk, who took his place, showed himself at first a tyrant and an enemy of Christianity. Methodius, finding expostulation unavailing, excommunicated the prince, and was expelled from Moravia. Swatopluk repented some time afterward, sent to the exiled archbishop soliciting his return, and promised to repair the evils he had caused. Methodius was again accused at Rome by a synodal letter signed by the archbishop of Salzburg and his suffragans, and John VIII. wrote to Swatopluk asking that Methodius should once more proceed to Rome. This second journey, in 880, procured him only a still more honorable reception from the pope, a renewed approbation of his conduct in the establishment of the Slavic liturgy, and a confirmation of his prerogatives as metropolitan. Duke Borzivoy of Bohemia, having come to visit Swatopluk, his suzerain, was treated with indignity because he was not a Christian. The kind words of Methodius soothed him, and his instructions soon enlightened him. He embraced Christianity, converted his wife, and engaged Methodius to assist in converting his people.

This change did not happen without a civil war in which the Christians were finally victorious, and Borzivoy was left free to carry out his intentions peacefully. The churches of St. Peter and St. Paul and of Our Lady in Prague are said to have been founded by him. Methodius is supposed to have made a third pilgrimage to Rome, and died there. - The 1000th anniversary of the foundation of the Slavic churches was celebrated in 1864 both in Bohemia and Moravia. An edition of Cyril's version of the Scriptures was printed at Ostrog in 1581, under the auspices of the palatine of Volhynia; it is in the so-called Cyrillic character. There is also a Glossarium Cyrilli in the work entitled Vetus Lexicon Grceco-La-tinum, cum Notis Vulcanii (fob, Leyden, 1600). Among the biographers of these saints are Stredowski, who has a life of Cyril and Methodius in his Sacra Moravia Historia (4to, Sulzbach, 1710), and Philaret, bishop of Riga (German translation, 1847). See for particulars Rohrbacher's "Church History," vol. viii., and Wattenbach, Beitrage zur Geschichte der christlicJien Kirche in Mahren und Bohmen (Vienna, 1849).