Ukraine on their way to preach to the Khazars. Sent from Constantinople at the request of the ruler of Great Moravia, these brothers would add to foundation of Christianity in Ukraine by creating the Glagolitic alphabet, a precursor to the eponymous "Cyrillic script", which enabled the local population to worship God in Old Church Slavonic, a language closer to the vernacular Old East Slavic language than the Greek used to worship in Constantinople, or Latin in the west. In response to local disputes with clerics of the Latin Church, Cyril and Methodius appealed in person to the Bishop of Rome in 867, bringing with them the relics of Pope St. Martin from Chersonesos. Their labors and request were met with approval, and their continued efforts planted the Christian faith into Ukrainian Rus. By 906, they had founded a diocese in Peremyshl, today a diocese of the Ukrainian Greek Catholic Church in Przemyśl, Poland. Their efforts, and those of their apostles, led to the translation of Christian Scriptures and service (liturgies) from Greek to Slavonic, and the eventual development of the modern Cyrillic alphabet. Early Rus' period By the 9th century, it is known that the Slavic population of western Ukraine (likely the White Croats) had accepted Christianity while under the rule of Great Moravia. However, it was the East Slavs who came to dominate most of the territory of present-day Ukraine, beginning with the rule of the Rus', whose pantheon of gods had held a considerable following for over 600 years. Following the 860 assault on Constantinople by Rus' forces under the command of Askold and Dir, the two princes were baptized in that holy city. Returning to Kyiv, the two actively championed Christianity for a period of 20 years, until they were murdered by the pagan Prince Oleg in the inter-princely rivalry for the Kyiv throne. Patriarch Photios purportedly provided a bishop and priests from Constantinople to help in the Christianization of the Slavs. By 900, a church was already established in Kyiv, St. Elijah's, modeled on a church of the same name in Constantinople. This gradual acceptance of Christianity is most notable in the Rus'-Byzantine Treaty of 945, which was signed by both "baptized" and unbaptized Rus'", according to the text included in the Primary Chronicle. Establishment of the Kyiv Metropolitan Christianity acceptance among the Rus' nobility gained a vital proponent when Princess Olga, the ruler of Kyiv,