Askold and Dir
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.