 Zuckerman argues that Ignatius sent his archbishop to Rus' in about 870, while Dmitry Obolensky inclines to accept 874 as the date of the definitive Christianization.Zuckerman further reasons that the Christianization of both Bulgaria and Rus' was triggered by the adoption of Judaism by their chief enemy, Khazaria, in the late 8th or early 9th century.Although Byzantine sources provide the most detailed account of the 9th-century Christianization of the Rus', the contemporary Muslim authors seem to corroborate their evidence.