X. East: Ohrid (843-1204)

The end of the second iconoclasm in 842/3 heralded a new epoch of resurgence for Constantinople and Eastern Orthodox Christianity. Emperor Michael III come to the throne, followed by Basil I and the Macedonian dynasty which lasted into the eleventh century. Photius the Great, a former high-ranking civil servant, served as Patriarch (860s), later followed by Nicolas Mysticus (tenth century). During this period Constantinople held her enemies at bay and expanded her influence. 

By far the greatest achievement of this time was the successful missionising of the Slavic peoples. The invitation from Moravian ruler, Rastislav, came from a nation that had already embraced Christianity, preferring to join the ecclesiastical orbit of Constantinople and specifically requesting a Slavonic liturgy. Cyril and Methodius, Enlighteners of the Slavs, were dispatched in 863. Bulgaria was Christianised about the same time, first via the medium of Greek, and then likewise adopting the Slavonic liturgy. After Cyril's death at Rome in 867, it was Methodius who continued the work. And his followers, the Five, took refuge in Bulgaria. The Cyrillic alphabet, simpler than the Glagolithic script, is probably the work of one of the Five, Clement of Ohrid. It was from Ohrid (photo - GallopAroundTheGlobe), and also Preslav, centres of Orthodox Chrisitanity in Bulgaria, that, men were sent out to teach and convert the Serbs. Bulgaria also exercised influence on Kievan Rus, whose rulers Olga and her grandson Vladimir were converted in the tenth century, followed by the whole nation. Meanwhile the Balkan areas inside the Imperial limes such as southern Greece were reclaimed and re-evangelised by many, including evangelist-monk Nikon Metanoite. 

The missionary work of the church became a bone of contention between the western Catholic church of Rome and the Eastern Orthodox church of Constantinople, each competing with the other for "spheres of influence". Many areas switched allegiance several times - with what had been the Theodosian line, dividing east and west halves of the Roman Empire, moving back and forth over time. In fact, Moravia ended up within the orbit of the western Catholic church, as did Hungary - not to mention Poland and Croatia, which had never been Eastern Orthodox. By contrast, Bulgaria and later Kievan Rus became centres of Eastern Orthodoxy. The metropolitan bishop of Ohrid in the twelfth century, Theophylact (1050-1107), was a leading Bible scholar, and produced a commentary on the whole Bible. 

Initially, Eastern Orthodoxy was a "foreign religion" in these newly converted nations, such as Kievan Rus'. However, over time, Eastern Orthodoxy became indigenised with local saints such as martyrs Boris and Gleb, homegrown bishops such as Hilarion, Christian history in the form of a Chronicle composed by Nestor, preachers such as Cyril of Turov (1130-1182), as well as a gradual accumulation of local Christian experience, particularly the humble acceptance of suffering in imitation of Christ ("Russian kenoticism"). 

The differences between east (Constantinople) and west (Rome) over the concept of the Trinity (encapsulated in the words "and from the Son" or "Filioque" used the western church) and the role of the Roman Pope (first among equals, as understood in the east, or head of the whole church, as understood in the west) led to the temporary Photian schism 863-867 and then to the permanent schism of 1054. 

Meanwhile, in 963 the first monasteries were founded on Mount Athos, and this become the centre of Eastern Orthodox monasticism (replacing Studium). In Kievan Rus, the the great Kiev Pechersk Lavra founded in 1051 became the monastic centre. Having clarified the major issues of Christology by 843, the church turned its mind and attention to the mystic knowledge of God and the process of theosis (participation in the divine energies, akin to sanctification-glorification). In the words of Irenaeus, "God was "humanised", so that humans might be made be deified." A leading figure in this was Simeon the New Theologian (949-1022). By the practice of "mental prayer" he sought and attained the "vision of light", a mystical experience of knowing God in a way transcending understanding. He wrote, "... it is through death and the resurrection that God in His foresight has given us the Kingdom, incorruptibility, the totality of life eternal. Given these conditions, we unquestionably become partakers of the good things to come, that is, incorruptible, immortal, sons of God, sons of the light and of the day, inheritors of the Kingdom of Heaven, since we carry the Kingdom within."

A different, indeed ion some ways opposite approach, was taken by Michael and Italus Psellus, who applied reason to theology, taking a philosophical approach along the lines of Platonism. This led them to speak of the eternity of the soul and to deny a material resurrection of the body. Italus' condemnation by the church in 1076/7 and 1082 reflects Eastern Orthodoxy's different, more mystical approach to theology. 

The military defeat at Manzikert in 1071 marked a turning point in the fate of Constantinople with the rise of the Turks as the dominant power in the Middle East, eclipsing the Arabs. By 1176 Constantinople was clearly in decline and in 1204 it was sacked by the western Christian Crusaders, an event which made the schism even more permanent.