Invasions from east and west
The Crusades
After the Battle of Manzikert (1071) in eastern Asia Minor, Byzantium lost most of Anatolia to the Turks and ceased to be a world power. Partly solicited by the Byzantines, the Crusades proved another disaster: they brought the establishment of Latin principalities on former imperial territories and the replacement of Eastern bishops by a Latin hierarchy. The culminating point was, of course, the sack of Constantinople itself in 1204, the enthronement of a Latin emperor on the Bosporus, and the installation of a Latin patriarch in Hagia Sophia. Meanwhile, the Balkan countries of Bulgaria and Serbia secured national emancipation with Western help, the Mongols sacked Kiev (1240), and Russia became a part of the Mongol empire of Genghis Khan. The Byzantine heritage survived this series of tragedies mainly because the Orthodox church showed an astonishing internal strength and a remarkable administrative flexibility.
Until the Crusades, and in spite of such incidents as the exchanges of anathemas between Michael Cerularius and the papal legates in 1054, Byzantine Christians did not consider the break with the West as a final schism. The prevailing opinion was that the break of communion with the West was due to a temporary take over of the venerable Roman see by misinformed and uneducated German “barbarians” and that eventually the former unity of the Christian world under the one legitimate emperor—that of Constantinople—and the five patriarchates would be restored. This utopian scheme came to an end when the Crusaders replaced the Greek patriarchs of Antioch and Jerusalem with Latin prelates, after they had captured these ancient cities (1098–99). Instead of reestablishing Christian unity in the common struggle against Islam, the Crusades demonstrated how far apart Latins and Greeks really were from each other. When finally, in 1204, after a shameless sacking of the city, the Venetian Thomas Morosini was installed as patriarch of Constantinople and confirmed as such by Pope Innocent III, the Greeks realized the full seriousness of papal claims over the universal church: theological polemics and national hatreds were combined to tear the two churches further apart.
After the capture of the Constantinople, the Orthodox patriarch John Camaterus fled to Bulgaria and died there in 1206. A successor, Michael Autorianus, was elected in Nicaea (1208), where he enjoyed the support of a restored Greek empire. Although he lived in exile, Michael Autorianus was recognized as the legitimate patriarch by the entire Orthodox world. He continued to administer the immense Russian metropolitanate. The Bulgarian church received from him—and not his Latin competitor—its right for ecclesiastical independence with a restored patriarchate in Trnovo (1235). It was also with the Byzantine government at Nicaea that the Orthodox Serbs negotiated the establishment of their own national church; their spiritual leader, St. Sava, was installed as autocephalous archbishop of Serbia in 1219.
The Mongol invasion
The invasion of Russia by the Mongols had disastrous effects on the future of Russian civilization, but the church survived, both as the only unified social organization and as the main bearer of the Byzantine heritage. The “metropolitan of Kiev and all Russia,” who was appointed from Nicaea or from Constantinople, was a major political power, respected by the Mongol Khans. Exempt from taxes paid by the local princes to the Mongols and reporting only to his superior (the ecumenical patriarch), the head of the Russian church acquired an unprecedented moral prestige—though he had to abandon his cathedral see of Kiev, which had been devastated by the Mongols. He retained ecclesiastical control over immense territories from the Carpathian Mountains to the Volga River, over the newly created episcopal see of Sarai (near the Caspian Sea), which was the capital of the Mongols, as well as over the Western principalities of the former Kievan empire—even after they succeeded in winning independence (e.g., Galicia) or fell under the political control of Lithuania and Poland.