The Great Schism
This may designate either one of two unrelated events which disunited Christendom. The schism of 1054 (“Eastern Schism”) formally ruptured communion between the churches under the pope at Rome, Leo IX, and those under the patriarch at Constantinople,, until then considered second in the hierarchy. Already two very different churches, both culturally and theologically, they have since developed their separate ways: a Byzantine-Greek church became Eastern, Greek, and Russian Orthodoxy, while a Roman-Latin church became .
The schism of 1378-1417 (“Western Schism”), following the pope's Avignon residency (1309-77), divided allegiances in disintegrating Western Christendom between first two, then three, simultaneous popes, each excommunicating the other. A line with seat in Rome began with Urban VI, backed by the German Empire, England, Hungary, Scandinavia, and most of Italy. An Avignon line began with, backed by France, Naples, Savoy, Scotland, Spain, and Sicily. Attempts (1409) to end the schism brought a third Pisan line. Martin V's election (1417) ended the schism. The crisis partially arose out of tensions between the authority of the papacy and feudal monarchies, and of the papacy and cardinals.