Why Did the Christian Church Split?

The schism between the Orthodox and Catholic faiths began when the patriarch of Constantinople, Michael Cerularius, refused to acknowledge the supremacy of the Bishop of Rome (the pope), Leo IX, and was subsequently excommunicated in 1054. However, papal supremacy was but one of several issues that the east and west disagreed on.

While historians disagree on the importance of the following differences, all played a role in the split: differing views on iconoclasm, or the use of images of saints and other figures in worship; the west's preference for Latin versus the east's reliance on Greek; the use of unleavened bread in the west, which was considered to be an exclusively Jewish tradition in the east; and the coronation of Charlemagne as Holy Roman Emperor, which was seen as invalid in the east because of the continued existence of the Byzantine Empire.

It's also worth noting that there were several smaller splits in Christianity before 1054, such as the Monophysites who split from the church after the Council of Chalcedon in 451, as well as later schisms, such as the Protestant Reformation.