The Christian East and West had been drifting apart for centuries — in language (Greek and Latin), in custom, in theology, and above all in the question of authority: how far did the bishop of Rome's primacy extend? A particular flashpoint was the filioque, the Western addition to the Nicene Creed stating that the Spirit proceeds 'and from the Son.'
In 1054 a papal delegation and the Patriarch of Constantinople exchanged mutual excommunications. At the time it seemed one quarrel among many; in hindsight it marked the formal break between the Roman Catholic Church and the Eastern Orthodox Church.
Theologos describes the theology of that division descriptively on the Roman Catholic and Eastern Orthodox tradition pages, in each tradition's own framing. The 1054 break has never been formally healed, though the mutual excommunications were lifted in 1965.
