Great Schism, 2 divisions in the Christian Church. The first was the breach between the Eastern and Western churches. Long-standing divergences in tradition, combined with political and theological disputes, came to a head in 1054 when Pope Leo IX sent legates to refuse the title of Ecumenical Patriarch to the patriarch of Constantinople and to demand acceptance of the filioque (“and from the Son”) clause in the Nicene Creed. The patriarch refused and rejected the claim of papal supremacy. Reciprocal excommunications and anathemas followed. Later councils were unsuccessful in healing the breach. The second Great Schism was the division within the Roman Catholic Church (1378–1417) when there were 2 or 3 rival popes and antipopes, each with his nationalistic following. The Council of Constance ended the schism by electing Martin V sole pope.