The East-West Schism, also known as the Great Schism of 1054, marked the definitive break in communion between the Catholic Church in the West and the Eastern Orthodox Church. The schism was the culmination of long-standing theological, political, and cultural disagreements between the Greek-speaking East and the Latin-speaking West. Key issues included the inclusion of the Filioque clause in the Nicene Creed, the type of bread used in the Eucharist, the role of icons, and disputes over papal authority versus the status of the Patriarch of Constantinople.

Tensions escalated in 1053 when the Western Church attempted to impose Latin practices on Greek churches in southern Italy, leading to a series of retaliatory actions. In 1054, a papal legation led by Cardinal Humbert was sent to Constantinople not only to address these church disputes but also to seek military support against the Normans in Italy. The mission failed, and mutual excommunications were issued by Humbert and Patriarch Michael I Cerularius, though these were largely symbolic as they did not reflect a wider ecclesiastical consensus.

Despite the formal declarations, many ordinary Christians remained unaware of the depth of the schism, and relations between the two churches continued, albeit strained by political conflicts and the Crusades, particularly the Fourth Crusade’s sack of Constantinople in 1204, which deepened the division.

Efforts toward reconciliation have been ongoing, including the symbolic lifting of the 1054 excommunications by Pope Paul VI and Patriarch Athenagoras I in 1965. However, full communion has not been restored, and ecumenical efforts often face internal opposition. Relations today are marked by both continued dialogue and enduring division, with regular symbolic gestures and exchanges between the churches, underscoring a complex relationship that has evolved over nearly a millennium.