July 16
Great Schism Begins in Constantinople
A papal legate’s public act of excommunication inside Hagia Sophia on July 16, 1054, crystallized centuries of theological, cultural, and political friction into the lasting division between the churches of Rome and Constantinople.
Summary
By the mid-eleventh century, longstanding tensions divided the Christian church over issues of papal authority, the filioque clause in the Nicene Creed, and liturgical practices. In 1054, Pope Leo IX sent Cardinal Humbert of Silva Candida as legate to Constantinople to address disputes with Patriarch Michael I Cerularius. On July 16, during a Saturday liturgy in Hagia Sophia, Humbert placed a bull of excommunication against the patriarch and his followers on the altar. Cerularius responded in kind, excommunicating the papal legates. Historians view this exchange as the symbolic start of the East-West Schism separating Roman Catholicism and Eastern Orthodoxy. The event crystallized centuries of cultural, political, and theological divergence between the Latin West and Greek East.
Context
By the eleventh century the Christian world had long been shaped by the division of the Roman Empire and the distinct trajectories of its Latin West and Greek East. Constantinople had risen as the political and ecclesiastical capital of the surviving eastern empire, while Rome retained its ancient prestige yet operated in a fragmented political landscape dominated by emerging kingdoms and the Holy Roman Empire. These structural differences fostered contrasting views of church authority: the papacy increasingly asserted universal primacy, whereas eastern Christians favored a collegial model among the five patriarchates.
What Happened
Tensions sharpened in 1053 when Patriarch Michael I Cerularius closed Latin-rite churches in Constantinople and criticized western practices such as the use of unleavened bread in the Eucharist. Pope Leo IX responded by dispatching three legates—Cardinal Humbert of Silva Candida, Frederick of Lorraine, and Peter of Amalfi—to Constantinople. Their mission combined diplomatic overtures regarding Norman threats in southern Italy with demands that Cerularius recognize papal supremacy and abandon certain eastern customs. The patriarch proved unwilling to yield on either point.
Aftermath
On July 16, during the Saturday liturgy in Hagia Sophia, Humbert laid a bull of excommunication against Cerularius and his supporters on the high altar before departing. Cerularius promptly convened a synod that anathematized the legates personally and burned the document. Leo IX had already died the previous April, rendering the legates’ authority technically lapsed, yet the mutual condemnations stood and relations between the two sees deteriorated rapidly.
Legacy
Although contemporaries viewed the exchange as one episode among many, later historians came to regard 1054 as the symbolic beginning of the East-West Schism. The breach widened dramatically with the Fourth Crusade’s sack of Constantinople in 1204 and has shaped ecclesiastical identities, political alignments, and ecumenical efforts ever since. Formal lifting of the 1054 anathemas occurred only in 1965, without restoring full communion.
Why It Matters
The schism permanently divided Christianity into Western and Eastern branches, shaping European politics, crusades, and church-state relations for the next millennium. It influenced the fall of Constantinople in 1453 and ongoing ecumenical efforts today. The divide affected alliances during the Ottoman expansion and Reformation-era conflicts.
Related Questions
What were the main issues dividing the Eastern and Western churches before 1054?
Disputes centered on papal claims to universal authority, the addition of the filioque clause to the Nicene Creed in the West, differing Eucharistic practices such as leavened versus unleavened bread, and contrasting liturgical customs.
Why is the 1054 exchange considered the start of the Great Schism even though Leo IX had already died?
Although the legates technically lacked authority after the pope’s death, the public mutual excommunications became the enduring symbol of the institutional rupture between Rome and Constantinople.
How did political events in Italy contribute to the crisis?
Norman conquests in southern Italy created overlapping claims of jurisdiction between the papacy and the Byzantine emperor, prompting Leo IX to seek Constantinople’s cooperation while simultaneously pressing ecclesiastical demands.
What long-term effects did the schism have on relations between East and West?
The division complicated alliances against external threats, contributed to the Fourth Crusade’s attack on Constantinople in 1204, and left a lasting separation between Roman Catholicism and Eastern Orthodoxy that persists today.
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Sources
- July 16 - Wikipedia, Wikimedia Foundation. Accessed 2026-07-02.
- On This Day - What Happened on July 16, Encyclopædia Britannica. Accessed 2026-07-02.