The dispute about the authority of Roman bishops reached a climax in 1054 , when Michael I Cerularius tried to bolster his position as the " Patriarch of Constantinople " , seeming to set himself up as a rival of Pope Leo IX , as the Popes previously had forbidden calling Constantinople a patriarchate . The dispute ended when the Pope 's legate , Cardinal Humbert , excommunicated Cerularius and , in exchange , Michael excommunicated the papal legates . It was suspected by the Patriarch that the bull of excommunication , placed on the altar of Hagia Sophia , had been tampered with by Argyros , the commander of Southern Italy , who had a drawn-out controversy with Michael I Cerularius . Although this is commonly viewed as the " Great Schism " , historically the event did little to change the relationship between East and West at that time . Michael himself knew that the Pope was a prisoner of the Normans at the time that Humbert arrived , and by the time Michael was excommunicated Pope Leo had already died , voiding the papal legates of authority . Moreover , Michael did not excommunicate the Pope , nor even the Western Church , but only the papal delegation . It is probably more proper to point to the Massacre of the Latins of 1182 or the Sack of Constantinople by the Fourth Crusade in 1204 as more clear separation between the two Churches
Massacre of the Latins
Massacre of the Latins
Christianity in the 11th century