Leo of Ohrid
Leo of Ohrid (died 1056) was a leading 11th-century Byzantine churchman as Archbishop of Ohrid and advocate of the Patriarchate of Constantinople's views in the theological disputes with the See of Rome, which culminated in the East–West Schism of 1054.
Under Patriarch Michael Keroularios (1043–59), Leo was sent as the spokesman of Constantinople to theological debates with clergymen representing the Pope of Rome in southern Italy. He reiterated his views in a 1053 letter to the bishop John of Trani, which was however addressed to the Pope and all Latin bishops. In this letter, "Leo for the first time shifted the religious estrangement between East and West toward liturgical and disciplinary issues" (J. Meyendorff), and condemned various practices of the Western Church such as the eating of strangled meat, with blood, the fasting on Sundays, or various minor issues of ritual. The most important point of friction, however, was the Western use of unleavened bread (azyma) for celebrating the Eucharist, which provoked a running argument carried out in a series of letters with Cardinal Humbert of Silva Candida, which finally led to Humbert's mission to Constantinople in 1054 and the finalizing of the Great Schism between Rome and the East through their mutual anathemas, resulting in the existence as separate Churches of the Roman Catholic Church and the Eastern Orthodox Church.