LEO OF ACHRIDA. - Byzantine bishop and promoter of the Eastern Schism. Under the influence of the Greek patriarch Michael Cerularius (v.), L. sent a letter in 1053 to Bishop John of Trani (in Apulia). This document was drawn up while negotiations were still underway between the Byzantine court and Pope Leo IX for a joint expedition against the Normans who were then invading southern Italy, still under Byzantine rule, and for the acceptance of the preliminary condition set by the Holy See, namely the unity of the Byzantine Church with the Roman Church.
The agreement was hindered by the Byzantine patriarch; although he wrote a peaceful letter to the Pope under the influence of his Emperor, he cunningly induced L. to write an anti-Latin letter. In this letter, four accusations were made against the Roman Church: 1) the use of unleavened bread; 2) the fasting on Saturday; 3) the eating of animals that had died by suffocation; 4) the omission of the Alleluia during Lent (Latin translation by Cardinal Humbert of Silva Candida: PL 143, 744-69). The version was delivered to Pope Leo IX, who had it rejected by the aforementioned cardinal.