Andrew Louth the background of the mutual anathemas: (From Greek East and Latin West pp. 306-8):
In the 1030s the Byzantines had made an attempt to reconquer Sicily, but only recovered the eastern coast. Traditionally, this part of the word–Sicily and “Magna Graecia,” “Great Greece”–was Greek-speaking; it was Greek-speaking Byzantine Christianity that had survived Muslim rule and Byzantine Christianity that was restored. However, it had originally come under the jurisdiction of the Pope, who had considerable landholdings there, but in the eight century, as a result of the pope’s resistance to the imperial will over iconoclasm, the jurisdiction of this area had been transferred to the patriarchate of Constantinople (along with the are of the Balkans known as Illyricum). As we have seen, the pope’s loss of jurisdiction over these areas (and of revenue, too) had long been a bone of discontention between Pope and Emperor. The coming of the Normans disturbed an already fragile situation. They established themselves throughout southern Italy, building castles from which they plundered and then sought to rule the region; later in the century they succeeded where the Byzantines had failed in driving the Arabs out of Sicily.
The initial response of both Pope and Emperor to the Norman presence in Italy was one of alarm. Michael Keroularios, patriarch of Constantinople from 1043 to 1058, sent a friendly letter to Pope Leo IX proposing an alliance against the “Franks.” Nothing came of that initiative. In 1053, both the Byzantine and papal forces suffered serious defeats at the hands of the Normans; Pope Leo was taken prisoner and held in Benevento. As they settled in southern Italy, the Normans encountered Greek Christians following Greek customs, different from the Latin ways. Tolerance was not a virtue much respected by the Normans (nor by many others in the Middle Ages): the Greek ways were suppressed and Latin customs introduced. The cult of Greek saints, for instance, was suppressed (just as the Normans in England suppressed the cult of many of the Anglo-Saxon saints), and devotion to more mainstream Latin saints encouraged, though a few local saints were saved by the efficacy of their miracles. One custom, however, sharply marked off Greek from Latin, and that was the kind of bread used in the eucharistic liturgy–leavened or unleavened–and there were other liturgical differences. There began, in southern Italy of the eleventh century, a different kind of encounter between Greek East and Latin West, which was to become more common over the next century or so. This was an encounter that affected ordinary people, for it concerned what they did when they worshipped. Hitherto, Latin and Greek practices had been geographically separate. Scholars–and merchants, used to local differences–had known about various differences between Eastern and Western Christians, but that was in the realm of theory. Now the differences were on the doorstep; ordinary people became aware of different customs and had to live with them, or not.
Although the pope had no love for the Normans, he could hardly object to their imposition of Latin practices. Christians in the Byzantine Empire, especially in the geographically closer, formerly independent Bulgaria, felt very differently. The suppression of Greek services, and the replacement of ordinary leavened bread in the Eucharist favoured by the Latins, was an affront. The archbishop of Ohrid, the senior Bulgarian bishop, Leo, wrote to John, archbishop of Trani in Apulia, arguing that unleavened bread (azyma in Greek) was not properly bread and that, therefore, the Latin Eucharist was not a genuine sacrament; furthermore, the use of unleavened bread was a Jewish practice, inappropriate for the sacrament of the New Covenant. Leo’s letter, at his request, was translated into Latin, Leo doubtless expecting the Italian episcopate to endorse his arguments. Earlier on Leo himself had been one of the clergy of Hagia Sophia in Constantinople, and was, indeed, the first Greek-speaking incumbent of the see of Ohrid. It has often been suspected that Leo’s letter was written at the behest of Patriarch Michael Keroularios–a charge explicitly made by Cardinal Humbert–but there is no direct evidence that such was the case. News of the suppression of Greek services in Apulia had, however, reach Constantinople, and the patriarch had retaliated by closing some, at least, of the Latin churches there, which served the needs of Western merchants from Venice and elsewhere.
Contrast that with the claim made at the beginning of the thread that, “suddenly in 1053 he sends off a declaration of war, then shuts up the Latin churches at Constantinople, hurls a string of wild accusations, and shows in every possible way that he wants a schism, apparently for the mere pleasure of not being in communion with the West.” It was not Cerularius who started the dispute, but rather the Normans who were attempting to force the Latin rite upon the Greeks living in Magna Graecia, nor was his act of shutting some Latin parishes down a sudden act done out of the “mere pleasure of not being in communion with the West.” In fact, it was an act done out of an effort to protect the Greeks living in Magna Graecia.
In fact, it was the legates who first hurled a string of wild accusations. Cardinal Humbert, in the bull of excommunication, accused the Greeks of treating the Latins as heretics, of rebaptizing Latins, of allowing for clerical marriage, and amusingly, for deleting the filioque from the Creed.
