The Second Council of Lyons
In the early 1270s the Byzantines were threatened by the Serbs, the Bulgarians, and especially the Latin state of Achaia, in Greece, led by the Sicilian Norman, Charles of Anjou. And the Seljuk Turks, who had occupied most of Asia Minor in the previous two centuries, were an ongoing threat. In response to these pressures, Emperor Michael VIII appealed for support to Pope Gregory X (r. 1271–1276), who opposed Charles’ designs on Constantinople. Michael suggested that in return for military assistance, the Greek Church would accept the authority of the Papacy.
The reunion of the Eastern and Western Churches, therefore, was the major issue discussed at the Second Council of Lyons, which met in 1274 at Pope Gregory’s request. The Greek delegation brought letters accepting Papal authority and various Roman Catholic articles of faith, including the filioque clause in the Nicene Creed. It was at this council that for the first time the Western Church proclaimed that the filioque must be accepted as dogma. The Union agreement that restored communion between the two Churches stipulated that the Greeks could retain their liturgical rites and customs. The council also attempted to launch another Crusade to the Holy Land, and it established the practice of all the Roman cardinals meeting in a closed conclave during the entire process of electing a new pope.
When Emperor Michael VIII attempted to impose the so-called Union of Lyons upon the Byzantine Church, it was met with great resistance. When Patriarch Joseph of Constantinople refused to sign the agreement, he was deposed and replaced with John Beccus, who was the head of the minority party in Constantinople that favored the Union. But after Michael died in 1282, Beccus was quickly deposed, Joseph was restored to the patriarchal throne, and the Union of Lyons was officially renounced. Popular opposition to Emperor Michael was so strong that he was denied a church burial.
Remarkably, Michael retained his loyalty to the Union of Lyons even though in 1281 the new Pope Martin IV (r. 1281–1285) excommunicated him as part of the Pope’s plan to assist Charles of Anjou, one of his major supporters, in attacking and conquering the Byzantine Empire. But that plan, and the Council of Lyons’ plan to launch a new Crusade to the Holy Land, both came to naught.