Second Council of Lyon

[1] Pope Gregory X presided over the council, called to act on a pledge by Byzantine emperor Michael VIII to reunite the Eastern church with the West.

Due to the great number of attendees, those who had come to Lyon without being specifically summoned were given "leave to depart with the blessing of God" and of the Pope.

In the second session, the fathers approved the decree Zelus fidei, which contained no juridical statutes but rather summed up constitutions about the perils of the Holy Land, the means for paying for a proposed crusade, the excommunication of pirates and corsairs and those who protected them or traded with them, a declaration of peace among Christians, a grant of an indulgence for those willing to go on crusade, restoration of communion with the Greeks, and the definition of the order and procedure to be observed in the council.

[2] Wishing to end the Great Schism that divided the Catholic Church from Eastern Orthodoxy, Pope Gregory X sent an embassy to Michael VIII, who had reconquered Constantinople, putting an end to the remnants of the Latin Empire in the East, and he asked Latin despots in the East to curb their ambitions.

His son and successor Andronicus II repudiated the union in the Council of Blachernae (1285), and Bekkos was forced to abdicate, being eventually exiled and imprisoned under house arrest until his death in 1297.

The council drew up plans for a crusade (passagium generale) to recover the Holy Land, which was to be financed by a tithe imposed for six years on all the benefices of Christendom.

[13] Abaqa's Latin secretary Rychaldus delivered a report to the council, which outlined previous European-Ilkhanid relations under Abaqa's father, Hulagu, where after welcoming the Christian ambassadors to his court, Hulagu had agreed to exempt Latin Christians from taxes and charges, in exchange for their prayers for the Qaghan.

This text puts forward four main decisions to accomplish the Crusade: the imposition of a new tax during three years, the interdiction of any kind of trade with the Saracens, the supply of ships by the Italian maritime Republics, and the alliance of the West with Byzantium and the Il-Khan Abagha.

[17] However, despite papal plans, there was little support from European monarchs, who at this point were more likely to give lip service to the idea of a Crusade than to commit actual troops.

There had been several lengthy vacancies of the Holy See, most recently the sede vacante that had lasted from the death of Clement IV, 29 November 1268, until Gregory's election, 1 September 1271.