JOHN VIII PALAEOLOGUS, EMPEROR OF BYZANTIUM. – Son of Manuel II Palaeologus, born in 1383, he was associated with his father on the throne and succeeded him in 1425.
The Byzantine Empire was now reduced to the capital alone and a few territories in Thrace and the Morea. John VIII had opposed his father’s tendencies, which favoured agreements with the Turkish sultan, and had insisted on a vigorous policy. Yet resistance to the overwhelming superiority of Murad was futile. John VIII pursued the only path offering hope: securing military aid from the West with papal support. To this end, he revived the project of Church union and opened negotiations with Martin V and Eugene IV, offering to summon a council in Constantinople. From Rome came the counter-proposal of a council in the West.
The discussion grew more complicated when the Roman Curia and the Council of Basel separately negotiated with the Byzantine emperor. He hoped to reach an agreement with the Fathers of Basel to sidestep the thorny issue of papal supremacy, which was repugnant to the Greeks and contested at Basel. The victory of Eugene IV and the transfer of the Council to Ferrara (18 January 1438) decided John VIII: he arrived in Italy with the Byzantine patriarch and a delegation of Greek theologians. The negotiations moved to Florence, where the council reconvened in 1439. To facilitate agreement, public debates were abandoned, and the question of union was entrusted to commissions; John VIII, anxious to secure the union, silenced the anti-unionists. The question of papal authority was circumvented by the vague formula of Bessarion, patriarch of Nicaea. The council concluded its work on 5 July 1439, and on the 6th the union was proclaimed in Florence Cathedral. John VIII returned alone to his capital in February 1440, but violent opposition from the clergy prevented the union from being proclaimed in Hagia Sophia. Urged on by the Pope, he attempted to replace the most hostile ecclesiastical dignitaries and organised public debates to popularise the union, but to no avail.
The crusade plans discussed in Florence came to nothing; the efforts of John Hunyadi and the Venetians met with indifference in Constantinople. The gravest issue now was the succession to the throne: of John VIII’s brothers, Constantine and Theodore were unionists, while Demetrius was hostile; in 1442 Demetrius had already rebelled, and in the civil war the sultan Murad intervened as a peacemaker. John VIII died on 31 October 1448.