JOHN VIII PALAIOLOGOS, Emperor of Byzantium. - Son of Manuel II Palaiologos, b. in 1383, colleague of his father on the throne, he succeeded him in 1425.
The Byzantine Empire was by now reduced to its capital alone and to a few territories in Thrace and in the Morea. G. VIII had clashed with his father's tendencies, being desirous of agreements with the Turkish sultan, and had insisted on an energetic policy. However, to resist the enormous superiority of Murad was absurd. G. VIII attempted the only path that offered hope: to find armed aid in the West with the support of the papacy. To this end he took up again the project of the union of the Churches and began negotiations with Martin V and with Eugene IV, offering the convocation of a council at Constantinople. From Rome the proposal of a council in the West was opposed.
The discussion became complicated when the conflict arose between the Roman Curia and the Council of Basel, which separately negotiated with the Byzantine Emperor. The latter hoped for an agreement with the Fathers of Basel, in order to avoid the thorny question of papal supremacy, which was objectionable to the Greeks and contested at Basel. The victory of Eugene IV and the convocation of the Council of Ferrara (18 Jan. 1438) decided G. VIII: he arrived in Italy with the Byzantine patriarch and the delegation of Greek theologians. The negotiations of Ferrara were transferred to Florence, where in 1439 the Council was moved. To facilitate the agreement, public discussions were abandoned and the question of the union was entrusted to commissions; G. VIII, anxious to save the union, imposed silence on the anti-unionists. The question of papal authority was overcome with the vague formula of the patriarch of Nicaea Bessarion. The conciliar proceedings having been closed on 5 July 1439, on the 6th the union was proclaimed in the Florentine Cathedral. G. VIII returned to his capital only in Feb. 1440, but the violent opposition of the clergy to his work prevented the union, which was not proclaimed in St. Sophia. The Emperor, urged by the Pope, sought to replace the most hostile ecclesiastical dignitaries, organized public discussions to popularize the matter, but succeeded in nothing.
The plans for a crusade discussed at Florence faded away; the attempts of John Hunyadi and of the Venetians met with indifference at Constantinople. The most serious question was now the succession to the throne: of the brothers of G. VIII, Constantine and Theodore were unionists, Demetrius on the other hand was hostile; in 1442 he had already rebelled, and in the civil war the sultan Murad intervened as peacemaker. G. VIII d. on 31 Oct. 1448.