New internal conflict - Fall of Kantakouzenos

The negotiated peace of John VI with the Genoese in 1352 at the end of the Genoese-Venetian war, prompted the Venetians to act in league with John V against the former. John V was then in Thessalonike, and felt particularly resentful at his having been removed from the throne. The Venetians and the Serbs urged him to rebel against Kantakouzenos. Negotiations with the latter were at first successful in averting a civil war, but when, in the summer of 1352, John V, backed by Venetian funds, invaded territory governed by Kantakouzenos's son, Matthew, in Adrianople, war broke out. The deceitful behaviour of John V offered John VI an excuse to depose him formally and definitively following his successful intervention in Adrianople. He ordered that his name be omitted from acclamations and, in 1354, appointed his son, Matthew, joint Emperor.

The Kantakouzenos dynasty, however, did not retain its ascendancy long. The popularity of John VI began to wane when his Turkish allies, whom, several years before, he himself had summoned from Asia Minor to assist him in his struggle, established themselves permanently on European soil. In 1352 they had already seized the fortress of Djimbi, near Kallipolis, while in March 1354, after a tremendous earthquake that drove the Byzantine inhabitants away from the area, Orhan's son, Suleiman, occcupied Kallipolis itself. In spite of Kantakouzenos' pleas, the Turks refused to leave the city. The occupation of Kallipolis caused panic among the population of Constantinople, who felt that the capital was now under serious threat. Thus, when John V, who was in Tenedos at the time, entered Constantinople with the support of the Genoese adventurer, Francesco I Gattilusio, the people went over to his side. Kantakouzenos was forced to resign and John V was left in sole possession of the throne. As for Kantakouzenos, he adopted the monk's habit and thenceforth became monk Joasaph, devoting some yearsof his life to the writing of his famous Histories. Nonetheless, he never ceased to intervene in public affairs until his death, in 1383.