The second civil war
The second civil war was consequently even more destructive of property and ruinous to the economy than the first. At the same time, in 1347, the Black Death decimated the population of Constantinople and other parts of the empire. John VI Cantacuzenus, nevertheless, did what he could to restore the economy and stability of the empire. To coordinate the scattered fragments of its territory he assigned them as appanages to individual members of the imperial family.
His son Manuel took over the province of the Morea in 1349 with the rank of despot and governed it with growing success until his death in 1380; his eldest son, Matthew, was given a principality in Thrace; while the junior emperor John V, who had married a daughter of Cantacuzenus, ruled in Thessalonica after 1351.
Cantacuzenus also tried but failed to weaken the economic stranglehold of the Genoese by rebuilding a Byzantine war fleet and merchant navy. The effort involved him in warfare, first on his own and then as an unwilling partner of the Venetians against the Genoese, from which Byzantium emerged as the loser. The revenue of the Genoese colony at Galata, derived from custom dues, was now far greater than that of Constantinople.
The empire’s poverty was reflected in dilapidated buildings and falling standards of luxury. The crown jewels had been pawned to Venice during the civil war, and the Byzantine gold coin, hopelessly devalued, had given place in international trade to the Venetian ducat. More and more, Byzantium was at the mercy of its foreign competitors and enemies, who promoted and exploited the political and family rivalries among the ruling class.
John Cantacuzenus was never popular as an emperor, and feeling against him came to a head when some of his Ottoman mercenaries took the occasion of the destruction of Gallipoli by earthquake to occupy and fortify the city in March 1354. It was their first permanent establishment in Europe, at the key point of the crossing from Asia. In November of the same year John V Palaeologus, encouraged by the Anti-Cantacuzenist Party, forced his way into Constantinople. In December Cantacuzenus abdicated and became a monk. Though his son Matthew, who had by then been crowned as coemperor, fought on for a few years, the dynasty of Cantacuzenus was not perpetuated.