Relations with Genoa - Genoese-Venetian war

uring the first years of the reign of John VI Kantakouzenos, the Byzantine Empire consisted of Constantinople, Philadelphia in Asia Minor, the Byzantine possessions in the Morea, Thrace, a few islands in the Aegean Sea, a handful of cities along the coast of Asia Minor, and Thessalonike. To maintain control over these areas, but also to release the Empire from its financial dependence on the Italian maritime republics, in particular that of Genoa, which was the dominant commercial power in the Byzantine seas and had furthermore wrested Chios from the Byzantines in 1346, John VI took two measures. First, he proceeded to build up a fleet and second, he reduced the customs duty on ships entering the port of Constantinople.

However, these measures of Kantakouzenos' and especially his ship-building programme seemed dangerous to the Genoese, who feared they might thus lose their privileges. As a result, a war broke out between the Genoese and the Byzantines, which ended in the defeat of the latter in 1349. Despite this defeat, the Byzantines became involved shortly afterwards in the Genoese-Venetian war over the commercial control of the Black Sea (1351). Although reluctant at first, John VI finally sided with Venice, which was also suppported by Peter, King of Aragon. The naval battle that took place on 13 February 1352 was indecisive and led to the conclusion of peace between the Venetians and the Genoese. Following this, the Venetians and the Aragonese withdrew, leaving Kantakouzenos alone. Abandoned by his allies, he was forced to negotiate peace with the Genoese in May 1352. The intervention of John VI in the Genoese-Venetian war not only resulted in more losses and defeats for the Byzantines, but also gave rise to new conflicts between the elder Emperor and his younger co-Emperor, John V.