The Byzantine–Genoese War of 1348–1349 was a military conflict between the Byzantine Empire and the Republic of Genoa, fought primarily over control of custom dues collected from maritime trade passing through the Bosphorus Strait.
Background
Following the Treaty of Nymphaeum of 1261, the Genoese held the colony of Galata, a fortified suburb of Constantinople located across the Golden Horn. This treaty granted Genoa extensive trade privileges within the empire, including the right to collect customs dues at Galata. By the mid-14th century, Constantinople collected only about thirteen percent of all custom dues from shipping through the Bosphorus—approximately 30,000 hyperpyra annually—with the remainder going to Genoa. The Byzantine Empire was severely weakened by the civil war of 1341–1347, during which the Byzantine navy was completely destroyed. Thrace, the empire's main territorial possession besides the Despotate of the Morea, was still recovering from devastation caused by marauding Turkish mercenaries during the civil war.
Conflict
Emperor John VI Kantakouzenos sought to regain control of the custom duties by lowering Constantinople's tariffs to undercut the Genoese in Galata. With an empty treasury, he raised 50,000 hyperpyra in private loans to rapidly build a new fleet. When the reduced tariffs diverted merchant shipping away from Galata to Byzantine Constantinople, the Genoese responded by fortifying Galata in violation of their treaty with Byzantium.
The Genoese declared war in August 1348. A Genoese flotilla sailed across the Golden Horn and attacked the Byzantine fleet; despite extensive preparations, the Byzantine fleet was destroyed by early 1349. The Byzantines retaliated by burning wharves and warehouses along the shore and using catapults to hurl stones and burning bales of hay into Galata, setting large parts of the city on fire. After several weeks of fighting, plenipotentiaries from Genoa negotiated a peace agreement. The Genoese agreed to pay a war indemnity of 100,000 hyperpyra, evacuated land behind Galata that they had illegally occupied, and promised never to attack Constantinople. The Byzantines surrendered nothing, but the Genoese retained their control over custom duties.
Aftermath
Historians differ on the outcome of the war. George Ostrogorsky states that the Byzantines lost the conflict, while John Julius Norwich argues that they won. The failure of the Byzantines to expel the Genoese from Galata meant that they could never restore their naval power and would thereafter depend on either Genoa or Venice for naval aid. From 1350, the Byzantines allied with the Republic of Venice, which was also at war with Genoa. However, as Galata remained defiant, the Byzantines were forced to settle the conflict in a compromise peace in May 1352.
