Venetian – Genoese Wars The Venetian – Genoese Wars were a long - standing conflict between the Republic of Genoa and the Republic of Venice for dominance in the eastern Mediterranean Sea between 1256 and 1381 . It occurred in four spurts of open warfare . The first three were primarily naval conflicts , fought in the Eastern Mediterranean and chiefly the Aegean Sea . The first , occurring between 1257 and 1270 , demonstrated the overall superiority of Venice at sea , but could not halt the expansion of Genoese influence , especially in Byzantium . The second war , in 1294 – 1299 , was indecisive , and the third war between 1350 and 1355 was won by Genoa . The fourth , occurring between 1378 and 1381 was a victory for Venice and was fought mostly in Italy . War of 1256 – 1270 . The war broke out due to the murder of a Genoese citizen by a Venetian at Acre , whereupon the Genoese attacked the Venetian quarter . A fleet was sent from Venice in 1257 under Lorenzo Tiepolo , who defeated a larger Genoese fleet off Acre in June next year . In 1261 , Venice suffered a major setback with the signing of the Treaty of Nymphaeum between Genoa and the Nicaean emperor Michael VIII Palaiologos , as well as with the loss , soon after that , of Constantinople to a restored Byzantine Empire under Michael VIII . Throughout the war , the Venetians retained the upper hand over the Genoese in naval combat . Generally , the Genoese admirals were reluctant to confront the Venetians , even when numerically superior , and when battles took place , as in Greece at Settepozzi in 1263 and off Sicily at Trapani in 1266 , the outcome were clear Venetian victories . To protect their commerce from Genoese raids , the Venetians also instituted a successful convoy system . The only major Genoese success occurred in 1264 , when admiral Simone Grillo lured away the Venetian war fleet and destroyed the unprotected convoy . The Venetian victories also brought about the partial restoration of their position and trading rights in the Byzantine Empire , with a truce signed in 1268 . The war with Genoa was ended in 1270 through a truce mediated by Louis IX of France , who wished to embark on a crusade and needed the rival fleets for this undertaking . War of 1294 – 1299 . The long standing rivalry between Venice and Genoa broke out in the northern Aegean , Bosporus , and the Genoese colony of Galata . When Venetians attacked the colony , many of the Genoese sought shelter behind the walls of Constantinople . They in turn attacked the Venetian merchants in the city . The Venetians retaliated by attacking the suburbs outside the city walls , drawing the Byzantines into their own separate conflict . The population of Constantinople retaliated by attacking the remaining Venetians in the city . After their victory at the Battle of Curzola , the Genoese quietly withdrew from the fighting and signed the ' eternal peace ' with the Venetians in 1299 , as the war broke out to a larger Byzantine – Venetian War ( 1294 – 1302 ) . It was in this war that Marco Polo , fighting for his native Venice , was taken prisoner and while in prison wrote his memoirs . War of 1350 – 1355 . In 1348 – 1349 the Genoese fought a short war with the Byzantine Emperor John VI Kantakouzenos in Galata and Chios . In 1350 they found themselves at war with the Venetians , who sought to undermine Genoa ' s mercantile activity in the eastern Mediterranean . Genoa meanwhile had been aiding the adversaries of Aragon in Sardinia and Peter thus entered the war on the side of Venice and Byzantium . Genoa was forced into an alliance with the growing Ottoman beylik and even made an assault on Constantinople . On 16 January 1351 , a treaty was signed in Venice between the Republic and the Crown of Aragon " for the confusion , destruction , and final extermination of the Genoese . " Pope Clement VI tried to prevent fighting , but with no effect . Under their general Niccolò Pisani , the Venetians burned Galata in the early summer of 1351 and forced the emperor to join the alliance against Genoa . On 12 September the Doge of Venice , Andrea Dandolo , ratified the treaty with Aragon . The treaty specified that Aragon was responsible for disrupting Genoese activities in the western Mediterranean and Italy while Venice would take responsibility for the eastern sea and the Levant . A Genoese armada of sixty - two ships under the command of Paganino Doria sailed into the Aegean not long after the loss of Galata and besieged the Venetian fortress of Oreos on the north of Euboea , where Pisani was staying . A body of three hundred horse and a large infantry contingent was dispatched from the Duchy of Athens to hold Oreos . The siege lasted from 15 August until 20 October 1351 , when Doria was forced to lift the siege by the arrival of a Catalan fleet led by Pons de Catapan and the assistance the garrison received from Venice . Pteleum was ravaged and looted and the entire archipelago suffered a spate of Genoese piracy . In January 1352 , Venice drew the Republic of Pisa into the war on her side against Genoa , which had defeated the Pisans at the Battle of Meloria three generations earlier , putting an end to their power in the Mediterranean . On 13 February , a Venetian - Aragonese fleet met the Genoese near Constantinople in the indecisive Battle of the Bosporus ; both sides suffered heavy losses , but in the end Venice had to abandon the Bosporus and the Aragonese fleet was hardest hit . On 6 May , the emperor had no choice but to come to terms of peace with Paganino Doria . Venice responded by paying his son - in - law , John V Palaiologos , to enter the war against him and the Genoese . John VI then began a campaign for papal support and the union of the Catholic and Orthodox churches . Pope Innocent VI responded with enthusiastic support for the Byzantine emperor in a letter of 15 March 1353 and in another of 29 September , addressed to Genoa , urged the city - state to make peace with Venice and Aragon . The pope ' s enthusiasm quickly abated as John Palaiologos entered Constantinople the next year ( 1354 ) . On 29 August 1354 , the Genoese were defeated at Alghero on Sardinia and forced to submit to Giovanni Visconti , Lord of Milan , who then financed a fleet with which to send Doria back to the east , where he defeated Venice and captured thirty five galleys at Zonklon . This last defeat was a factor in the deposition of doge Marino Faliero . Venice made peace with Genoa on 1 June 1355 . War of 1378 – 1381 . In 1378 open fighting broke out again between Venice and Genoa over possession of the Greek island of Tenedos . It is generally called the " War of Chioggia " after the battle which was fought there in 1381 . This conflict saw the first use of shipborne cannons in support of amphibious assault operations , and perhaps against Genoese galleys . The conflict was nearly disastrous for both sides , and Genoa was certainly crippled . Venice might have suffered as badly , were it not for its admirals Vettor Pisani and Carlo Zeno . In 1379 , the Genoese defeated the Venetians off Pula , but the Venetians trapped them in the lagoons of Chioggia and destroyed their fleet in 1380 in the Battle of Chioggia . Through the mediation of the " Green Count " of Savoy , Amadeus VI , the two sides made a peace treaty at Turin which , due to Genoa ' s ruin , was to last a good time .