When Barozzi took the bait and moved east to pursue Grillo with his much larger fleet, the latter was free to attack a Venetian convoy heading out from Venice to the Levant.
The much more manoeuvreable Genoese galleys captured or sank most of the convoy's slow-moving merchant ships, except for the giant cargo vessel (nave) Roccafortis.
The War of Saint Sabas, between the rival Italian maritime republics of Venice and Genoa, broke out in 1256, over access to, and control of, the ports and markets of the Eastern Mediterranean.
[4][5] The importance of these convoys to the Venetian economy can hardly be overstated, as described by the Italian naval historian Camillo Manfroni [it]:[6] Bales of costly wares and money were sent in it to the ports of Egypt and Asia; the dates of its departure and return were fixed by stern laws, and equally stern were the regulations as to the number of men on board each vessel; the commanders and captains were appointed by the Great Council; while in case of war the Senate pronounced the "Closing of the Sea" (Chiusura del Mare), a decree which forbade any vessel in the "caravan" from detaching itself from the main body.
If at any time there was a suspicion of foes being encountered on the high seas, the "caravan" was escorted by galleys of war, and no precaution was omitted that made for the safety of this all-important and purely commercial expedition.After the Fourth Crusade sacked Constantinople in 1204 and founded the Latin Empire on the ruins of the Byzantine state, the Venetians held a privileged position in Romania, and through that to the Black Sea, almost to the exclusion of their traditional rivals, the Genoese and the Pisans.
[8] Venetian trade in Romania had been abruptly stopped since the recapture of Constantinople and the re-establishment of the Byzantine Empire under the Palaiologos dynasty in 1261: Constantinople and the straits leading to the Black Sea were now in the hands of the Byzantine emperor, Michael VIII Palaiologos, whose alliance with the Genoese included the obligation to keep their commercial rivals away from Byzantine-held lands and preventing passage into the Black Sea.
[11][13][14] The navi in particular were of exceptional size, and their construction had been financed by public funds,[15] rather than by private contractors—usually the rich noble merchants who ran the city—as was normal practice.
This led to fears among the rival Guelph party that he might use his new position for a coup that would make him dictator on the model of the only recently deposed Captain of the People, Guglielmo Boccanegra.
He was also assigned four experienced sailors as councillors, with the added task of keeping an eye on his conduct, among them Ogerio Scoto and Pietro di Camilla.
Coupled with reports of extensive recruitment of mercenaries in Lombardy, the worried Venetian authorities delayed the sailing of the spring convoy, and prepared a large fleet of their own to counter the Genoese, with about 50 ships, mostly galleys,[b] under Andrea Barozzi (or Barocio).
At the same time, in Venice, the authorities, certain of Barozzi's eventual success given the past history of Venetian–Genoese naval encounters, and unwilling to risk losing the profits of the trade convoy, finally decided to allow it to depart on 1 August.
However, his actions up to that point show that he was already committed to an alternative plan aiming at striking the Venetian convoy, and the story of the Messinese ship may simply have been invented as a justification for deviating from the orders he had pledged to follow.
As the Genoese pressed their attack on the smaller Venetian vessels, Duaro eventually ordered their crews to abandon them and gather on the Roccafortis, bringing along what valuable goods they could carry.
[39][43] The wrath of Doge Reniero Zeno was somewhat lessened when he learned that no Venetians were made prisoners during the evacuation of the taride, and that Duaro was not well assisted by his subaltern officers.
Barozzi did not hesitate long: he not only captured the Oliva, but also began a siege of Tyre itself, in the hopes of depriving Genoa of access to the city, which at the time was the second-most important commercial entrepôt of the Levant.
[49][50] The stalemate between Venice and Genoa continued, until in 1269 King Louis IX of France, keen to use the Venetian and Genoese fleets in his planned Eighth Crusade, coerced both to conclude peace in the Treaty of Cremona.