| Byzantine–Venetian treaty of 1277 | |
| Type: | Two-year non-aggression pact and commercial treaty |
| Date Signed: | 19 March 1277 |
| Location Signed: | Constantinople |
| Signatories: |
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The Byzantine–Venetian treaty of 1277 was an agreement between the Byzantine Empire and the Republic of Venice that renegotiated and extended for two years the previous 1268 treaty between the two powers. The agreement was beneficial for both sides: Byzantine emperor Michael VIII Palaiologos kept the Venetians and their fleet from participating in the attempts of Charles of Anjou to organize an anti-Byzantine crusade, while the Venetians were able to retain their access to the Byzantine market, and even augment their trading privileges by gaining direct access to the Black Sea and the right to their own quarters in Constantinople and Thessalonica. Furthermore, they were able to stop the Byzantine reconquest of Venetian-aligned territories in the Aegean, although the treaty explicitly allowed both sides to continue fighting for control of the island of Euboea (Negroponte). Nevertheless, the agreement's short duration made clear that for both parties, it was a temporary expedient. After the treaty expired, the Venetians allied with Charles of Anjou, but their plans were thwarted by the outbreak of the War of the Sicilian Vespers in 1282, forcing Venice once more to renew the peace with the Byzantines in 1285.
The reconquest of Constantinople by the Nicaean emperor Michael VIII Palaiologos in 1261, and the re-establishment of the Byzantine Empire under the Palaiologos dynasty, was a major blow to the position and commercial interests of the Republic of Venice in the Eastern Mediterranean. To safeguard himself against the mighty Venetian fleet, Palaiologos had also allied with the Republic of Genoa, which was at war with Venice, in the Treaty of Nymphaeum. However, the Genoese defeats in the war against Venice, along with the gradual consolidation of Palaiologos' own position, led to a widening rift between the two allies. In 1264, when the Genoese Italian: [[podestà]] in Constantinople was implicated in a plot to surrender the city to Manfred of Sicily, the Emperor expelled the Genoese from the Byzantine capital.
In the aftermath, Palaiologos began negotiations with Venice for a peace treaty. A draft agreement was reached on 18 June 1265, but it was not ratified by the Doge of Venice. With the rise of the ambitious Charles of Anjou in Italy, both Palaiologos and the Venetians became interested in a mutual rapprochement, leading finally to the conclusion of a five-year peace treaty in 1268. Reflecting the improved negotiating position of the Byzantine emperor, its terms were more advantageous to him than the 1265 treaty. The truce originally expired in 1273, but it is clear from the wording of the 1277 treaty that it had continued being in force for some time afterward as well. It is unknown whether that was due to an annual extension—possibly repeated—of the treaty, or a complete new treaty that has not survived.
The treaty's provisions regarding the free and safe movement of Venetian merchants and their goods were not scrupulously observed by the Byzantines, leading to vociferous protests by the Venetians: in 1278, the Doge submitted more than 300 cases of injury done to Venetian ships, merchants, and goods since 1268, at the hands of the Emperor's subjects; many of them pirates in Imperial employ, but also including soldiers, customs officials and local governors, and even, on one occasion, a (possibly Palaiologos' half-brother Constantine), who had robbed and murdered a Venetian archdeacon captured on a ship off the Morea. Nevertheless, following the Union of the Churches at the Second Council of Lyon in 1274, Palaiologos was at a strong position: the Popes now recognized him as a legitimate ruler, blocked Charles of Anjou's plans to attack Constantinople, and tried to recruit the Byzantines into their plans for a Crusade to recover the Holy Land. At the same time, the Byzantines had been making headway against the various Latin principalities established in the Aegean in the aftermath of the Fourth Crusade. Headed by the Latin renegade Licario, the Byzantine fleet recovered most of the smaller Aegean islands, and much of the large island of Negroponte (Euboea), apart from its capital, the city of Negroponte (Chalkis), which was defended by a Venetian Italian: [[Bailo of Negroponte|bailo]].
Dismayed at the Byzantine advances, and by the threat posed to Venetian commerce by the corsairs funded by Palaiologos, the Venetians sent envoys to Constantinople to renew the 1268 treaty. A Venetian embassy under Marino Valaresso, Marco Giustinian, and Angelo Marcello had been at the Byzantine court already in 1275. Walter Norden (Das Papsttum und Byzanz, 1903) speculated that a treaty was signed already in that year, but there is no evidence for that in the sources. Events were helped along by the death of the recalcitrant Doge Lorenzo Tiepolo, who resisted any concessions to Palaiologos, and his succession by Jacopo Contarini. The Venetians were also worried by the renewal of a Byzantine treaty with the Genoese, which guaranteed their possession of Galata across the Golden Horn from Constantinople, giving the Genoese an advantage in trade with the Empire.
On 2 September 1276, the Venetian ambassadors, Marco Bembo and Matteo Gradenigo, received authority to conduct negotiations and conclude an agreement. Contarini was careful to avoid terms that might give offense to Palaiologos, omitting the title 'Lord of one-quarter and one-eighth of the Empire of Romania' that his predecessors had claimed since the Fourth Crusade, and limiting himself to the title of 'Doge of Venice, Dalmatia, and Croatia, and lord of the places and islands subject to his Dogate' (Latin: Venecie, Dalmacie et Croacie Dux, dominus terrarum et insularum suo Ducatui subiectarum). Likewise, the Doge was careful to address Palaiologos as 'Emperor of the Romans' (Latin: Imperator et moderator Romeorum) and 'the New Constantine' (Latin: novus Constantinus). Gradenigo died during the long negotiations, and the agreement was finally concluded by Bembo alone on 19 March 1277. Notably, this agreement was not phrased as a treaty between equals, but rather as a chrysobull, a deed of grant, from the Emperor, "desirous of keeping the peace with all Christians", to Venice.
The Latin text of the treaty is published in the collection of Venetian documents by Tafel and Thomas, and its Greek text by Miklosich and Müller. The clauses of the treaty were:
It is clear that both sides were cautious, hedging their bets in view of the volatile international situation, as seen by the treaty's short duration. Venice in particular still hoped for the realization of a crusade against Palaiologos, that might lead to the restoration of Venetian domination as it had existed before 1261.
As a result, the treaty was not renewed after its expiration, and in 1281, the Venetians in the Treaty of Orvieto entered Charles of Anjou's anti-Byzantine coalition, with April 1283 as the projected starting date for the expedition against Constantinople. However, Charles' designs were fatally interrupted by the outbreak of the Sicilian Vespers in March 1282 and the consequent War of the Sicilian Vespers. By the terms of the Treaty of Orvieto, a state of war existed between Venice and Byzantium. The outbreak of the Vespers had ruined Venetian chances to recover their privileged position, and for the duration of the state of war their trade with the East was interrupted, much to the advantage of the Genoese. After long negotiations, a ten-year peace treaty, essentially renewing the 1277 agreement, was concluded in July 1285.
The compensation clause included in the treaty has been the subject of some debate among modern scholars: according to the terms, the mechanism for compensation was to be 'in accordance with the form of the first truce', but there is nothing in the 1268 treaty to this effect. Such a clause may have been inserted, however, in any renewal or renegotiation of the treaty after 1273. In accordance to this clause, the Venetian government set up a three-member commission to examine the claims of Venetian merchants for losses incurred by Imperial agents during the truce. The commissioners, Giberto Dandolo, Marino Gradenigo, and Lorenzo Sagredo, examined 339 claims on 257 incidents, consulting official dispatches by Venetian agents in the Aegean as well as oral evidence from individuals, and issued their report in March 1278. The Venetian claims totalled about 35,000, but it was not until the 1285 treaty that the Venetian claims were recognized by the Byzantine Emperor Andronikos II Palaiologos, who agreed to pay out 24,000 in compensation.