Dušan, now that has conquered Epirus and Thessaly, seeks to obtain Constantinople.

To acquire the city, he needs a fleet.

Knowing that fleets of southern Serbian Dalmatian towns are not strong enough to overcome Constantinople, he opens negotiations with Venice, with which he maintains fairly good relations.

Venice fears a reduction of privileges in the Empire if Serbs become the masters of Constantinople over the weakened Greeks, but if the Venetians had allied with Serbia, Dushan would have examined existing privileges.

Once he became master of all imperial lands (especially Thessalonika and Constantinople) the Venetians would gain privileges.

Venice chooses to avoid a military alliance.

While Dušan seeks Venetian aid against the Empire, the Venetians seek Serbian support in the struggle against the Hungarians over Dalmatia.

When sensing that Serbian aid would result in a Venetian obligation to Serbia, Venice politely turns down Dušan’s offers of help.