[2] This civil war depleted Byzantium's scarce resources and greatly facilitated the Ottoman conquest of the Balkans, most notably through the cession of Gallipoli by Andronikos.

As a result, he proposed to cede to the Venetians the island of Tenedos, strategically located at the entrance of the Dardanelles, in exchange for further funds and six warships.

The Venetians accepted, but when news reached Constantinople, Andronikos IV, likely urged by the Genoese, Venice's commercial rivals, refused to honour his father's agreement.

This left John stranded in Venice, effectively as a captive debtor of the Republic; when he suggested that funds be raised to secure his release by selling precious objects from the churches, Andronikos again refused, claiming that this was impious.

On 6 May, Andronikos IV fled Constantinople and allied with Murad's son Savcı Bey, who was rebelling against his own father.

Gallipoli had been retaken by the Byzantines ten years before, with the assistance of Amadeus VI, Count of Savoy; this strategically important bridgehead greatly improved the sultan's ability to attack Europe.