David had played an important role throughout the reign of his older brother and predecessor
John IV. He had been given the courtly title of
despotes, which in Trebizond designated the heir to the throne. David had participated in his brother's expeditions against the
Genoese, and also fulfilled various diplomatic tasks. In 1458 he ratified his brother's treaty with the
Ottoman Sultan
Mehmed II in
Adrianople, and later the same year he conveyed his niece Theodora to her husband,
Uzun Hassan of the
Ak Koyunlu. David ascended the throne shortly after his brother's death, sometime in April 1460. Although John IV had made his nephew
Alexios V his heir, Alexios was a minor; according to
Laonikos Chalkokondyles David, with the support of the Kabasitanoi
archontes, pushed the young emperor aside and took the throne for himself. With the conquest of
Constantinople by the
Ottoman Turks in 1453, the threat Mehmet II posed to the pocket empire had increased. David's brother John had spent the following years up to his death building alliances to protect the empire, with the
Georgian princes to the east and with Uzun Hassan of the Ak Koyunlu, and David seems to have counted on their support. The Muslim rulers of
Sinope and
Karaman appear to have been enlisted as allies by John or Uzun Hassan. About this time, October 1460, one
Ludovico da Bologna appeared at the court of Emperor
Frederick III with two men who were ostensibly the ambassadors of Persia and Georgia; more specifically, the Persian ambassador—Nicholas of Tbilisi—was the representative of
George VIII of Georgia, and the Georgian ambassador—recorded as "Custopa", "Custoda", "Chastodina" and other variations—represented
Qvarqvare II, prince of
Samtskhe. They carried letters signed not only by those Eastern rulers, but four more, as well as three Caucasian tribes all eager to take part in an alliance against the Ottomans. Ludovico's entourage proceeded to
Venice, and either there or at their next stop, Florence, a new ambassador joined his following: Michael Alighieri, who said he was the envoy of Emperor David. In Florence, a city that was eager to build up a network of bases in the Levant, Alighieri negotiated a treaty between Florence and David of Trebizond granting to the city a consulate (
fondaco) and trading terms that included a 2% levy on exports, as were enjoyed by the Genoese and Venetians in Trebizond. Like his ancestor,
Dante Alighieri, Michael Alighieri was a Florentine, but had been trading on his own account in the Black Sea. Bryer mentions a document dated 28 April 1470, wherein the protectors of the Bank of St. George at Caffa gave Michael Alighieri safe conduct which covered his children and subordinates. Bryer treats Ludovico da Bologna's claims with a degree of distrust and suspicion, noting Ludovico "seems to have been too glib and later obsessed with something of the attitude of a
Baron Corvo towards the Church, which failed to take his personal ambitions seriously." On the other hand, Bryer assumes Michael Alighieri was a legitimate representative of Emperor David, although the letter he bore from David to Duke
Philip the Good of
Burgundy "was written, if not in Italy, from an Italian point of view, and by someone who knew Trebizond well and had recently seen David Komnenos as the new Emperor." William Miller, in his account of the Empire of Trebizond, likewise assumes Michael Alighieri was the legitimate representative, while ignoring the existence of the sketchy Ludovico da Bologna, who had been the primary advocate for a Christian league. With Western support against the Ottomans still unsolidified, David prematurely asked the Sultan for a remission of the tribute paid by his predecessor. Even worse, he made these demands through the envoys of Uzun Hassan, who made even more arrogant demands on behalf of their master. Sultan Mehmed dismissed them, telling them that they would know his answer later. That answer came the summer of the next year: a fleet under his admiral
Kasim Pasha sailed along the Black Sea coast of
Anatolia towards Trebizond while he led an army from
Bursa eastwards towards the city. == The fall of Trebizond ==