Uzun Hassan had already been in collision with the Turks, having, when ruler of Diarbekr, undertaken to defend Calo Johannes of the noble house of the Comneni, one of the last of the Christian emperors of Trebizond, against Mahomet II. This alliance had been cemented by his marriage with the beautiful princess Despina, daughter of Calo Johannes, in which manner he was connected with some of the princely families of Venice, so that the way for an embassy was easily paved. The Venetians might hope much from the ambitious and turbulent character of the Persian prince; and in this they were not disappointed, as it needed but little persuasion to induce the hitherto almost invincible soldier to take up arms against his hereditary foe. Worn out by a state of anarchy, rival chiefs and tribes struggling for power before the land had fully risen again after the blast of foreign conquest had passed over it, the ancient glory of Persia had paled before the brighter light of its rival; but the old hatred still remained, with the will, if not the power, to oppose the Turkish arms. An embassy to Uzun Hassan being determined on, the difficult task of sending an envoy still remained. The duty would be a hazardous one, as any one proceeding from Venice to Persia would have to run the gauntlet of the Turks. The sister of Queen Despina had married Nicolo Crespo, the Duke of the Archipelago, whose four daughters were in turn wedded to four of the merchant princes of Venice, one of whom was M. Caterino Zeno, a man of courage and talent. He, of all others, appeared the fittest to undertake this honourable but perilous mission, and the patriotism of Zeno induced him to overlook the dangers he would run in traversing hostile and almost unknown regions before reaching his destination. He was rewarded for his courage by arriving safely in the presence of the king, though not without meeting serious obstacles in his journey through Caramania. Zeno was well received by the monarch; and, being supported in his arguments by his aunt, the Queen Despina, succeeded in inducing Uzun Hassan to take up arms against the Turk. In 1472 the Persians marched into the Turkish dominions and ravaged them, but a flying column under Mustafà, the second son of Mahomet II, routed a force of Persians under one of Uzun Hassan’s generals. In the following year the Grand Turk invaded Persia with an immense army, but met with a severe check while endeavouring to cross the Euphrates near Malatia, and was forced to retreat. Uzun Hassan, however, following up his success too rashly, was routed by the Turks at Tabeada. M. Caterino Zeno was then sent as ambassador from Uzun Hassan to various Christian princes, among others to Poland and Hungary, to incite them to take up arms against the Ottoman. M. Josafat Barbaro and Ambrogio Contarini were sent from Venice to take his place at the Persian Court; but no arguments could again induce the Persian monarch to meet the Turks in the field.