The year 1354 was the point of no return for the Byzantine Empire. In that year the Ottoman Turks put down their roots on European soil at Gallipoli. In that year John Cantacuzene, who had tried to contain the enmity of the Turks and to loosen the stranglehold of the Italians, was forced to abdicate. His policies had failed. The Venetians no less than the Genoese opposed his efforts to reconstitute a Byzantine fleet. They had too much to lose. Andrea Dandolo, who died in 1354, had faithfully recorded his view of the changing nature of the relationship between Byzantium and Venice. From being a province of Byzantium, Venice had graduated to being a protectorate, an ally and a partner. By the time of Dandolo's death Byzantium had long ceased to be the senior partner in the relationship. It was scarcely a partnership at all. Neither could live without it. But the profit and the honour went all to Venice. It was to uphold these two principles that the Venetians went to war with Genoa and browbeat the Byzantine Emperors into regular renewals of the commercial privileges on which their profits depended.

Dandolo had lived to see the colonial empire of Venice, the empire within an empire, firmly established. Before the Fourth Crusade the Venetian quarter in Constantinople and the trading stations in the Byzantine world had led a precarious existence, dependent on the goodwill of the emperors, the good behaviour of their inhabitants and the caprice of the Greeks among whom they lived.