At the time that he summoned Manuel to deliver Constantinople, Bayezid fortified the gulf of Nicomedia, and built at Scutari the castle called Guzel Hissar.[585] About the same time, the castle of Anatoli Hissar was built at the mouth of the Sweet Waters of Asia, the narrowest point on the Bosphorus. When Clavijo passed through the Bosphorus, in 1403, he spoke of this castle as strongly built and strongly fortified, in prophetic contrast to the ruined Byzantine fortress directly opposite on the European shore.[586] Perhaps it was because of the advice of Ali Pasha, who told him that the taking of Constantinople would bring upon him a really effective European intervention, or because he preferred to expend his energies in the Greek peninsula and in Asia Minor, that Bayezid did not carry out his threat to Manuel. These are the common explanations of the failure to follow up the victory of Nicopolis with the extinction of the Byzantine Empire.[587] As far as the Greeks were concerned, the inheritance of the Caesars was his. He had successfully defended against Europe what he had won. Constantinople could have been taken by assault. In fact, from his spies within the city, Bayezid knew that the inhabitants were favourable to surrender, and would probably force the hand of Manuel, if the Osmanlis made a show of beginning the assault. Bayezid must have been deterred from this enterprise, however, by the realization of his inability to hold the city without having the mastery of the sea. One of Bayezid’s chief claims to greatness as a statesman is the way in which he handled Venice and Genoa. At any time during his reign, the Italian republics could have cut him off from Asia if he were in Europe, or from Europe if he were in Asia. Bayezid was master of most of the Balkan peninsula and of half of Anatolia; but he did not control the path from one portion of his empire to the other. Since he had come to the throne, Genoa had fallen under the influence of France. There was a strong anti-Ottoman sentiment in the Venetian Senate, which at any instant might crystallize into open hostility.[588] Europe was for the moment stirred over the fate of the Nicopolis crusaders. Bayezid knew that this was not the time to take Constantinople. Then, too, after the great victories of Kossova and Nicopolis, and his successful campaign against Karamania, Bayezid allowed himself to succumb to the insidious temptations that assail the warrior when he passes from the tent to the palace. It was not astonishing that the pleasures of the table and of the harem proved irresistible to him. Bayezid, who had the best qualities of his age, allowed himself to become debauched by indulgence in shameful and unspeakable vices. His brilliant mental and physical qualities began to suffer the inevitable eclipse. His example was contagious. For, as the Osmanlis say, ‘the fish begins to corrupt at the head’. XIII