In 1537, two years after the fall of Tunis, the Sultan declared war on Venice. The Turkish fleet, although led by the Sultan Soliman himself, was defeated by the Venetians off Corfu. Doria, in the service of Charles V, caught and burned ten richly laden Turkish merchant ships and then defeated a Turkish squadron. The prestige of the Crescent on the sea was badly weakened by these events, but suddenly Barbarossa appeared and raided the islands of the Archipelago and the coasts of the Adriatic with a savagery and sweep unmatched by anything in his long career. He arrived in the Golden Horn laden with booty, and delivered to his master, the Sultan, 18,000 captives. This exploit changed the complexion of affairs. During the winter of 1537-1538 the naval yards of Constantinople were busy with the preparations for a new fleet which should take the offensive against the Venetians and the Christians generally. In the spring Barbarossa got out into the Archipelago and, raiding at will, swept up another batch of prisoners to serve as galley slaves for the new ships. Meanwhile the Mediterranean states nerved themselves for a final effort. Venice contributed 81 galleys, the Pope sent 36, and Spain, 30. Later the Emperor sent 50 transports with 10,000 soldiers, and 49 galleys, together with a number of large sailing ships. Venice also added 14 sailing ships of war, or "nefs," and Doria 22; these formed a special squadron. The Venetian nefs were headed by Condalmiero in his flagship the _Galleon of Venice_, the most formidable warship in the Mediterranean, and the precursor of a revolution in naval architecture and naval tactics. [Illustration: 16TH CENTURY GALLEY]