Tunis did not long remain in the possession of Barbarossa. The banished king appealed to Charles V., and, whatever the emperor may have thought of Hasan's wrongs, he plainly perceived that Barbarossa's presence in Tunis harbour was a standing menace to his own kingdom of Sicily. It was bad enough to see nests of pirates perched upon the rocks of the Algerine coast; but Tunis was the key of the passage from the west to the eastern basin of the Mediterranean, and to leave it in the Corsairs' hands was to the last degree hazardous. Accordingly he espoused the cause of Hasan, and at the end of May, 1535, he set sail from Barcelona with six hundred ships commanded by Doria (who had his own grudge to settle), and carrying the flower of the Imperial troops, Spaniards, Italians, and Germans. In June he laid siege to the Goletta--or _halk-el-wēd_, "throat of the torrent," as the Arabs called it--those twin towers a mile asunder which guarded the channel of Tunis. The great carack _St. Ann_, sent, with four galleys, by "the Religion" (so the Knights of Malta styled their Order), was moored close in, and her heavy cannon soon made a breach, through which the Chevalier Cossier led the Knights of St. John, who always claimed the post of danger, into the fortress, and planted the banner of "the Religion" on the battlements[30] (14 July). Three desperate sallies had the besieged made under the leadership of Sinān the Jew; three Italian generals of rank had fallen in the melley; before they were driven in confusion back upon the city of Tunis, leaving the Goletta with all its stores of weapons and ammunition, and its forty guns, some of them famous for their practice at the siege of Rhodes, and more than a hundred vessels, in the hands of the enemy. Barbarossa came out to meet the emperor at the head of nearly ten thousand troops; but his Berbers refused to fight, the thousands of Christian slaves in the Kasaba (or citadel), aided by treachery, broke their chains and shut the gates behind him; and, after defending his rampart as long as he could, the Corsair chief, with Sinān and Aydīn "Drub-Devil," made his way to Bona, where he had fortunately left fifteen of his ships. The lines of Kheyr-ed-dīn's triple wall may still be traced across the neck of land which separates the lake of Tunis from the Mediterranean. Fifteen years ago this rampart was cut through, when nearly two hundred skeletons, some Spanish money, cannon balls, and broken weapons were found outside it.[31]