His first care was to fortify the city of Algiers, and he expended a great deal of money and labor on the perfection of the harbor, compelling all his prisoners and thousands of citizens to work as slaves on the defenses. Next he conquered Tunis, and was selected by the sultan as the only fit man to sail against Andrea Doria, the great Genoese naval commander of the Christians in their wars against the Turks early in the sixteenth century. Mediterranean commerce became so unsafe that watch-towers were built all along the coasts, and guards were kept afoot to give alarm at the approach of the corsairs. Charles V gathered together a powerful armament, and sailed to the rescue of Tunis, recapturing it for its rightful sovereign in 1535; but he was never able to capture Hayradin Barbarossa, who lived out his life in Algiers as “a friend to the sea and an enemy to all who sailed upon it.” After his time the power of the pirates continued under other leaders; and not Algeria alone, but Tripoli, Morocco, and even Tunis, harbored piratical vessels in every port, and the rulers shared their spoils; piracy, indeed, was the source of their national revenues, and was encouraged by the Sultan of Turkey inasmuch as all these states were his vassals. Every few years some European power—Spain, France, Venice, or England—would lose patience, send a fleet, and open a campaign that would be successful in destroying certain strongholds, releasing a crowd of prisoners, and burning or sinking many ships. The city of Algiers was bombarded almost into ruins in 1682, and the job completed a year later, after the Algerians had tossed the French consul out to the fleet, with their compliments, from the mouth of a mortar. They were fond of such jokes. Nevertheless, the city speedily recovered, and piracy, complicated by Moslem fanaticism and Turkish politics, harassed commerce during all the next century, partly because Europe was so busy in its own wars that it had no time for outside matters, and partly because it was for the advantage of certain nations (particularly of Great Britain, which, in possession of Gibraltar and Port Mahon, might have suppressed this villainy) to let the corsairs prey upon its foes—especially France. The actual result was that most or all of the European powers fell into the custom of paying to Algiers, Tunis, Tripoli, and other rulers of the Barbary (or Berber) States large sums of money as annual tribute to restrain them from official depredations upon their coasts and commerce, besides other large payments for the ransom of such Christian prisoners as each sultan’s lively subjects continued to take in spite of treaties.