raided Calabria. These losses prompted Venice to ask Pope Paul III to organize a "Holy League" against the Ottomans. In February 1538, Pope Paul III succeeded in assembling a Holy League (composed of the Papacy, Spain, the Holy Roman Empire, the Republic of Venice and the Maltese Knights) against the Ottomans, but Barbarossa's forces led by Sinan Reis defeated its combined fleet, commanded by Andrea Doria, at the Battle of Preveza in September 1538. This victory secured Ottoman dominance over the Mediterranean for the next 33 years, until the Battle of Lepanto in 1571. In the summer of 1539, Barbarossa captured the islands of Skiathos, Skyros, Andros and Serifos and recaptured Castelnuovo from the Spanish, who had taken it from the Ottomans after the battle of Preveza. He also captured the nearby Castle of Risan, and with Sinan Reis, later assaulted the Venetian fortress of Cattaro and the Spanish fortress of Santa Veneranda near Pesaro. Barbarossa later took the remaining Christian outposts in the Ionian and Aegean Seas. Venice finally signed a peace treaty with Sultan Suleiman in October 1540, agreeing to recognize the Ottoman territorial gains and to pay 300,000 gold ducats. In 1540 Barbarossa led a crew of 2,000 men and captured and ransacked the town of Gibraltar. He left Gibraltar after taking 75 prisoners which removed a significant percent of Gibraltar’s population, he ultimately eliminated the town of almost an entire generation of Gibraltarians. In September 1540, Emperor Charles V contacted Barbarossa and offered him to become his Admiral-in-Chief as well as the ruler of Spain's territories in North Africa, but he refused. Unable to persuade Barbarossa to switch sides, in October 1541, Charles himself laid siege to Algiers, seeking to end the corsair threat to the Spanish domains and Christian shipping in the western Mediterranean. The season was not ideal for such a campaign, and both Andrea Doria, who commanded the fleet, and Hernán Cortés, who had been asked by Charles to participate in the campaign, attempted to change the Emperor's mind but failed. Eventually, a violent storm disrupted Charles's landing operations. Andrea Doria took his fleet away into open waters to avoid being wrecked on the shore, but much of the Spanish fleet went aground. After some indecisive fighting on land, Charles had to abandon the effort and withdraw his severely battered force. Franco-Ottoman alliance In 1543, Barbarossa headed towards Marseilles to assist France, then