Between April and June 1563 the Regency of Algiers launched a major military campaign to retake the Spanish military-bases of Oran and Mers el Kébir on the North African coast, occupied by Spain since 1505. The sieges of Oran and Mers El Kébir of 1563 represented a major Hispano-Algerian episode in the larger Ottoman-Habsburg wars of the Mediterranean. The Kingdom of Algiers, the Principalities of Kabyle (Kuku and Beni Abbes), and other vassal tribes combined forces as one army under Hasan Pasha, son of Hayreddin Barbarossa, and Jafar Catania. The Spanish commander brothers, Alonso de Córdoba Count of Alcaudete and Martín de Córdoba, managed to hold the strongholds of Oran and Mers El Kébir, respectively, until the relief fleet of Francisco de Mendoza arrived to successfully defeat the offensive. Background With the defeat of the Knights of Malta and the conquest of Tripoli by the Ottoman admiral Turgut Reis in 1551, and the fall of Bougie to the governor of Algiers, Salih Reis, in 1555, Oran and Mers El Kébir were, along with the island of La Goulette, the only remaining possessions of Christendom in Barbary resisting Ottoman and Moorish piracy operating along the coasts of Naples, Sicily, and the Levant. When the Ottoman commander Hasan Corso's fleet of 50 galleys besieged both towns in the Siege of Oran in 1556, it was Sultan Suleiman's order to withdraw his galleys for use in the Eastern Mediterranean that ensured Oran and Mers El Kébir could continue under Spanish control despite being weakly defended. In 1562, Hasan Pasha, son of Hayreddin Barbarossa and the Ottoman governor of Algiers, purposed to incorporate the Spanish garrisons of Oran and Mers El Kébir into the territories of Algiers. When King Philip II discovered the plan he ordered the assembly of a fleet from Barcelona to transport 4,000 soldiers as reinforcements. On October 19, 1562, a storm led to the naval disaster that became known as La Herradura. The Spanish fleet off the city of Málaga was destroyed, 24 of the 27 galleys sank, and a large number of sailors and soldiers, including Don Juan de Mendoza, Captain General of the Galleys of Spain, perished. Hassan Pasha, instructed by the Sultan Suleiman, assembled soon an army of 100,000 men among Turks, Algerines, and a large number of Janissaries. This army was supported by sea by a fleet of 30 galleys, 5 French carracks, and 15 small