Sieges of Oran and Mers El Kébir The sieges of Oran and Mers El Kébir took place between April and June 1563 during the Ottoman - Habsburg struggle for the control of the Mediterranean when a huge Ottoman army under the command of Hasan Pasha , son of Hayreddin Barbarossa , and Jafar Catania , tried to conquer the Spanish - controlled strongholds of Oran and Mers El Kébir on the North Africa n coast , defended respectively by Alonso de Córdoba , Count of Alcaudete , and his brother Martín de Córdoba . The stubborn defense of the Spanish and the arrival of a relief fleet under Francisco de Mendoza frustrated the Ottoman intentions . Background . After the conquest of Tripoli to the Knights of Malta by the Ottoman admiral Turgut Reis in 1551 , and the fall of Bougie to the governor of Algiers , Salih Reis , in 1555 , the towns of Oran and Mers El Kébir remained as the only Christian strongholds in Barbary , along with the island of La Goulette , which helped fight the Ottoman and Moorish pirates who constantly plundered and razed the coasts of Naples , Sicily and the Levant . An Ottoman fleet composed of 50 galleys under the command of the renegade Hasan Corso besieged both cities in the Siege of Oran in 1556 , but the Sultan Suleiman ordered lift the siege to withdraw the galleys to serve in the Eastern Mediterranean , so both Mers El Kébir and Oran remained in Spanish hands despite the poor state of their defenses . In 1562 , Hasan Pasha , son of Hayreddin Barbarossa and Ottoman governor of Algiers , purposed to conquer both towns to incorporate them into their territories of Algiers . King Philip II , who was aware of Hassan ' s intentions , ordered assemble a fleet in Barcelona which would transport 4 , 000 soldiers to reinforce the small garrisons of Oran and Mers El Kébir . These forces , however , never reached their destination due to a storm that destroyed the fleet on October 19 off the city of Málaga . 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 vessels under the command of Jafar Catania , governor of Tlemcen . With these forces Hassan went to Mers El Kébir , stronghold whose dominion he considered essential to capture Oran . Meanwhile , Alonso and Martin de Córdoba had received supplies , gunpowder , tools and a few soldiers from Málaga . To hold together both towns in order to help each other , they decided built two fort s : " San Miguel " , located on the hill that separated Oran from Mers El Kébir , and " Todos los Santos " , facing the second town . Siege . Forts San Miguel and Todos los Santos . The siege began on April 3 , 1563 , when Ottoman troops massively attacked the tower of " Todos los Santos " , defended by 200 Spanish soldiers . The fierce resistance of the fort ' s garrison , along with artillery support from Mers El Kébir , inflicted heavy casualties on the attackers . However , once the Ottoman cannons tore down the walls , the fort was soon taken . Meantime Jafar ' s galleys blocked Mers El Kébir to prevent the city to be relieved from Oran . Ottoman ' s main objective was capture Mers El Kébir , as Hassan was warned by several renegade s that the Spanish planned abandon Oran to concentrate on the defense of the other town . Therefore , he destined most of his troops to take the fort of " San Miguel " , a key point of the Spanish defense , while only a few troops remained blocking Oran . San Miguel ' s fort was attacked during 22 days by 24 , 000 infantry and 400 cavalry soldiers . His few defenders rejected Hassan ' s offer of surrender and successfully repelled six assaults which left the moat full of dead Janissaries . Among the Ottoman casualties was the governor of Constantine , whose body could be recovered by his men with the permission of Martín de Córdoba . However , despite the stubbornness of the defense , the reinforcements sent from Mers el Kébir were not enough to continue fighting , and on May 8 , under cover of darkness , the Spanish survivors retreated to the town . Siege of Mers el Kébir . Once occupied the fort , the Ottoman troops surrounded the city , digging trenches around and placing artillery to break down the walls . On a nearby hill were also installed several culverin s to bombard the inner town . Martín de Córdoba , who had less than 500 men available to defend the city , prepared for the assault . This one took place on 20 May . Hassan sent ahead to 12 , 000 alarabs to break the resistance of the Spanish harquebusiers and facilitate the assault to two columns of regular troops which would attack secondly . Despite the heavy losses they suffered , the alarabs managed to scale the walls and raise the Ottoman flag on the battlement s . However , the Spanish expelled them soon . In that attack nearly 2 , 500 men died , mostly falling into the moat around the town . In the following days took place more assaults which also failed with great loss of life , although the Spanish situation he had become desperate . On June 6 Hassan was about to order the final assault , when a relief fleet took his army by surprise . King Philip II had ordered a fleet to be organized in Cartagena in order to attack Hassan ' s army and force it to lift the siege . Under the command of Francisco de Mendoza , who was seconded by Álvaro de Bazán and Andrea Doria , 34 galleys coming from Barcelona , Naples , Genoa , Savoy , and Malta , had embarked 4 , 000 soldiers and many volunteer knights , and had sailed to Mers el Kébir . Hassan , fearing to be trapped between the Spanish reinforcements and Mers El Kébir , ordered his troops to retreat hastily . The tents could be saved , but guns , clothing and tools were left in the field . The Ottoman fleet was not so lucky , and several of its ships , including four of the French carracks , were captured . Aftermath . After disembarking reinforcements and supplies at Oran and Mers El Kébir , Francisco de Mendoza ' s fleet returned to Spain . King Philip II , informed about the development of the siege , decided to reward Martín de Córdoba and Francisco Vivero , commanding officer of Fort " San Miguel " , for keeping these two crucial strongholds in Spanish hands . In fact , this allowed the capture the following year of Peñón de Vélez de la Gomera , a success which was followed in 1565 by the decisive defense of Malta against the fleet of Turgut Reis . Several years later , in 1574 , it was discussed at the Spanish court whether or not to abandon Oran and Mers El Kébir . King Philip II ordered Vespasian Gonzaga Colonna , Prince of Sabbioneta and Duke of Trayecto , to make a comprehensive report about the situation of both towns . Gonzaga advised to abandon Oran but to keep Mers El Kebir . However , marshal Juan Muñoz sent to the king a report by Sancho de Leyva advising to keep both strongholds . Philip II finally opted for the advice of Leyva .