Moorish Andalusi traders establish the city of Oran in 903.

…Oran in 1082-83, as well as …

Tashfin ibn Ali, in attacking the Almohads, under the leadership of Abd al-Mu'min, in the Oran area, finds himself besieged for several days by the Almohad forces and finally opts for an escape by sea.

He subsequently calls on a fleet from Almeria, burns his military encampment and while trying to join the port by night on horseback, falls off a cliff and dies in March 1145.

He is succeeded first by his oldest son Ibrahim ibn Tashfin, who is still an infant, and will soon after be replaced by Tashfin’s brother, Ishaq ibn Ali.

Almoravid ruler Ali ibn Yusuf was a pious non-entity: while his empire had fallen to pieces under the combined action of his Christian foes in Iberia and the agitation of the Almohads (the Muwahhids), a group of Masmuda Berbers living in the Atlas Mountains in Morocco, he had fasted and prayed.

Since Ali ibn Yusuf's death in 1142, his son Tashfin ibn Ali has lost ground rapidly before the Almohads, and in 1146 he is killed by a fall from a precipice, while endeavoring to escape after a defeat near Oran.

Tlemcen’s port city is Oran, on the northwestern Mediterranean coast of Algeria.

It excels in the export of lead, wool, skins, fine burnous, carpets, haïks, cumin, nuts, and galls, as well as enslaved Sub-Saharan Africans.

The Portuguese had launched a failed expedition to capture the city in July 1501.

Oran at this time numbers twenty-five thousand inhabitants and counts six thousand fueros.

Navarro, on the orders of Cardinal Francisco Jiménez de Cisneros, captures the city on May 17, 1509.

The occupying forces set fire to the books and archives of the town.

...Oran (1509), ...

Emperor Charles V arrives at Oran in May 1518 and is received here by Sheikh Buhammud and the Spanish governor of the city, Diego de Córdoba, Marquess of Comares, who commands a force of ten thousand Spanish soldiers.

Joined by thousands of Bedouins, …

The Ottoman Turks have by 1555 nearly cleared the Spanish presence from all Algeria, save for Oran, on the northwestern Mediterranean coast.

The siege of Oran, by land and sea, is unsuccessful and has to be lifted in August 1556 when the Ottoman fleet of forty galleys is recalled for duty in the East Mediterranean.

Spain is to hold Oran, which had been the object of Cardinal Cisneros’ successful 1507 crusade, for three centuries, thanks in part to the alliance formed by the city’s governor, Count d'Alcaudete, with Mohammed ash-Sheikh against the Ottomans.

The Ottoman admiral Turgut Reis having conquered of Tripoli from the Knights of Malta in 1551, and Bougie having fallen in 1555 to the governor of Algiers, Salih Reis, the towns of Oran and Mers El Kébir remain as the only Christian strongholds in Barbary, along with the island of La Goulette, which help fight the Ottoman and Moorish pirates who constantly plunder and raze the coasts of Naples, Sicily and the Levant.

An Ottoman fleet composed of fifty galleys under the command of the renegade Hasan Corso had besieged both cities in 1556 in the Siege of Oran, but the Sultan Suleiman ordered had ordered the seige lifted and the galleys withdrawn to serve in the Eastern Mediterranean, so both Mers El Kébir and Oran remain in Spanish hands despite the poor state of their defenses.

Hasan Pasha, son of Hayreddin Barbarossa and Ottoman governor of Algiers, intends to conquer both towns to incorporate them into their territories of Algiers.

King Philip II, who is aware of Hassan's intentions, had ordered the assembly a fleet in Barcelona that would transport four thousand 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.

Twenty-four of the twenty-seven galleys sunk, and a large number of sailors and soldiers, including Don Juan de Mendoza, Captain General of the Galleys of Spain, perished.

Hasan Pasha, on the orders of Suleiman, soon assembles an army of one hundred thousand men including Turks, Algerines and a large number of Janissaries. This army is supported at sea by a fleet of thirty galleys, five French carracks and fifteen small vessels under the command of Jafar Catania, governor of Tlemcen. With these forces Hassan goes to Mers El Kébir, a stronghold he considers essential to the capture of Oran.

Alonso and Martin de Córdoba had meanwhile received supplies, gunpowder, tools and a few soldiers from Málaga.

To hold together both towns in order to help each other, they had decided to construct two forts: San Miguel, located on the hill that separated Oran from Mers El Kébir, and Todos los Santos, facing the second town.