For more than two hundred years the corsairs of the Barbary coast had been the terror of the Christian Mediterranean. Sailing from Algiers, Tunis, and Tripoli, semi-independent vassals of the Ottoman sultan, they seized ships and raided coastal villages, and the people they carried off, sold into slavery across North Africa, were a pillar of those states' economies. For Spain, whose southern shore and eastern Levante lay directly in their path, the corsairs of Algiers were a wound that would not close. After the peace of 1748 left the Spanish Navy idle, the Marquis of Ensenada turned it against this old enemy, sending divisions to harry the Barbary coast. In 1751, off Cape St Vincent, one such patrol destroyed the Algerian flagship Danzik. Her consort escaped and took her place as the new flagship of Algiers. Her name was Castillo Nuevo, and seven years later she would sail straight into a Spanish squadron once more.

On 2 June 1758, three Spanish 68-gun ships of the line, Soberano, Vencedor, and Héctor, stood out from Cartagena under Captain Isidoro García del Postigo to sweep the coast clear of raiders. A week later, at eight in the morning on 9 June, they sighted three suspicious sail near Cape Palos and gave chase. One of the three, a captured prize ship, broke away and ran to the south-southeast, while the two Algerian warships turned to cover her escape: the 60-gun Castillo Nuevo, flagship under Arráez Mahamud Rais, and the 40-gun frigate Caravela, commanded by a European renegade named Achí Mustafá. The Spaniards ran up British colours to close the distance, then hauled them down, raised their own, and opened fire in the late afternoon. Héctor peeled away after the fleeing frigate; the other two bore down on the flagship.

What followed was less a brawl than a slow, deliberate demolition. Soberano and Vencedor held off at a distance, using the longer reach and heavier weight of their guns to batter the Castillo Nuevo while staying beyond her best reply. It was maddeningly patient work: at that range the shot lost much of its force, and the Algerian crew fought on with stubborn courage hour after hour. The Spaniards switched from solid shot to shrapnel, sparing the hull so they might carry the ship off as a prize. By eleven at night the flagship was a dismasted hulk, her rigging shot away; at midnight the exhausted attackers broke off to rest. At one in the morning Mahamud Rais finally surrendered. As the light came up, Spanish boats pulled alongside the sinking ship to take off whoever still lived.

The reckoning was stark. Aboard the Castillo Nuevo more than a hundred Algerian sailors had been killed and forty-four drowned; three hundred and six were taken prisoner, Mahamud Rais among them. And in her hold were fifty-three enslaved Europeans, Dutchmen, Germans, and one Irishman, now suddenly free. Spanish losses across both ships came to two dead and eleven wounded, a margin so lopsided that one Spanish historian put it down to the corsairs mishandling their own guns. The frigate Caravela, run down against the African coast by Héctor, was lost when a squall drove the two ships apart; a wreck found days later near Alhucemas was taken for her. The prize that had started the whole affair proved to be a richly laden merchantman out of Hamburg, which is why the corsairs had thrown away two warships to save her. It was the third Algiers flagship Spain had destroyed in that century, and though the raids would not end for another generation, this was one of the blows that began their long decline.