المرسى الكبير
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 to capture Mers El Kébir, as Hassan was warned by several renegades that the Spanish planned to 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.