With the arrival of the Bourbons in the 18th century, Ferrol became a leading naval centre. Ferrol was made Capital of the Maritime Department of the North, formed under Ferdinand VI and Charles III for the defence of the Spanish Colonial Empire in America. Rapid improvements followed, notably under the leadership of the Marquis of Ensenada, and the position of Ferrol was made almost unassailable from the sea, the difficulties of disembarking troops on its precipitous coast being strengthened by a renewed line of fortresses and newly built castles, including that of San Carlos.