High Quality Content by WIKIPEDIA articles! The Puerto Rican Campaign was an American military sea and land operation on the island of Puerto Rico during the Spanish–American War. The offensive began on May 12, 1898, when the United States Navy attacked the archipelago’s capital, San Juan. Though the damage inflicted on the city was minimal, the Americans were able to establish a blockade in the city’s harbor, San Juan Bay. On June 22, the cruiser Isabel II and the destroyer Terror delivered a Spanish counterattack, but were unable to break the blockade and the Terror was damaged.