During the Spanish-American War, the United States' war effort against Spanish positions in the Caribbean was slow to start — a jarring contrast to Dewey’s immediate action in the Far East. Manpower and supply problems plagued the effort, resulting in a period of inaction between the declaration of war and the invasion of Cuba. A blockade of Cuban ports was instituted on April 22, 1898. Spain's Atlantic fleet, under Admiral Cervera, entered the harbor of Santiago, Cuba, on May 19, where it was blockaded by an American fleet under Rear Admiral W.T. Sampson. The immediate military objective of the United States quickly became the capture or destruction of this fleet. An army of 18,000 regulars and volunteers at Tampa, Florida, was transported to the Cuban coast east of Santiago before the end of June. Commanded by General W.R. Shafter, it stormed the heights overlooking Santiago in the battles of El Caney and San Juan Hill on July 1. With the Spanish position becoming untenable in Santiago, Cervera was ordered to lead his fleet out of the harbor. When he did come out on July 3, his fleet was totally destroyed by the Americans. The destruction of the Spanish fleet under Cervera virtually ended the war. The city of Santiago surrendered on July 16. Puerto Rico fell easily to American forces following the victory in Cuba. General Nelson A. Miles landed in Puerto Rico practically unopposed on July 25.