Following its declaration of war against Spain issued on April 25, 1898, the United States added the Teller Amendment asserting that it would not attempt to exercise hegemony over Cuba. Two days later Commodore George Dewey sailed from Hong Kong with Emilio Aguinaldo on board. Fighting began in the Phillipines Islands at the Battle of Manila Bay on May 1 where Commodore George Dewey reportedly exclaimed, "You may fire when ready, Gridley," and the Spanish fleet under Rear Admiral Patricio Montojo was destroyed. However, Dewey did not have enough manpower to capture Manila so Aguinaldo's guerrillas maintained their operations until 15,000 U.S. troops arrived at the end of July. On the way, the cruiser Charleston stopped at Guam and accepted its surrender from its Spanish governor who was unaware his nation was at war. Although a peace protocol was signed by the two belligerents on August 12, Commodore Dewey and Maj. Gen. Wesley Merritt, leader of the army troops, assaulted Manila the very next day, unaware that peace had been declared.
In late April, Andrew Summers Rowan made contact with Cuban General Calixto García who supplied him with maps, intelligence, and a core of rebel officers to coordinate U.S. efforts on the island. The U.S. North Atlantic Squadron left Key West for Cuba on April 22 following the frightening news that the Spanish home fleet commanded by Admiral Pascual Cervera had left Cadiz and entered Santiago, having slipped by U.S. ships commanded by William T. Sampson and Winfield Scott Schley. They arrived in Cuba in late May.
War actually began for the U.S. in Cuba in June when the Marines captured Guantánamo Bay and 17,000 troops landed at Siboney and Daiquirí, east of Santiago de Cuba, the second largest city on the island. At that time Spanish troops stationed on the island included 150,000 regulars and 40,000 irregulars and volunteers while rebels inside Cuba numbered as many as 50,000. Total U.S. army strength at the time totalled 26,000, requiring the passage of the Mobilization Act of April 22 that allowed for an army of at first 125,000 volunteers (later increased to 200,000) and a regular army of 65,000. On June 22, U.S. troops landed at Daiquiri where they were joined by Calixto García and about 5,000 revolutionaries.
U.S. troops attacked the San Juan heights on July 1, 1898. Dismounted troopers, including the African-American Ninth and Tenth cavalries and the Rough Riders commanded by Lt. Col. Theodore Roosevelt went up against Kettle Hill while the forces led by Brigadier General Jacob Kent charged up San Juan Hill and pushed Spanish troops further inland while inflicting 1,700 casualties. While U.S. commanders were deciding on a further course of action, Admiral Cervera left port only to be defeated by Schley. On July 16, the Spaniards agreed to the unconditional surrender of the 23,500 troops around the city. A few days later, Major General Nelson Miles sailed from Guantánamo to Puerto Rico. His forces landed near Ponce and marched to San Juan with virtually no opposition.
Representatives of Spain and the United States signed a peace treaty in Paris on December 10, 1898, which established the independence of Cuba, ceded Puerto Rico and Guam to the United States, and allowed the victorious power to purchase the Philippines Islands from Spain for $20 million. The war had cost the United States $250 million and 3,000 lives, of whom 90% had perished from infectious diseases.
