of war. Meanwhile, in the Caribbean theater, a large force of regulars and volunteers gathered near Tampa, Florida, for an invasion of Cuba. After lengthy delays, the army, led by Major General William Rufus Shafter, on June 22, landed near Santiago de Cuba. Shafter's army engaged the Spanish forces on July 2 in the Battle of San Juan Hill. In an intense day-long battle, the American force was victorious, although both sides suffered heavy casualties. The next day, Spain's Caribbean squadron, which had been sheltering in Santiago's harbor, broke for the open sea and was destroyed by the North Atlantic Squadron in the largest naval battle of the war. Shafter laid siege to the city of Santiago, which surrendered on July 17, placing Cuba under effective American control. McKinley and Miles also ordered an invasion of Puerto Rico, which met little resistance when it landed in July. The distance from Spain and the destruction of the Spanish navy made resupply impossible, and the Spanish government began to look for a way to end the war. Peace and territorial gain McKinley's cabinet agreed with him that Spain must leave Cuba and Puerto Rico, but they disagreed on the Philippines, with some wishing to annex the entire archipelago and some wishing only to retain a naval base in the area. Although public sentiment seemed to favor annexation of the Philippines, several prominent political leaders—including Democrats Bryan, and Cleveland, and the newly formed American Anti-Imperialist League—made their opposition known. McKinley proposed to open negotiations with Spain on the basis of Cuban liberation and Puerto Rican annexation, with the final status of the Philippines subject to further discussion. He stood firmly in that demand even as the military situation in Cuba began to deteriorate when the American army was struck with yellow fever. Spain ultimately agreed to a ceasefire on those terms on August 12, and treaty negotiations began in Paris in September 1898. The talks continued until December 18, when the Treaty of Paris was signed. The United States acquired Puerto Rico and the Philippines as well as the island of Guam, and Spain relinquished its claims to Cuba; in exchange, the United States agreed to pay Spain $20 million (equivalent to $ million in ). McKinley had difficulty convincing the Senate to approve the treaty by the requisite two-thirds vote, but his lobbying, and that of Vice President Hobart, eventually saw success,