On April 25,1898, the United States formally declared war against Spain. The Monroe Doctrine, which since 1823 had viewed any European intervention in the Americas as a threat to U.S. security, coupled with the sinking of the U.S.S. Maine in Havana harbor precipitated the U.S. engagement. Coverage by both the Hearst newspapers and the nascent film industry solidified public support for involvement in Cuba's struggle for independence.
Within months, Spain's overseas empire, which had begun with Columbus' voyages of discovery, finally collapsed under the U.S.' two-pronged war strategy. Commodore George Dewey sailed to the Pacific the day that war was declared. On May 1 the Spanish fleet was defeated in the Philippines. The U.S. Marines and other troops, including Teddy Roosevelt and the Rough Riders, helped defeat Spanish forces in the Americas.