Spanish-American War

Congress declared war on Spain on 25 April 1898^[1], ten weeks after the battleship USS Maine exploded at anchor in Havana harbor on 15 February, killing 266 American sailors. The cause of the explosion was never conclusively established — Hyman Rickover's 1976 study concluded an internal magazine fire was the most likely explanation, while the 1898 U.S. Navy court of inquiry blamed an external mine and laid responsibility on Spain — but the political effect at the time was immediate. The Hearst and Pulitzer "yellow press" had been cultivating American sympathy for the Cuban insurrection against Spanish rule since 1895, and the Maine supplied the catalyst.

The underlying Cuban conflict ran from José Martí's February 1895 declaration of revolution through the brutal Spanish counterinsurgency campaign of General Valeriano Weyler — whose "reconcentración" policy of relocating rural civilians into garrison towns is conservatively estimated to have killed at least 100,000 Cubans through starvation and disease. American newspaper coverage of the camps, combined with substantial U.S. commercial interests in Cuban sugar and tobacco, generated sustained domestic pressure for intervention through 1896 and 1897. The McKinley administration negotiated last-minute Spanish concessions in April 1898 — Madrid agreed to suspend the reconcentración and grant Cuban autonomy — but Congress had already moved past mediation, and the joint resolution authorizing war passed both chambers within two weeks of the April 11 war message.

The war was also the moment American imperial strategy crossed from continental to maritime. Alfred Thayer Mahan's 1890 The Influence of Sea Power upon History had argued for a U.S. fleet and an isthmian canal as the foundations of a Great-Power future; the Roosevelt circle (Theodore Roosevelt as Assistant Secretary of the Navy in 1898; Henry Cabot Lodge in the Senate) explicitly favored a war that would generate the strategic assets the Mahanian program required. Commodore George Dewey's Asiatic Squadron had standing orders to attack Manila Bay in the event of war — orders Dewey received from Roosevelt on 25 February 1898, ten days after the Maine — which is why a war ostensibly about Cuba produced an American empire in the Philippines.

Spain ceded or relinquished control over territories including Puerto Rico, Guam, and the Philippines; Cuba became formally independent under U.S. influence.

The Treaty of Paris of 10 December 1898^[1] ended the war in less than four months of fighting and made the United States an overseas imperial power. Spain ceded Puerto Rico and Guam to the United States, ceded the Philippines for a $20 million payment, and relinquished sovereignty over Cuba. Cuba achieved formal independence under the 1903 Platt Amendment^[1], which authorized U.S. intervention in Cuban affairs and a U.S. naval base at Guantánamo Bay; the amendment was abrogated in 1934 but the base remains. The Hawaiian Islands, separately, were annexed by the Newlands Resolution in July 1898^[2] under the wartime strategic logic of mid-Pacific coaling stations.

Filipino independence forces under Emilio Aguinaldo, who had cooperated with the U.S. against Spain in the expectation of independence, resisted annexation in the Philippine-American War of 1899–1902 (with insurgency continuing in the Moro regions through 1913). That war was substantially longer and bloodier than the Spanish-American War that produced it: roughly 4,200 U.S. military deaths, an estimated 20,000 Filipino combatant deaths, and somewhere between 200,000 and a million Filipino civilian deaths from war, famine, and disease — depending on the estimate. It was the United States' first counterinsurgency campaign and one of its most lethal.

Domestically, the war crystallized the imperialist and anti-imperialist political alignments of the early twentieth century: the Anti-Imperialist League (Mark Twain, Andrew Carnegie, William Jennings Bryan, William James, and Samuel Gompers, among others) argued that overseas colonies were incompatible with republican government, while expansionists including Theodore Roosevelt and Albert Beveridge argued the reverse. The Insular Cases of 1901–1922 invented the doctrinal category of "unincorporated territory" to govern the new possessions — a doctrine still in force for Puerto Rico, Guam, the U.S. Virgin Islands, the Northern Mariana Islands, and American Samoa. Roosevelt's wartime celebrity with the Rough Riders at the July 1898 charge up Kettle Hill (popularly remembered as San Juan Hill) propelled him to the vice-presidency in 1900 and, after McKinley's September 1901 assassination, to the presidency.