The 1898 war, which lasted only a matter of months (late April to mid-August), was fought over the liberation of Cuba. During the 1870s the Cuban people rebelled against Spanish rule. But once that long rebellion had been put down, peace on the Caribbean island did not hold: worsening economic conditions prompted revolution in 1895. American leaders, the bloody American Civil War (1861–65) still in their memories, feared that while the Cuban rebels could not win their battle against the Spanish, neither were the Spanish strong enough to fully put down the insurrection. Meanwhile, the American public, fed by a steady stream of newspaper accounts reporting oppressive conditions on the island, increasingly supported U.S. intervention in the Cuban conflict.

In November 1897 President William McKinley (1843–1901) did intervene, but it was through political, rather than military, pressure. As a result, Spain granted Cuba limited self-government within the Spanish empire. However, the move did not satisfy the Cuban rebels, who were determined to achieve independence from Spain; the fighting continued. Rioting broke out in Havana, and in order to protect Americans living there, the United States sent the battleship Maine to the port on January 25, 1898. On February 15, an explosion blew up the Maine, killing more than 200 people. Blame for the blast was promptly—and history would later conclude wrongly—assigned to Spain. While President McKinley again made several attempts to pressure Spain into granting Cuba full independence, it was to no avail. Nevertheless, on April 19, the U.S. Congress passed a joint resolution recognizing an independent Cuba, disclaiming American intention to acquire the island, and authorizing the use of the American army and navy to force Spanish withdrawal. On April 25, the United States formally declared that the country was at war with Spain.

In the months that followed, American forces battled the Spanish and Spanish loyalists in Cuba and the Spanish-controlled Philippines. There was also military activity on Puerto Rico, however, the American forces there met little resistance. Once Santiago, Cuba, was surrendered by the Spanish after the battle at San Juan Hill in July 1898, it would only be a matter of weeks before a cease-fire was called and an armistice was signed (on August 12), ending the brief war.