The Spanish–American War was a conflict in 1898 between Spain and the United States, the result of U.S. intervention in the Cuban War of Independence.

President William McKinley sent the USS Maine to Havana to ensure the safety of American citizens and interests, and to underscore the urgent need for reform. Naval forces were moved in position to attack simultaneously on several fronts if the war was not avoided. As the Maine left Florida, a large part of the North Atlantic Squadron was moved to Key West and the Gulf of Mexico. Others were also moved just off the shore of Lisbon, and still others were moved to Hong Kong.

At 9:40 on the evening of February 15, 1898, USS Maine sank in Havana Harbor after suffering a massive explosion that caused the deaths of approximately 260 sailors. While McKinley urged patience, and did not declare that Spain had caused the explosion, the deaths of 250 out of 355 sailors on board focused American attention. was mysteriously sunk in Havana harbor; political pressures from the Democratic Party pushed the administration of Republican President William McKinley into a war that he had wished to avoid.  Spain promised time and time again that it would reform, but never delivered. The United States sent an ultimatum to Spain demanding that it surrender control of Cuba. First Madrid declared war, and Washington then followed suit. The sinking of the battleship Maine precipitated the Spanish-American War and popularized the phrase “Remember the Maine!”

Although the main issue was Cuban independence, the ten-week war was fought in both the Caribbean and the Pacific. US naval power proved decisive, allowing expeditionary forces to disembark in Cuba against a Spanish garrison already brought to its knees by nationwide Cuban insurgent attacks and yellow fever. Numerically superior Cuban, Philippine, and US forces obtained the surrender of Santiago de Cuba and Manila.

The Battle of San Juan Hill on July 1, 1898, was a decisive battle of the Spanish–American War.  It was also the location of the greatest victory for the 1st United States Volunteer Cavalry, known as “Rough Riders”, as claimed by the press and its new commander, the future vice-president and later president, Theodore Roosevelt, who was posthumously awarded the Medal of Honor in 2001 for his action in Cuba.

The U.S. Navy’s investigation, made public on March 28, concluded that the ship’s powder magazines were ignited when an external explosion was set off under the ship’s hull. This report poured fuel on popular indignation in the U.S., making the war inevitable.  Spain’s investigation came to the opposite conclusion: the explosion originated within the ship. Other investigations in later years came to various contradictory conclusions, but had no bearing on the coming of the war. In 1974, Admiral Hyman George Rickover had his staff look at the documents and decided there was an internal explosion. A study commissioned by National Geographic magazine in 1999, using AME computer modelling, stated that the explosion could have been caused by a mine, but no definitive evidence was found.