The Spanish American War marked the first time since the War of 1812 that the United States involved itself in a war involving a foreign nation. It also marked the beginning of the end for America's policy of self imposed isolation, and the beginning of American territorial possessions outside its continental limits.
The United States for many years had not involved itself in affairs of other nations outside the Americas. This was pursuant not only to the Monroe Doctrine but also to George Washington's admonition that the U.S. should remain "free of entangling alliances." The Spanish American War was largely precipitated by rival New York newspapers competing for subscriptions and who published lurid (and sometimes untrue) accounts of Spanish atrocities in Cuba. The war broke out after the sinking of the U.S.S. Main because of demands made by the U.S. to which it knew the Spanish would not agree. As a result of this very short war (Secretary of State John Hay called it a "splendid little war.") The U.S. gained possession not only of Puerto Rico but also Guam and the Philippines. Although the Philippines were eventually liberated, Guam and Puerto Rico remain U.S. possessions.