The Spanish–American War (April 21 – August 13, 1898) was a period of armed conflict between Spain and the United States. Hostilities began in the aftermath of the internal explosion of USS Maine in Havana Harbor in Cuba, leading to United States intervention in the Cuban War of Independence. The war led to the United States emerging predominant in the Caribbean region, and resulted in U.S. acquisition of Spain's Pacific possessions. It led to United States involvement in the Philippine Revolution and later to the Philippine–American War.
The 19th century represented a clear decline for the Spanish Empire, while the United States went from becoming a newly founded country to being a medium regional power. In the Spanish case, the decadence, which already came from previous centuries, accelerated first with the Napoleonic invasion, which in turn would cause the independence of a large part of the American colonies, and later political instability (pronouncements, revolutions...