1. Sinking of USS Maine. The sinking of the USS Maine is regarded as the primary reason for the US declaration of war against Spain. On 15th February 1898, the USS Maine exploded and sank in Havana Harbor. The U.S. Navy conducted an investigation and concluded that a Spanish mine had caused the explosion, although, the Spanish government denied responsibility for the incident.
2. Human rights abuses in Cuba. Human rights abuses committed by the Spanish government against the Cuban population were another reason for the U.S. declaration of war. Cuba had been struggling for independence from Spain for several years, and the U.S. government was concerned about the treatment of Cuban civilians. The U.S. public was also strongly sympathetic to the Cuban cause.