Final answer:
President McKinley sent the USS Maine to Havana in January 1898 to protect American interests, which later exploded under mysterious circumstances, contributing to the start of the Spanish-American War.
Step-by-step explanation:
During heightened tensions in Cuba and concerns over the safety of American citizens and property, President McKinley ordered one of the U.S. Navy's newer battleships, the USS Maine, to the port of Havana in January 1898. This action was taken with the approval of Spain and ostensibly to provide security and a potential means for evacuation.
The arrival of the USS Maine initially seemed to ease tensions, but the situation dramatically changed when an explosion sank the ship on February 15, 1898, leading to the deaths of over 250 American sailors. Although later investigations suggested the explosion was likely an accident, at the time, sensationalist journalism spurred public outcry and the rallying cry "Remember the Maine!" contributing to the outbreak of the Spanish-American War.