The correct answer to this open question is the following.
On February 15, 1898, US President William McKinley understood that probably diplomacy was not the only way to solve the situation in Cuba. The USS MAin ship had been sunk by the Spanish Navy. Some theories stated that it had not been the Spaniards who sank the USS Main, but a mine. A lot of controversies started on this issue. Using this sinking as the main argument, President McKinley asked Congress a declaration of war against Spain on April 20, 1898. After four months of armed conflicts, the United States won the Spanish-American War.
