It is consider that both the sinking if the USS Maine and The Lusitania were factors in US entering two different wars (the war between US and Spain and the First World War).
The USS Maine was sunk in 1898 in Cuba. The battleship was near the Cuban coast while there was a conflict between Spain and Cuban nationalists fighters. It is believed that a mine was the cause of the explosion of the USS Maine resulting in the death of hundreds of men on board. There was already support in the US for the Cuban nationalist cause and the USS Maine incident galvanized the public opinion against Spain.
The Lusitania was sunk by a German submarine in 1915 near Ireland. The Lusitania was a civilian ship (although it was also carrying military supplies to England) and its sinking had a profound impact on public opinion. It helped the US goverment obtain popular support to declare war on Germany.
