How did the sinking of the Lusitania in 1915 affect World War 1?

The sinking of the Lusitania in 1915 heightened tensions between the United States and Germany, as the attack resulted in the deaths of 128 American citizens. It galvanized American public opinion against Germany and contributed to calls for the U.S. to enter World War I. Although the U.S. did not join the war immediately after the sinking, it marked a significant shift in sentiment that eventually led to American involvement in 1917, altering the course of the conflict. The incident underscored the dangers of unrestricted submarine warfare and influenced international perceptions of Germany's conduct in the war.