The sinking of the Lusitania on May 7, 1915, was a pivotal event that contributed significantly to U.S. involvement in World War I. A British ocean liner, the Lusitania was torpedoed by a German U-boat, resulting in the deaths of 1,198 passengers, including 128 Americans. This incident heightened anti-German sentiment in the U.S. and swayed public opinion towards supporting the Allies. Although the U.S. initially sought neutrality, the sinking underscored the dangers posed by unrestricted submarine warfare. It ultimately contributed to the United States abandoning its isolationist stance and declaring war on Germany in April 1917, marking a decisive shift in the course of the war.