The major world event triggered by the sinking of the Lusitania was the United States' entry into World War I. The British ocean liner was sunk by a German U-boat on May 7, 1915, resulting in the deaths of 1,198 passengers, including 128 Americans. The incident heightened tensions between Germany and the United States, as it was perceived as an attack on neutral rights. Public outrage grew in the U.S., leading to increased calls for intervention. Although the U.S. did not enter the war immediately, the Lusitania's sinking played a crucial role in shifting public opinion and eventually contributed to the U.S. declaring war on Germany in April 1917.