German submarine U-20 sank RMS Lusitania off Ireland on 7 May 1915.
The British ocean liner was traveling from New York to Liverpool when U-20 fired a torpedo near the Old Head of Kinsale. Lusitania sank rapidly, killing nearly 1,200 people, including 128 Americans. The disaster caused international outrage and intensified debate over Germany’s unrestricted submarine warfare.
Germany argued that the ship carried contraband and had been treated as an enemy vessel. The sinking nevertheless damaged German diplomatic standing, especially in the United States, although America did not enter World War I until 1917.
U-20 was later lost in 1916 after striking a mine near Denmark. Lusitania is sometimes confused with other wartime liner sinkings, but the submarine directly associated with the event was U-20.