Sinking of Kaiser Wilhelm der Grosse (converted to a commerce raider) off Río de Oro, Spanish Sahara, August 26, 1914: “first passenger liner to sink in World War I” (Battle of Río de Oro).
...upon travel across the North Atlantic
...upon migration between Europe and the United States
...upon U.S. policies towards immigration from Europe
Also: Commentary on changes to migration signalled by the Great War, part of the VoxEu series on "The Economics of World War I."