The RMS Lusitania was sunk by a German submarine on the 7th May 1915. 1,198 people died. The Germans struck a medal in commemoration of the event, but with the wrong date (the 5th May). This prompted an outcry and allegations that the sinking was premeditated murder. The medal was also struck by the English (the example here, mounted on an unofficial plinth) as a propagandar tool.