Exercise Tiger
Exercise Tiger, or Operation Tiger was one of a the rehearsals for the D-Day invasion of Normandy. Held in April 1944 on Slapton Sands in Devon, it proved fraught with difficulties. Coordination and communication problems resulted in friendly fire injuries during the exercise and an Allied convoy preparing for the landing was attacked by E-boats of Nazi Germany's Kriegsmarine, resulting in the deaths of at least 749 American servicemen. Because of the impending invasion of Normandy, the incident was kept secret and was only minimally reported afterwards.