Exercise Tiger, or Operation Tiger was one of a series of large-scale 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 positioning itself for the landing was attacked by E-boats of Nazi Germany's Kriegsmarine, resulting in the deaths of at least 749 American servicemen.