Exercise Tiger was intended to prepare American soldiers and seamen for the invasion of Normandy.
On the night of 27 April 1944 Slapton Sands on the coast of Devon was selected for American troops to practice their landing at Utah beach because the area resembled the French coast. It was around 2 in the morning when their convoy which included landing crafts full of American soldiers were heading towards the beach when they were suddenly attacked by German E Boats which were on a routine patrol.
By the time the fast-moving E boats had left the area and the Royal Navy arrived 639 (some reports state 749) American soldiers and seamen had been killed. A subsequent investigation discovered many who abandoned their ships and landing crafts died from hyperthermia, others died in the flames of burning oil on the surface of the sea and many soldiers wearing heavy equipment drowned because they had not been taught how to use their life preservers.
To ensure D-day remained secret those who survived were ordered not to speak of the attack, all leave was cancelled to ensure news did not leak out and these soldiers later took part in the seaborne invasion.
The fall details of the loss of American servicemen only came to the attention of the wider public in 1984 and there is now a memorial to those who were lost at Slapton Sands.