The US 4th Infantry Division lost 749 men in the attack, four times as many as they did on D-Day.
ADVERTISEMENTAn art installation of boot prints has been placed on a Devon beach to mark the 75th anniversary of a little-known Second World War tragedy.
Exercise Tiger was a rehearsal for the D-Day landings by the US 4th Infantry Division, which was ambushed by German torpedo boats in the early morning darkness of 28 April, 1944.
The Division lost 749 men in the attack – four times as many as they did on D-Day.
The eight-day exercise, carried out at Slapton due to its similarity to the Normandy landing sites, involved 3,000 ships and 300,000 soldiers and sailors. Only one British corvette provided escort for the slow-moving convoy of US Navy tank-landing ships, or LSTs, to Slapton Sands.
Nine fast-moving German torpedo boats happened upon the convoy, sank two LSTs and badly damaged a third.
The attack saw the second-highest number of US fatalities in a single day of the war, topped only by the Japanese attack on Pearl Harbor.
Survivors of the ambush were warned to keep it secret. The casualties were not announced until nearly two months after the Normandy invasion, and full details were not known until 1974, when records of the event were declassified.
The convoy was lightly guarded and because of a typographical error, the US ships were on the wrong radio frequency and unable to receive warnings.
The installation at Slapton Sands, near Stokenham, was created by artist Martin Barraud from the There But Not There charity, and will raise money for veteran employment projects.