A secret rehearsal for D-Day killed more Americans than Utah Beach itself — 749 dead, sunk by E-boats and friendly fire, then hushed up for months.
Exercise Tiger was a massive D-Day rehearsal held at Slapton Sands, Devon in late April 1944, chosen because its beach closely resembled Utah Beach in Normandy. About 3,000 local residents were evacuated to make way for 30,000 U.S. troops practicing amphibious assault techniques.
On April 27, a live-fire practice assault went catastrophically wrong. Admiral Moon delayed the start by 60 minutes due to landing ship delays, but not all vessels received the updated order — causing the second wave to come under friendly fire from their own forces, reportedly killing around 450 men.
In the early hours of April 28, nine German E-boats from Cherbourg intercepted Convoy T-4 crossing Lyme Bay. The convoy's escort had been stripped to a single corvette after HMS Scimitar collided with an LST and left for repairs, and its replacement arrived too late.
Two LSTs were torpedoed and sunk — LST-531 went down in just six minutes. In total, 749 Americans died (551 Army, 198 Navy), with hundreds more wounded, making it one of the deadliest single incidents for U.S. forces before D-Day itself.
Many men drowned not from the attack but from a simple training failure: soldiers had been taught to wear their inflatable life belts around the waist instead of under the arms. When their heavy combat packs hit the water, the belts flipped them face-down and they couldn't right themselves.
Ten American officers with BIGOT clearance — classified knowledge of D-Day's exact timing, landing beaches, and Ranger targets at Pointe du Hoc — were missing after the attack. Allied commanders nearly postponed the entire D-Day invasion until all ten were confirmed dead, not captured by the Germans.
Survivors were sworn to secrecy to protect the D-Day invasion plan. The Army suppressed the true casualty count for months; when figures were finally released in August 1944, they were lower than the 749 Admiral Moon had documented, and the disaster stayed largely unknown to the public for decades.
The catastrophe forced three critical changes before June 6: U.S. and British forces standardized their radio frequencies (a communication gap that left them unable to coordinate during the attack), troops received proper life jacket training, and small-craft rescue plans were added to D-Day's logistics.
Exercise Tiger was only brought to public attention through the persistence of one man — Ken Small, a Devon resident who found evidence of the disaster while beachcombing in the 1970s. He spent years recovering a sunken Sherman tank, finally raising it in 1984, and campaigned to have the victims' names publicly memorialized.