On the night of April 28, 1944, more American soldiers were killed rehearsing for D-Day than were killed storming Utah Beach on D-Day itself. It happened in secret, and the survivors were ordered to take it to their graves. Most did.
Six weeks before the real invasion, the US Army staged a full dress rehearsal at Slapton Sands in Devon, a beach chosen because it looked almost exactly like the Normandy shore codenamed Utah. Eisenhower wanted it realistic, so they used live ammunition. That decision killed men before the enemy even arrived, when timing went wrong and incoming troops were shelled by their own naval guns on the sand. But the worst was still hours away.
Just after midnight, a convoy of eight tank landing ships, packed with men, trucks and fuel, was crawling across Lyme Bay in a long slow line. Out in the dark, nine German E-boats had slipped in from Cherbourg, and they could not believe what they were seeing. The convoy was nearly defenseless. One escort ship had been damaged in a collision and sent to port, never replaced. Worse, a typo had put the landing ships and their lone escort on different radio frequencies, so the warnings that could have saved them were broadcast to no one.
The E-boats opened fire. One ship burst into flames, another was hit and went under in about six minutes, taking hundreds down with her. Men poured into water barely above freezing. Then the cruelest detail: they had been issued life belts but never trained to wear them, so many strapped them around the waist instead of under the arms. When they jumped, the weight of their packs flipped them face-down, and the belts held them there. Hundreds drowned upside down in their own life jackets.
By dawn, around 749 Americans were dead, more than would die taking the actual beach on June 6. And the generals had a problem bigger than the bodies. Ten of the officers aboard held BIGOT clearance and knew the time and place of the entire invasion. If even one had been pulled alive from the sea by the Germans, D-Day would have had to be cancelled. Frantic teams searched the water for all ten. Every body was recovered. The secret held.
So the whole thing was buried. Bodies quietly interred, paperwork sealed, survivors warned that talking meant court martial. The records were not declassified until 1974. For decades these men had no monument and no mention. They died twice, once in the water and once in the silence that followed.
It was called Exercise Tiger. Now you know.