The D-Day rehearsal that cost 800 lives

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The D-Day rehearsal, codenamed Exercise Tiger, was a disaster on a grand scale with the loss of life greater than the actual invasion of Normandy just months later. But the true story was to remain a secret for decades to come.

Early on 28 April 1944, eight tank landing ships, full of US servicemen and military equipment, converged in Lyme Bay, off the coast of Devon, making their way towards Slapton Sands for the rehearsal.

So vital was the exercise that the commanders ordered the use of live naval and artillery ammunition to make the exercise as real as possible, to accustom the soldiers to what they were soon going to experience.

But a group of German E-Boats, alerted by heavy radio traffic in Lyme Bay, intercepted the three-mile long convoy of vessels.

The heavily-laden, slow-moving tank landing ships were easy targets for the torpedo boats which first attacked the unprotected rear of the convoy.

A series of tragic decisions - including the absence of a British Navy destroyer which was supposed to be escorting them, but had been ordered into Plymouth for repairs, and an error in radio frequencies - led to three of the tanks being hit by German torpedoes.

More loss of life was caused by lifejackets worn incorrectly by soldiers and the extreme cold of the sea which resulted in hypothermia.

Temporary graves were made for the Exercise Tiger casualties

The exercise that killed nearly 1,000 American servicemen was considered by US top brass to be such a disaster that they ordered a complete information blackout.

Any survivor who revealed the truth about what happened would be threatened with a court-martial.

Continue reading the main story Survivor's story When the attack happened, my ship was in the middle of a convoy of eight LSTs [Landing Ship, Tanks]. When the torpedoes went off, it was an immediate mass ball of fire all over the main deck and all over the tank deck. I realised that saving the ship was futile, so I turned my attention to trying to save men, grabbing lifejackets and passing them out. I helped 15 men over the side and I was the last man over the port side. As I crawled over, the ship was sinking fast and turning over. I dived off and got away as fast as I could to avoid being dragged under by the suction of the ship's descent. In the coming weeks I came to realise that the ordeal I survived was not to be officially acknowledged by the navy or the United States or British governments. I feel the report was classified to prevent damaging the morale of the D-Day soldiers who had to travel through those same waters to reach their destination on 6 June 1944. The sad part of the whole thing is that the surviving family members didn't know for so many years what had happened. They were told only that their loved ones were missing in action or killed in action. I estimate that at least two-thirds of those on board never made it off the ship and today their remains rest at the bottom of the English Channel.

The Allied commanders were concerned officers who went missing during the attack could have ended up in German hands, where they might reveal the Allied intentions for the D-Day landings.

The commanders even considered changing details of the operation.

However, the bodies of every one of those officers with "BIGOT"-level clearance, a codename for a security level beyond Top Secret, were found and the tactics of D-Day were deemed to be secure.

An article in the US Stars and Stripes magazine following World War Two said family members of the dead were given no information other than what was in the original message about the death.

The family of Gunner's Mate 3rd Class Thanuel Shappard only knew he had died on 28 April 1944.

In the late 1980s, while watching a documentary about Exercise Tiger, his mother noticed the date was the same as her son's death.

It was only after researching the exercise it was confirmed Mr Shappard had been aboard Landing Ship, Tank (LST) 531, which was torpedoed and sunk by the German E-boats.

Even before the military exercise, villages surrounding Slapton Sands had been evacuated, involving the clearance of 30,000 acres and 3,000 men, women and children by the end of 1943.

As local resident Ken Small pounded the beach along Slapton Sands in Devon 40 years later, little did he know that the discovery of shrapnel, military buttons, bullets and pieces of military vehicles would lead to an all-consuming mission to tell the world the story that had so long been forgotten.

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It was only after a local fisherman told Mr Small of an "object" some three-quarters of a mile out to sea that Mr Small's desire to find out the truth was awoken.

The former hotelier ventured out to sea in his boat with his friend and a few divers, and embedded in 60ft (18m) of water they found an American Sherman tank intact on the seabed - and that tank unravelled the story.

Ken Small and Laurie Bolton at the World War Two tank after it had been rescued from the sea

After negotiations over several years, Mr Small bought the vehicle from the US government for $50, finally recovering it from the sea in May 1984.

Now, 70 years on from its sinking, the tank has not only become a war memorial, but also the place to remember Mr Small.

Thanks to his efforts, the Sherman Tank Memorial Site was officially recognized by the US Congress and acknowledged by the addition of a bronze plaque.

Continue reading the main story 'One tragedy among many' News of what happened remained a secret for a matter of months - the Germans could not find out about it. Following D-Day, Operation Tiger did appear in reports and the American Army magazine Stars and Stripes. In terms of the dead, that was a loss of the men's lives, but a bad day in the office for the admirals - it was one tragedy among many. There was never a cover-up but the story was lost from the public. Ken Small brought that story back to the public's attention. What he did was discover the story for himself and make many, many more people aware of it. Without Ken Small the tale would have merely been a footnote on the story of the war, so we should all be very thankful for what he did. Ken Small unearthed the story and told it for what it was.

Mr Small's efforts to establish a memorial received letters of gratitude and appreciation not only from relatives and families of the dead American servicemen, but also a letter from then US president Ronald Reagan thanking him for his efforts.

In 2014, on the 10th anniversary of his death, Mr Small was recognised with a plaque on the tank he discovered.

Mr Small told the story of Exercise Tiger and his discoveries in a book called The Forgotten Dead.

In it he said: "Over the last 17 years it has been my crusade to ensure a proper memorial for the men who lost their lives that night.

"I felt proud during the service of commemoration, and I still feel proud now, that at long last these men have a just memorial for their sacrifice.

"I have always considered it was a wrong which should be put right and I have always worked to that end."

"My father campaigned tirelessly for a memorial to ensure that the sacrifices made by these young men were recognised," Mr Small's son Dean said.

"Also, for those who lost a loved one, there is now a place to visit and remember them."

A plaque now sits on the tank marking Ken Small's determination to tell the story of Exercise Tiger

Laurie Bolton from Kingsburg, California, whose uncle Sgt Louis Bolton died during the exercise, has been visiting Slapton Sands for the past 20 years.

Ms Bolton said she had been "honoured" to unveil the plaque.

She said: "The Tank Memorial gives us a tangible place to come and pay tribute to our loved ones who died, as well as a place of remembrance for their sacrifice."