Unsung American D-Day troops killed by Nazis in British waters as they rehearsed for the momentous landings have been remembered in a poignant art installation.
Bootprints of 749 GIs have been laid out on Slapton Sands, in Devon, to mark the 75th anniversary of Exercise Tiger, the secret mission to prepare for the Allied invasion of Normandy.
The troops were killed on April 28 1944 when a Royal Navy convoy carrying them was torpedoed by fast-moving E-boats from Nazi Germany's Kriegsmarine.
More people died during the exercise than in the D-Day landing at Utah Beach - with many soldiers sinking and drowning during the exercise weighed down by their heavy kit and sodden clothes.
There But Not There artist Martin Barraud working on an installation of 749 pairs of bootprints at Slapton Sands, Devon, to mark the 75th anniversary of Exercise Tiger where 749 American soldiers where killed while rehearsing for the D-Day invasion of Normandy
749 footprints cover the beach for 50 metres, representing the troops who lost their lives during the D-Day rehearsal
Artist Martin Barraud worked with a team to lay down 749 foot prints in the sand at Slapton, Devon, commemorating the previously unreported deaths of Exercise Tiger
More than 1,200 allied soldiers were killed during a D-Day training mission at Slapton Sands in Devon in April 1944
Slapton Sands in Devon was used because it resembled Utah beach in Normandy which was going to be a D-Day target
The haunting episode was kept quiet over fears the Germans would realise the exercise had been planned as a rehearsal for D-Day, which would take place five weeks later.
Artist Martin Barraud created the installation which was unveiled by the Remembered charity and will raise money for veteran employment projects.
To commemorate the 75th anniversary of Exercise Tiger and remember its victims, charity 'There But Not There' has installed the moving memorial made up of 749 pairs of bootprints on the beach at Slapton Sands, in South Devon.
The installation, over 50 metres long, will be unveiled today.
HMS Azalea, pictured, was part of the training exercise and spotted nine German E-boats approaching, but a radio error prevented allied forces from intercepting the attacking vessels before the could open fire killing 749 men
Residents in Slapton Sands were forced to abandon their homes without being told why ahead of the training mission
The extent of the tragic loss is illustrated effectively by the boot prints that remind us of the hundreds of men who gave up their lives while preparing to fight
More than 1,200 Allied soldiers were killed over two days off Slapton Sands in Devon, a disaster that was kept hidden by the authorities for decades. On April 27, 1944 over 400 of them were slaughtered by the friendly fire of shells bursts on the beach due to a timing error
The following day nine German E-boats passing through Lyme Bay stumbled upon the exercise and opened fire on the mock-invasion fleet, killing 749 men. Scores of bodies washed up on to the beach in harrowing scenes that would be replicated six weeks later on the beaches of Normandy
The survivors of Exercise Tiger were sworn to secrecy as the tragedy had to remain out of the public domain so not compromise the impending D-Day landings
General Eisenhower wanted live ammunition used during the training operation so troops would know the sound when they stormed the Normandy beaches a few months later
Mr Barraud also designed last year's There But Not There campaign, which placed silhouettes of First World War 'Tommy' troops across the UK, to mark the centenary of the end of the war.
He said: 'Last year our Tommy campaign captured the hearts of the nation, whilst giving a substantial boost to the mental health and wellbeing of veterans across the UK.
'A year on and we're hoping the great British public will get behind our D-Day 75 campaign by purchasing their own Bootprints to mark the great sacrifice of our WW2 heroes, in particular those who helped kick-start the liberation of Europe with the invasion of Normandy on D-Day.'
Details of the horrors have slowly come to light over the intervening decades. However, far less is still known about an appalling 'friendly fire' incident which the US authorities have never officially recognised
Schools, businesses and communities will be able to purchase commemorative D-Day Bootprints vinyls for £4 each, to be placed in public spaces nationwide
Eisenhower wanted the training missions to be as realistic as possible, although this led to problems when the delayed start of landings was not communicated naval officers planning an artillery barrage. As a result, troops arriving in landing craft, file photograph, were attacked by naval guns
Survivors of the friendly fire incident were ordered to remain silent because military officials did not want details of the blunder to be made public
The servicemen were killed in Operation Tiger which was a training operation ahead of the D-Day invasion of Normandy
The Exercise Tiger incident was only nominally reported afterwards because of the strict secrecy of the D-Day landings.
Pam Wills, 85, from Devon, was just 10 when Exercise Tiger took place near her home, and her family was evacuated before the exercise began.
She said: 'The US soldiers came over and talked to us, they gave us sweets and comics, but they then suddenly disappeared.
'We didn't know Exercise Tiger had taken place, but my father, who was in the Royal Observer Corps watching for enemy aircraft, saw ambulances going to and from Slapton Sands, so we knew something was wrong.'
Woody Johnson, the United States Ambassador to the United Kingdom, praised the soldiers who died during the exercise.
The British government set up a training ground around Slapton Sands on the coast of south east Devon, in late 1943 for the US forces. The location was chosen because of its similarities to Utah beach, where the Americans would be landing in Normandy
The victims of the tragedy, who were not acknowledged at the time of the incidents, were later commemorated at this memorial at Slapton Sands in Devon
He said: 'For a long time, many people had no idea that so many hundreds of American servicemen lost their lives on the coast of Slapton Sands as they rehearsed for the D-Day landings.
'Those men did not die in vain.
'Their sacrifices paved the way for their comrades to succeed on the beaches of Normandy and begin the liberation of Europe from Nazi tyranny.'
The disastrous exercise took place early on 28 April 1944 when eight tank landing ships, full of US servicemen and military equipment, converged in Lyme Bay near Slapton Sands.
However, a group of German E-Boats were alerted to the convoy and torpedoed the slow-moving ships.
With no British Navy destroyer to escort the American GIs, the consequences were catastrophic, with the final death toll considerably more than the number who died storming Utah beach in Normandy.
Among the dead was Sergeant Louis Archer Bolton, a 19-year-old newlywed from Iowa.
He was in the tank deck on board LST 531, when it took a direct hit by two torpedoes. His body was never recovered.
His niece, Laurie Bolton, will be among those at the event. She said: 'My uncle was in the US Army, 607th Graves Registration Company, 1st Platoon.
Artist Martin Barraud helps lay down 749 foot prints in the sand
Commemorative Bootprints plaques made by veterans will be available for £29.99, with each representing one of the 22,763 British and Commonwealth servicemen and women who were killed on D-Day and during the Battle of Normandy in the summer of 1944
The bootprint installation is the brainchild of Martin Barraud, the artist behind last year's 'There But Not There' campaign to mark the centenary of the end of WW1
'His platoon of 19 men was attached to the 3206th Quartermaster Service Company, and was going to be in charge of burying the dead on Utah Beach on D-Day.
'Only five men from his platoon survived Exercise Tiger. He was just 19 years old when he died and a newlywed, only having been married for just under a year. I was born on his birthday eight years after he died.'
The bootprint installation is the brainchild of Martin Barraud, the artist behind last year's 'There But Not There' campaign to mark the centenary of the end of WW1.
Commemorative bootprint plaques, made by veterans, can be bought for £29.99 with money raised from the campaign going towards programmes supporting veteran employment projects.
General Dwight D. Eisenhower wanted his men to be battle-hardened ahead of D-Day so he insisted on live ammunition being used during the trial run
American authorities acknowledged the E-boat incident in 1954 but they still refuse to accept what happened the day before when troops were killed by friendly fire during the botched training exercise. Pictured: Medics on the beach at Normandy
Each of these plaques represents one of the 22,763 British and Commonwealth servicemen and women who were killed on D-Day and during the Battle of Normandy in the summer of 1944.
Martin, who is chair of 'There But Not There', said: 'These plaques are made by veterans, to commemorate the veterans of 75 years ago and will help support the veterans of today, back into employment.
'Last year our Tommy campaign captured the hearts of the nation, whilst giving a boost to the mental health and wellbeing of veterans across the UK.
'A year on and we're hoping the Great British public will get behind our D-Day 75 campaign by purchasing their own bootprints to mark the great sacrifice of our WW2 heroes, in particular those who helped kick-start the liberation of Europe with the invasion of Normandy on D-Day.'
Associate professor Harry Bennett, a historian from Plymouth University, added: 'There were losses day in, day out, whether it was in Africa, down at Plymouth, on the Eastern Front, in the Northern Atlantic. The drip, drip, drip of lives being lost was enormous.
'Exercise Tiger was a terrible event with 749 deaths and it gets lost in history.
The first practice assault took place on the morning of April 27. Several of the landing ships were delayed so the American Admiral Don Moon decided to put back the assault on the beach until 8.30am. However, shockingly, some of the other landing ships were not informed of this schedule change and arrived at the beach at the previously agreed time of 7.30am. As a result, the artillery barrage which was meant to be fired before the practice invasion to recreate the sounds and smells of a naval bombardment was actually unleashed on disembarking American troops
'With Tiger you had 749 people whose lives were washed away and this installation gets people to think about something in a different way.
'Any new means which encourages the public to think about what happened to previous generations, to ordinary people is a good thing.'
Schools, businesses and communities will be able to purchase commemorative D-Day Bootprints vinyls for £4 each, to be placed in public spaces nationwide.
Commemorative Bootprints plaques made by veterans will also be available for £29.99, with each representing one of the 22,763 British and Commonwealth servicemen and women who were killed on D-Day and during the Battle of Normandy in the summer of 1944.
Mr Barraud said: 'Our enduring hope is that every one of the US, British and Commonwealth soldiers, sailors and airmen who gave their lives will have a Bootprint purchased in their memory.'