Rehearsals for D-Day taking place in Lyme Bay as part of Exercise Tiger

A rehearsal for the D-Day landings which resulted in the deaths of 749 American servicemen could have been far more devastating and might potentially have changed the shape of D-Day, according to new research.

As has been known since the 1980s, Exercise Tiger was taking place in Lyme Bay – off the coast of South Devon and Dorset – in late April 1944 when a convoy of United States Navy ships was attacked by heavily-armed German motor torpedo boats (S-Boats).

In an attack lasting less than 60 minutes, three allied vessels were torpedoed – with two of them subsequently sinking – resulting in an official death toll of 551 United States Army and 198 United States Navy personnel.

However, new research based on eyewitness accounts and official military records has shown the death toll could have been far greater because a second group of allied invasion ships – making its way along the English Channel – narrowly avoided becoming embroiled in the disaster.

If that had happened, it could have resulted in an even greater loss of life and the destruction of several tank landing ships (LSTs) essential to the planned Normandy invasion.

The findings are the result of an investigation by Dr Harry Bennett, Associate Professor of History at the University of Plymouth. They will be revealed in greater detail as part of FUTURES2020, a virtual festival of discovery taking place on November 27 and 28.

He believes such a loss, in terms of both lives and vessels, would have left allied planners with a serious headache – facing a shortage of the highly specialised LSTs vital to D-Day, worried about the damage to the morale of Allied forces and desperately concerned about the potential for German S-Boats to cause havoc on D-Day.

Ultimately, it could have led Allied planners to alter their plans for D-Day.

Dr Harry Bennett
Associate Professor of History Dr Harry Bennett

Dr Bennett, an expert in maritime and military operations during World War Two, said:

“Exercise Tiger is already one of the more tragic stories of the war. It went largely unreported at the time because the allied commanders didn’t want to give away details of tragedy.
"It finally became more common knowledge in the 1980s, but these new findings show for the first time that less than 30 minutes after three American ships had been torpedoed to devastating effect a second incident occurred in which forces of three of the world’s most powerful wartime navies stumbled upon each other in mid-Channel only narrowly avoiding a pitched battle.”

The near-miss only came to light after Dr Bennett was involved in a service over the wreck sites for the two sunken LSTs, attended by the families of those involved in Exercise Tiger.

He posted about it on social media and was subsequently contacted by the family of a US naval serviceman, Ensign William H Hogan, who was serving in the UK in 1944. The family provided transcripts of official records that helped to establish what happened that night.

Those records show that on the night of April 27-28 1944, Hogan’s ship – LST 51 – was part of a convoy codenamed Obstacle making its way from Falmouth in Cornwall to Portland on the Dorset coast.

As they sailed towards Lyme Bay, they saw flashes in the sky from the action to the North where the Exercise Tiger T4 convoy of LSTs was coming under attack by nine German S-Boats that had sailed from Northern France late on 27 April to look for allied shipping in Lyme Bay.

Ensign William H Hogan in his uniform (Credit Hogan Family)
Ensign William H Hogan in his uniform (Credit Hogan Family)
LST 51 loading at Portland Harbour ahead of the D-Day landings (Credit Hogan Family)
LST 51 loading at Portland Harbour ahead of the D-Day landings (Credit Hogan Family)

By analysing official records kept by the US, British and German navies, Dr Bennett was able to correlate each ship’s position in the Channel and discovered that as the Germans made their escape from the attack on the T4 convoy they were pursued and eventually fired upon by the British destroyers.

In their flight to the south the German S-Boats and British destroyers converged, with the British opening fire, at exactly the point when they met the Obstacle convoy heading towards Portland. In brief moments of confusion the British destroyers opened fire towards the Obstacle convoy thinking that the dark shadows of the ships were the Germans.

A potential friendly fire attack was swiftly averted with no damage done, but not before the Germans had successfully fled the scene heading back to Northern France, leaving the allied forces to count their costs.

Dr Bennett said:

“Ironically the tenacity and ferocity shown by British forces perhaps prevented an even bigger tragedy that night. Running slap bang into a second convoy on their run home the German S-Boats, if they had torpedoes remaining, might have been in a position to inflict serious damage. The Nelsonian tradition of “engage the enemy more closely” and get stuck in meant that the S-Boats were not about to hang around that night.

“The nine S-Boats at sea that night carried between them 36 torpedoes. Perhaps only five found their targets as a result of good fortune and professionalism on the part of the United States and Royal Navies. The potential for the tragedy of Exercise Tiger that night to have assumed even bigger proportions is obvious.”

FUTURES2020 will see the University of Plymouth joining forces with the universities of Bath, Bristol, Exeter and Bath Spa to offer the public the opportunity to meet and chat with researchers, and take part in activities that showcase the innovative research taking place in their cities. To find out more about the range of activities taking place, visit our event page.

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