In April 1941, when General Bernard Montgomery became commander of South-Eastern Command in the UK, he conducted the largest military exercise to date in the UK, Exercise Tiger, in May 1942, a combined forces operation involving 100,000 troops. Troops participating in Tiger noted that it was particularly gruelling for the infantry involved, who marched over 100 miles during the course of the exercise.
A second exercise by the same name was conducted in 1944; this was an eight-day practice run for theUtah Beach landings of the D-Day invasion. During the Exercise, an Allied convoy was attacked, resulting in the deaths of 749 American servicemen. 
In late 1943, as part of the war effort, the British Government evacuated approximately 3000 local residents in the area of Slapton, South Hams District of Devon. Some of them had never left their villages before.
Landing exercises had started in December 1943. Exercise Tiger was one of the larger exercises that would take place in April and May 1944. The make up of Slapton Beach was selected for its similarity to Utah Beach, namely a gravel beach, followed by a strip of land and then a lake.
The exercise was to last from 22 April until 30 April 1944, at the Slapton Sands beach. On board nine large Tank landing ships (LSTs), the 30,000 troops prepared for their mock beach landing.
Protection for the exercise area came from the Royal Navy. Two destroyers, three motor torpedo boatsand two motor gun boats patrolled the entrance to Lyme Bay and motor torpedo boats were watching theCherbourg area where German E-boats were based.
The first practice assaults took place on the morning of 27 April. These proceeded successfully, but early in the morning of 28 April, German E-boats that had left Cherbourg on patrol spotted a convoy of 8 LSTs carrying vehicles and combat engineers of the 1st Engineer Special Brigade in Lyme Bay and attacked. One of these E-Boats was S-130, now in dry dock in Plymouth, Devon. One transport caught fire and was abandoned, a second sank shortly after being torpedoed, a third was set on fire but eventually made it back to shore. The remaining ships and their escort fired back and the E-boats made no more attacks.
638 servicemen were killed, compared to only about 200 in the actual Utah Beach landing, 441 U.S. Army and 197 U.S. Navy personnel. Many servicemen drowned in the cold sea while waiting to be rescued. Soldiers unused to being at sea panicked and put on their lifebelts incorrectly. In some cases this meant that when they jumped into the water, the weight of their combat packs flipped them onto their backs, pushing their heads underwater and drowning them. Dale Rodman, who travelled on LST-507, commented "The worst memory I have is setting off in the lifeboat away from the sinking ship and watching bodies float by."
Of the two ships assigned to protect the convoy, only one was present. HMS Azalea, a corvette was leading the nine LSTs in a straight line, a formation which later drew criticism since it presented an easy target to the E-boats. The second boat which was supposed to be present,HMS Scimitar, a World War I destroyer, had checked into Plymouth for minor repairs. The American forces had not been told this. When other British ships sighted the E-boats earlier in the night and told the corvette, its commander failed to tell the LST convoy, assuming incorrectly that they had already been told. This did not happen because the LSTs and British naval headquarters were operating on different frequencies. Also, British shore batteries defending Salcombe Harbour had seen silhouettes of the E-boats but had been instructed to hold fire so the Germans would not find that Salcombe was defended.
When the remaining LSTs landed on Slapton Beach, the blunders continued and a further 308 men died from friendly fire. The British heavy cruiser HMS Hawkins shelled the beach with live ammunition, following an order made by General Dwight D. Eisenhower, the Supreme Allied Commander, who felt that the men must be hardened by exposure to real battle conditions. British marines on the boat recorded in its log book (the only log which has since been recovered from any of the boats) that men were being killed by friendly fire. "On the beaches they had a white tape line beyond which the Americans should not cross until the live firing had finished. But the Marines said they were going straight through the white tape line and getting blown up".
As a result of official embarrassment and concerns over possible leaks just prior to the real invasion, all survivors were sworn to secrecy by their superiors. Ten missing officers involved in the exercise had Bigot-level clearance for D-Day, meaning that they knew the invasion plans and could have compromised the invasion should they have been captured alive. As a result, the invasion was nearly called off until the bodies of all ten victims were found.
There is little information about how exactly individual soldiers and sailors died. Various eyewitness accounts detail hasty treatment of casualties and unmarked mass graves in Devon fields.
Several changes resulted from mistakes made in Exercise Tiger:
- Radio frequencies were standardised; the British escort vessels were late and out of position due to radio problems, and a signal of the E-boats' presence was not picked up by the LSTs.
- Better life vest training for landing troops.
- New plans for small craft to pick up floating survivors on D-Day.
The casualty statistics from Tiger were not released until August 1944 along with the casualties of the actual D-Day landings themselves.
There is still very little documentation in official histories about the tragedy. Some commentators have called it a cover-up, but the initial critical secrecy about Tiger may have merely resulted in longer-term quietness. In his book The Forgotten Dead - Why 946 American Servicemen Died Off The Coast Of Devon In 1944 - And The Man Who Discovered Their True Story, published in 1988, Ken Small declares that the event "was never covered up; it was 'conveniently forgotten'". Charles B. MacDonald, author and former deputy chief historian at the U.S. Army Center of Military History, notes that the incident was reported in a press release issued from the Supreme Headquarters, Allied Expeditionary Force, and appeared in the July issue of Stars and Stripes. In addition, the story was detailed in at least three books at the end of the war, including, Captain Harry C. Butcher 's My Three Years With Eisenhower (1946), and in several publications and speeches in the intervening years.MacDonald surmises that the press release went largely unnoticed in light of the larger events that were occurring at the time, the battle for France in the summer of 1944, and the fact that they were just glad that the war was over in 1945.
Memorials to the victims
With little or no support from the American or British armed forces for any venture to recover remains or dedicate a memorial to the incident, Devon resident and civilian Ken Small took on the task of seeking to commemorate the event, after discovering evidence of the aftermath washed up on the shore whilebeachcombing in the early 1970s.
In 1974, Small bought from the U.S. Government the rights to a submerged tank from the 70th Tank Battalion discovered by his search efforts. In 1984, with the aid of local residents and diving firms, he finally raised the tank, which now stands as a memorial to the incident. The local authority provided a plinth on the seafront to put the tank on, and erected a plaque in memory of the men killed. Small documents how the local villagers were of more assistance than either the US or UK military officials. Later the American military honored and supported him, when at the same time the UK military were snubbing his efforts. Small died of cancer in March 2004, a few weeks before the 60th anniversary of the Exercise Tiger incident.
In 2006, the Slapton Sands Memorial Tank Limited (a non-profit organization, one of whose directors is Small's son Dean) are seeking to establish a more prominent memorial listing the names of all the victims of the attacks on Exercise Tiger.
In popular culture
Exercise Tiger was relocated from Slapton to Bereton on the Devon coast and used as the background toKate Ellis's book, The Armada Boy, first published in 1999.
A radio play 'The Tank Man' by Julia Stoneham, describing Ken Small's efforts was broadcast on BBC Radio 4 on 24 October 2007. 
Exercise Tiger formed the basis of the last episode of the sixth (2008) series of the ITV drama Foyle's War.
Exercise Tiger features in Michael Morpurgo's book The Amazing Story of Adolphus Tips. Exercise Tiger. "The D-Day practice landing tragedies uncovered" by Richard T. Bass, published by Tommies Guides 2008. A comprehensive and in depth analysis of the events on April 28th 1944, presenting evidence supporting the detailed cover up of the event. Exercise Tiger provides a plot driver for the Jack Higgins novel Night of the Fox.