Exercise Tiger: The Disastrous Rehearsal for D-Day

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Podcast Transcript

The Allied invasion of Normandy was one of the most complex military operations ever conducted. Thousands of ships and planes had to work in conjunction with tens of thousands of soldiers who had to do one of the most difficult things in warfare: an amphibious landing. 

In addition to all of the planning that went into the invasion, there were many unknowns. The only way to learn was to practice some of the elements of the landing. 

In April 1944, about six weeks before D-Day, the Allies conducted a practice exercise off the coast of England, and it turned into one of the biggest disasters of the war.

Learn more about Exercise Tiger and the disastrous rehearsal for D-Day on this episode of Everything Everywhere Daily.


When we tell the story of D-Day, we think back with the benefit of hindsight. We know how everything worked out.

The Allies landed, had some initial setbacks, but eventually broke through and opened up a second front in the war, which helped liberate Western Europe and defeat Nazi Germany.

However, going into D-Day, there was a great deal of doubt about the operation’s success. 

There had never been an amphibious landing of this scale before. There had never been an airborne assault of this scale before. 

The Allies didn’t know what the weather would be, the exact state of the beaches they would be landing on, and how reinforced that section of the German Atlantic wall would be. 

Many of those things could only be discovered on the day of the invasion. 

Other things, however, could be practiced beforehand. 

In the months and weeks before D-Day, the Allies conducted a series of training exercises off the southern coast of England. 

In 1943, the British government set up an area that was to be used for the training of Force U. Force U was to be the group that would land at Utah Beach.

The area was known as Slapton Sands in Devon. Over 3,000 locals had to be evacuated both for security and safety, as live ammunition would be used in some of the exercises. 

Slapton Sands was selected because it was similar to Utah Beach, where they would be landing, as it had a gravel beach.

The idea behind the training exercise was sound. You don’t want to conduct one of the most important military operations of the war with thousands of troops that had never had to do an amphibious landing before. 

Certain things can only be learned by doing, especially because many of the ships that would be used, the LSTs or landing ship tanks, were relatively new designs built during the war. 

Before I get into the specifics of Exercise Tiger, I should note that most training exercises for D-Day were conducted without incident. Practice landings actually began as early as December 1943.

Exercise Tiger was to be a practice landing with troops from the US Army’s 1st Engineer Special Brigade, the 4th Infantry Division, and a smattering of other units. It was to be one of the biggest exercises in the lead-up to D-Day. 

Exercise Tiger was scheduled to take place from April 22 to April 30, 1944. 23,000 units that were to participate in D-Day were spread at assembly points all over southern England. They were to assemble and load their ships just as they would on D-Day. 

The first practice landing on the beach took place on the morning of April 27. 

While this practice landing isn’t the core of this episode, it had its own disastrous problems. 

General Eisenhower wanted the rehearsal landings to be as realistic as possible. As such, the ships would fire live rounds on the beach before the landing and over the soldiers’ heads as they approached shore. 

The landing was scheduled to take place at 7:30 am. However, several of the LSTs were late leaving port, so the admiral in charge of the operation, Don Moon, decided to delay the landing until 8:30. 

However, not all of the landing craft were informed of the change because their radios were operating on different frequencies, so they started their landings at the original 7:30 a.m. 

The plan was for the landing to take place one hour after the naval bombardment.

The British naval ships that were to fire the live round at the updated time accidentally ended up firing on the soldiers who were landing at the original time. 

110 American soldiers were killed by friendly fire. 

You can find varying estimates for the number killed. I’ve read estimates as high as 600. One of the reasons for the confusion is that the incident wasn’t disclosed to the press or the public because of the secrecy before D-Day. 

However, research conducted after the war conclusively put the number at 110. Most of those killed came from a single company that landed just three minutes before the barrage began.

This, however, was not the worst thing that was going to happen during Exercise Tiger. An even worse incident was to take place in less than 24 hours. 

Despite the friendly fire incident the exercise continuted. That evening, April 27, a group of ships which was dubbed Convoy T-4, which included eight LSTs were packed with soldiers, mostly from the US Army 1st Engineer Special Brigade. 

I should explain exactly what the LSTs were. 

Landing Ship, Tanks (LSTs) were an amphibious warfare ships used extensively during World War II. These vessels were designed to transport large numbers of vehicles, troops, and equipment directly onto shore without the need for docks or piers. 

Each LST was about 328 feet or 100 meters long and could travel at a speed of about 10 knots. They could carry up to 20 Sherman tanks or around 2,100 tons of cargo, along with hundreds of troops.

These were significantly larger than the Landing Craft, Vehicles and Personnel or LCVPs, which could carry about 36 infantry and appear in most movies about D-Day. 

The LSTs were much larger amphibious vessels that arrived on the beaches after the first waves landed. 

LSTs were used in the Pacific in the Solomon Islands as well as in Europe in the invasions of Sicily, the Italian Peninsula, Normandy, and Southern France.

So when Convoy T-4 set out on the evening of April 27, these large LST’s were filled with hundreds of soldiers each.

There were problems right from the start. The Allies only assigned two ships to protect the entire convoy and one of them didn’t show up because it had hit an LST earlier that evening and went to port for repairs.

That left the HMS Azalea, a small corvette, as the only protection for the convoy that night. The other ship that wasn’t present was a much larger destroyer, the HMS Scimitar. 

Not long after midnight April 28, six e-boats of the German 5th E-Boat Flotilla came across the ships. 

Here, I should explain what e-boats are because most people are probably unfamiliar with them. 

In German, they were known as Schnellboote, which simply means “fast boats.” 

The term “E-Boat” was an Allied designation for the boats created by the British. The “E’ simply stood for “enemy”. The Germans called them “S” boats.

E-boats, with a sleek, streamlined hull, were designed for speed and maneuverability. They could reach speeds of up to 43 knots (about 80 km/h or 50 mph), making them among the fastest naval vessels of the time.

E-boats were typically armed with torpedoes, making them deadly against larger ships. Their American equivalent was the PT boat.

Much of the German naval defenses in the Atlantic were E-Boats because they were fast, cheap, and effective. 

Several days earlier, on April 25, German reconnaissance planes flew past the Southern Coast of England. They saw the military build-up that was taking place, but they didn’t know what its purpose of it was. 

Word was sent to the German navy to watch for activity off the coast of Devon. 


On the morning of April 28, the Germans didn’t know what was going on or that the Allies were rehearsing for the invasion of France. They just saw some easy targets in Lyme Bay. 

The commander of the German ships, Bernd Klug, ordered his six ships to split up into three groups of two. 

The British had actually seen the ships from a distance. However, just as what happened just the previous morning, the British and American ships were using different radio frequencies. Moreover, word was sent to the HMS Azalea, who was ordered to do nothing and did not want to draw attention to the convoy. 

A little after 1:30 am, the German e-boats attacked, opening up with their guns, using tracer rounds at night. 

A little after 2 am, things became chaotic. 

A torpedo hit LST-507, and one of the e-boats actually careened into it. This caused an explosion and a fire on board the LST. Men began jumping overboard to avoid the fire into the cold waters of the Atlantic. 

One of the problems with the fire is that the trucks that were loaded on to the LST were all filled with fuel, again, to keep conditions similar to what they would experience on D-Day.  As the first spread, the fuel from all of the vehicles began to burn. 

Soon after, two torpedoes hit LST-531, and another torpedo hit LST-289.

LST-496 began using what little defenses it had to fire, but in the process, it ended up hitting LST-511 with friendly fire. 

By 3:30 a.m., the Battle of Lyme Bay was over. LST 507 and 531 were both sunk within minutes of being hit.  

202 men were lost on LST-507 and 424 were lost on LST-531. 

The rest of the ships that were hit managed to limp back home with some fatalities. 

In total, from the torpedo attacks and the friendly fire incident earlier in the day, in less than 24 hours, Exercise Tiger witnessed the loss of 749 American Servicemen. 

Because of the operation’s secrecy, the entire incident was unknown until it became public in the 1960s.

There were enormous implications that came out of the disaster of April 27 and 28.

For starters, there were ten American commanders who were lost, had top-level clearance and knew the plans for the invasion. If they had been captured, the entire operation would have been put on hold. Eisenhower ordered the bodies of the ten men to be found to ensure that they weren’t captured and could jeopardize the operation.

Radio frequencies were standardized before D-Day, so there wouldn’t be a repeat of errors from Exercise Tiger. 

Better life preserver training was given to the soldiers that would be in the amphibious craft, and small boats were assigned to pick up soldiers in the water during the landing. 

They also increased the aerial and naval bombardment of Cherbourg, where the German fleet in Normandy was headquartered, in an attempt to destroy as many E-boats as possible before the landings started. 

In one of the most ironic twists of the entire episode, the men involved in the exercises were part of Force U who were to land on Utah Beach. On D-Day there were only 197 casualties on Utah Beach, meaning that the losses from Exercise Tiger for Force U exceeded the D-Day losses by over threefold. 

Because of the operation’s secrecy, nothing was done to honor those who died after the war. It wasn’t until much later that memorials were erected in their honor. 

A Devon resident named Ken Small took it upon himself to create a memorial near Slapton Sands. 

There is a plaque in Arlington National Cemetery and also one on Utah Beach in France. There are additional memorials in the towns of Mexico, Missouri, and New Bedford, Massachusetts.

Exercise Tiger is a significant, though tragic, episode in the lead-up to D-Day, highlighting the immense challenges and the steep cost of preparing for one of the most critical operations of World War II.

While it was a costly lesson, from the events of Exercise Tiger, the Allies were able to modify their plans for the invasion of Normandy, which may have saved the lives of hundreds.