While the D-Day invasion of June 6, 1944 is one of the most well-known operations of World War II, much less is commonly known about the preparation that went into it.  In fact, the invasion was put on hold just weeks before its planned date as a direct result of a tragic training exercise – Exercise Tiger – designed to prepare troops for the landing at Normandy.

The shores of Slapton, England on the coast of the English Channel were picked as a dress rehearsal site for their similarity to the beaches of Normandy.  The rehearsal was scheduled to run from April 22-30, 1944 and included live fire drills as well as a realistic landing exercise.  Every aspect was designed to be as close to the real thing as possible – from the feel and look of the beaches, to the tactics, and even the smell of a beach landing with live munitions.  Unfortunately, the exercise became too real and by the end, 946 American servicemen were dead.

According to Robert  Gore-Langton, the first few days of the exercise went well with no major hiccups.  But on April 27, a group of nine German E-boats based out of Cherbourg, France spotted eight Allied LSTs traveling in a line (not a great formation for defense, by the way) in Lyme Bay not far from Slapton.  The LSTs were escorted by a single Royal Navy Corvette, the HMS Azalea.  Only one armed escort ship + traveling in a straight line = juicy opportunity for the German torpedo boats.

Some pictures for context:

The HMS Azalea, a Royal Navy Corvette typically used as an anti-submarine convoy escort

An American LST (Landing Ship, Tank), used to deliver troops, cargo, and vehicles directly to a beachA German E-Boat or torpedo boat, very fast and heavily armed

The casualties that ensued on the Allied side were the result of a perfect storm of factors.  The first major factor was communication, or lack thereof.  The American and British forces were communicating on different frequencies and when British forces spotted the German E-boats, they were unable to warn the American LSTs.  Second, there were several British defense batteries on shore, but they were ordered not to fire on the German boats so as not to reveal that the beach was defended.  Third, once the Germans began firing torpedoes, the Allied ships were ordered to scatter in order to avoid further damage.  Many men – who were poorly trained in how to use their flotation devices – jumped into the cold water where they were dragged under by their heavy gear and drowned.

American LST 289, which was damaged by a German torpedo during Exercise Tiger

The attack from the German E-boats would have been bad enough, but a lack of communication soon cost more American lives.  In keeping with Eisenhower’s desire to make this exercise as realistic as possible, several ships were placed in the bay and were directed to fire live rounds just beyond the shore line.  However, these ships and their planned artillery drills were delayed – a message that never got to the Americans, who began flooding ashore at their previously arranged time.  As they ran ashore, artillery from the ships began raining down and killed around 300 more troops.

In the end, 946 American troops were killed (which is more than were killed on Utah Beach in the actual invasion), several hundred were wounded, and the D-Day invasion was temporarily put on hold until ten men with intimate knowledge of the D-Day plans were located.  Despite the tragic events, valuable lessons were learned and some changes were made to ensure these mistakes wouldn’t happen again.  First and most importantly, communications were standardized between the British and American forces so that all parties had access to the information they needed.  Second, soldiers were given more thorough training on how to use their flotation devices in order to avoid unnecessary drowning casualties.  Lastly, small boats were to be deployed to pick up any soldiers who fell into the water.

Thanks to the lessons learned from the disaster of Exercise Tiger, the Allies went on to successfully invade Normandy and begin their march to Berlin.