D-Day 70th Anniversary: Training, Logistics, Build-up, Deception

By Gavin Greenwood | 02 June 2004 | Updated: 04 June 2014

We continue our series of features and trails exploring the Normandy landings with a closer look at locations and collections in England and explain how the Allies amassed and trained an army of millions.

a photo of a group of men listening to an officer
Men of 4 Commando, 1st Special Service Brigade, being briefed by Lt Col R Dawson just before embarking for Normandy, June 1944.© IWM (B 5098)

Planning and Preparation

During 1943 and 1944 planning and preparation for Overlord gathered pace in Britain and the United States.

By mid-1943 the U-boat threat to Allied merchant shipping in the Atlantic had been largely countered by increasingly effective air patrols, technological developments and the deciphering of German naval Enigma codes that enabled convoys to be routed.

The success of the invasion also hinged on timing. Calm weather was seen as essential for the assault wave, which would depend on many small craft and inherently unstable equipment such as swimming tanks. A low Spring tide was vital to expose as many of the German beach obstacles as possible and at least a clear half moon was necessary for the parachute drops.

Shows a concrete pillox sat in an empty field on a clifftop.

Photo: by 1944 the south coast of England was littered with pill boxes and fortifications - such as this one still standing today at Ringstead in Dorset. Photo by kind permission of www.weymouth-dorset.co.uk

Due to training schedules in the US and the availability of shipping the date had to be after 1st June. This gave five dates during the month: between 5th-7th June and the 19th-20th.

Eisenhower decided on 5th June, with H-Hour for the sea-borne assault timed for dawn, or around 0630. The initial parachute drop would begin shortly after midnight, followed by successive waves of reinforcements.


Shows a photo of a panel in the Overlord embroidery, depicting General Eisenhower, in khaki uniform, inspecting a number of soldiers in khaki uniforms and helmets.

Photo: General Eisenhower as depicted in the Overlord Embroidery. Picture courtesy: D-Day Museum.

In late 1943 Eisenhower was appointed Allied commander for the European theatre and in early 1944 joined Supreme Headquarters Allied Expeditionary Force (SHAEF) in London.

SHAEF’s command structure devolved from four senior British and two US officers, including Eisenhower.

They included Air-Chief Marshall Tedder as Deputy Supreme Commander, Adm. Ramsay in command of the Allied Naval Expeditionary Force, Air-Vice Marshall Leigh-Mallory in command of the Allied Expeditionary Air Force while Gen. Montgomery was given command of the 21st Army Group, comprising the 1st US Army and the British 2nd Army.

Shows a photograph of a front room with armchairs and a coffee table scattered around, on the wall behind is a huge map of the south coast of the UK.

Photo: the inside of Southwick House has been preserved as it was in 1944. The map on the wall is the actual map used during the invasion of Europe and is set to the position it was at on 6 June 1944. Picture courtesy: Southwick House.

As D-Day grew ever closer General Dwight D. Eisenhower moved his general HQ to Southwick House in Hampshire. You can still visit the house today by appointment (book through D-Day Museum).

The Build-up

The first US military formation (4,500 men from the 34th Division) arrived in Northern Ireland in mid-January 1942. Under a programme codenamed Bolero, within two and half years more than 1.5 million US military personnel had arrived in the UK - around 700,000 between January-June 1944 alone - and were scattered in thousands of camps and air bases across the country.

On 6th June 1944 more than 5 per cent of this total landed in France. Within the next six months almost all US ground troops had left Britain for mainland Europe.

The British Army over the same period doubled from its 1940 strength of 1.5 million men. In addition more than 250,000 Canadian troops were in Britain, as were many thousands of French, Polish, Dutch, Belgian and Czech personnel deployed in national contingents.

Shows a black and white photograph of a woman hanging out her laundry in her back garden. There is a man and a woman doing some gardening. On the other side of the garden wall, in the street, there are lots of army tanks lined up.

Photo: southern England eventually resembled a vast military camp. Here American Howitzer teams clutter the streets of Southampton. Picture courtesy: Imperial War Museum.

The amount of supplies required to sustain, arm and equip this huge number of troops was immense. Much of what was needed to outfit, feed, and arm millions of soldiers, sailors and airmen was shipped across the Atlantic.

The invasion and follow-on forces required 16 million tonnes of supplies, 4,200 tanks and other tracked vehicles, 3,500 artillery pieces, 140,000 transport vehicles and 12,000 aircraft.

shows a memorial consisting of an obelisk on a concrete base. It is situated in a street - across the street cars are parked in front of buildings.

Photo: throughout the southern English ports you can find memorials commemorating the D-Day build up and landings - such as this American War Memorial on Weymouth Esplanade. Photo by kind permission of www.weymouth-dorset.co.uk

Further, thousands of specialised landing craft had to be gathered in British ports from the US, where most were built, or from the Mediterranean. Less than a month before D-Day, almost 2.88 million Allied troops were encamped in southern England.

Shows a black and white photo of tanks lined up in a residential street on Portsmouth seafront.

Photo: Tanks in the restricted zone of Portsmouth seafront. Picture courtesy: Bovington Tank Museum.

In August, 1943, Southsea seafront was declared a restricted zone and by 1st April, 1944 Portsmouth became part of the coastal strip, from the Wash to Land's End, closed to all visitors. You can learn about this history as well as more about the D-Day landings by visiting the excellent D-Day Museum at Southsea.


Training this huge and complex force was undertaken at all levels of command. While assault infantry, armoured and airborne units could prepare for the invasion at company or squadron, battalion or regimental levels – naval, air and army support units required larger scale exercises to test their abilities to operate in larger groups.

Shows a black and white photo of two soldiers on a landing craft deck. One soldier is wearing a kind of life jacket with a mouth-piece for breathing underwater.

Photo: on the deck of a landing craft, a soldier demonstrates underwater escape apparatus issued to D-Day tank crews. Photo courtesy of Bovington Tank Museum.

As expected, the first large training exercises - on the south Devon coast at Slapton Sands – revealed communications problems, lack of mission comprehension, poor crisis management abilities and a general sense of chaos.

While successive and more complex manoeuvres over the next few months addressed many of these problems, the intensity of training, the lack of experience among many personnel and the often exceptionally dangerous nature of the equipment developed to support the landings led to a high number of deaths and injuries among the troops.

A dramatic and somewhat puzzling trace left by this vast army can be found at Hankley Common, between Elstead and Tilford in Surrey. Built as training ground for soldiers preparing to attack Hiltler's 'Atlantic Wall'. Today it is an overgrown reminder of the preparations that went into the build up to D-Day.

Shows a photo of a section of a very thick wall, surrounded by trees.

Photo: The wall as it stands today, showing one of the breaches created by the Double Onion and damage from shellfire. © 2001 Chris Shepheard

To find out more about the Surrey Atlantic Wall visit the website by clicking on this link

The Germans, who in general did little to impede the build-up, demonstrated on one occasion just how hazardous the invasion could be. In late April 1944 a convoy of landing ships training at night off Slapton Sands was attacked by German E-boats.

Within a few minutes one of the landing ships had been sunk and another badly damaged. More than 750 US army and naval personnel were killed and a further 300 wounded in the swift attack - a casualty toll three times greater than among assault troops landing on Utah beach in Normandy barely six weeks later.

To find out more about the tragedy at Slapton Sands visit the website of the Exercise Tiger Association

Shows a black and white photo of a landing craft by the shore at Slapton. The number 323 is painted in white on the ship.

Photo: a landing craft at Slapton Sands. Today a Sherman tank - recovered from the sea in 1984 - stands as a reminder of the tragedy in April 1943. Picture courtesy: NavSource Online © Bill Brindley.

Along the coast from Slapton, the village of Tyneham in Dorset was also used as an Allied training ground.

In November 1943, the residents of Tyneham received a letter from a Major-General at the War Department. It read:

"It is regretted that, in the National Interest, it is necessary to move you from your homes, and everything possible will be done to help you, both by payment of compensation, and by finding other accommodation for you if you are unable to do so yourself."

Shows a photograph of a street in Tyneham. Semi-ruined buildings line the street and an old red phone box can be seen on the left of the photo.

Photo: Tyneham remains uninhabited to this day - a ghostly reminder of the impact of the D-Day build up. Photo by kind permission of www.weymouth-dorset.co.uk

The requisitioned village was never returned to its pre-war inhabitants and is still MOD land - accessible by the public only at weekends and on public holidays. A similar fate befell the village of Imber on Salisbury Plain, it remains to this day a deserted village - in the middle of a MOD firing range.


Shows a vast row of soldiers and tanks on a gently sloping grassy hill.

Photo: 1st Canadian Army Tank Brigade parade for the King on the South Downs February 1943. Logistics of fuel and supply posed a problem for the Allies. Picture courtesy: Gote House Publishing.

Although the Allied command recognised that they could successfully land a large force on the Normandy beaches with little serious interference from the Luftwaffe or the German navy, concerns remained over reinforcing and resupplying the units ashore.

Two Mulberry harbours – floating concrete sections that when joined together formed huge quays and cargo-handling platforms - were constructed for the US and the British beaches.

Absorbing some 2 million tonnes of concrete and steel, these artificial harbours were supported by a complex infrastructure of pier heads and floating roadways enclosed within a lagoon of specially constructed breakwaters and scuttled ships.

Shows a black and white photo of a man and a woman working with large metal shells. The man has an armband with the letter A on his left arm.

Photo: Munitions workers filling cartridges for D-Day. Picture courtesy: Explosion! Museum of Naval Firepower.

The other great challenge was moving the vast amount of fuel needed for the fighting and support vehicles into France. During the invasion phase, this was solved by pumping fuel ashore from tankers moored miles offshore, but a more permanent solution was offered by PLUTO, the acronym for Pipe Line Under The Ocean.

Pluto was based on four flexible 3-inch bore pipes, totalling nearly 300 miles, laid from specially adapted ships. US forces liberated and secured Cherbourg in late June and PLUTO was laid in a single 10-hour operation in July to be operational in August.

Once fully operational, PLUTO pumped thousands of gallons of petrol an hour under the Channel between carefully concealed pumping stations in the Isle of Wight and Cherbourg.

Deception and intelligence

Shows a photo of a machine resembling a typewriter in a wooden box.

Photo: the Enigma encoding device. Coded signals from these machines were sent to Nazi forces all over the world during WW2 and played a vital role in deception and intelligence during the build-up to D-Day. Picture courtesy: Imperial War Museum.

Preparations for the invasion were impossible to conceal and the major priority for the planners was to convince the Germans that the landings would not centre on Normandy.

This was achieved by a series of elaborate deception programmes, the ability to read German codes (Ultra), coupled with tight control over information related to D-Day and the movement of civilians around the south coast where invasion shipping was being assembled and the embarkation camps established.

Bletchley Park, the now-famous nerve-centre of Allied de-cryption, played a vital role in the preparation and deception operations leading up to D-Day.

Just prior to D-Day (6th June, 1944) the Enigma messages monitored by Huts 3 and 6 confirmed that the German High Command had followed false information that the Allies had stationed an army in Kent and were about to invade the Pas-de-Calais area, thereby forcing the enemy to keep Panzer divisions away from Normandy.

Shows a black and white photo of men and women working at a long desk.

Photo: Hut 3, 1943 - it took hundreds of codebreakers to laboriously decipher the signal traffic from German Enigma machines. Picture courtesy: Bletchley Park.

The Huts also helped on D-Day and just after to keep the General Eisenhower GHQ at Southwick informed of Allied progress, from the broken Enigma messages.

The Allied campaign to focus German anti-invasion preparations on the Pas-de-Calais area was conducted on a number of levels (Operation Bodyguard). The most elaborate was the creation of two ‘phantom’ armies that appeared poised to attack either Pas-de-Calais (Fortitude South) or Norway (Fortitude North).

While the Germans showed little sign of believing the Norway ruse, the entire military high command and Hitler believed that the First US Army Group (FUSAG), notionally commanded by General George Patton, was poised to strike across the Channel even after the D-Day landings had taken place in Normandy.

The Cabinet War Rooms, where Churchill famously led the country during the dark days of the Blitz, were also integral to D-Day deception plans. Here the London Control Section also worked on the Pas-de-Calais deception.

Shows a photo of a desk with an anglepoise lamp, papers and several small chests and boxes on it. There is a sepia coloured world map in the background.

Photo: the Cabinet War Rooms played a vital role in the Pas de Calais deception. Photo courtesy: Imperial War Museum.

The FUSAG deception involved the daily transmission of thousands of the routine signals communications that a large formation would generate. This was achieved by the deployment of hundreds of small signals units across southern and eastern England whose sole task was to send messages it was known the Germans would intercept and analyse.

In addition, captured and ‘turned’ enemy agents were used to send convincing intelligence to their German handlers, with their reports sometimes corroborated in fake news stories in the press.

Shows a photo of a white booklet marked with a red cross from corner to corner. Top Secret is written in red.

Photo: Top Secret minutes of a meeting held on 2nd June 1944, attended by General Eisenhower, Air Chief Marshal Tedder, Admiral Ramsay and General Montgomery. Picture courtesy: Imperial War Museum.

Apart from fascinating documents that tell the personal stories of the conflict, exhibits include the secret briefing documents written by Eisenhower, Montgomery and other commanders; top secret papers relating to the double-agent Garbo whose messages helped deceive the Nazis as well as sabotage equipment used by Special Operations agents.

The Imperial War Museum has a superb dedicated website to the D-Day 70th anniversary where you can find out exactly what there is relating to D-day in all of the IWM sites - from HMS Belfast to IWM Duxford, which has its own D-Day exhibition and trail in its Land Warfare Hall.

Air and naval preparations

Shows a photo of three planes with propellers, suspended from the ceiling. The one in the foreground is shiny and black.

Photo: Spitfire, Focke-Wulf 190 and Mustang at the Imperial War Museum, Lambeth. All three featured in the fight for the skies over Normandy. Photo courtesy: Imperial War Museum.

In order to prepare the ground for the invasion, the Allies also had to ensure the Luftwaffe and German navy could not interfere with the landings and that the German army’s ability to reinforce units in Normandy was severely restricted.

By early 1944 the Luftwaffe’s strength had been steadily reduced by a combination of Allied air attacks on German aircraft production and fuel targets, as well as huge losses taken by aircrew on both sides during the Allied bomber offensive against Germany.

At the Royal Airforce Museum, Hendon, you can see many of the key aircraft of the period.

Shows a photograph of the exterior of the Royal Air Force Museum framed by a Spitfire and a Hurricane aeroplane.

Photo: Outside the Royal Airforce Museum, Hendon. Stripes were painted on wings to identify Allied planes on D-Day. Photo courtesy: RAF Museum, Hendon.

Defence of Germany was the Luftwaffe’s main priority and with many of its specialised ground attack formations deployed on the Eastern Front against the Russians, by early 1944 only 400 German combat aircraft were stationed in France.

The Allies set out to further reduce this number, as well as to prevent German army reinforcements being switched from the Pas-de-Calais region and elsewhere in northern Europe to Normandy once it became clear that D-Day represented the main event and not a feint.

Tangmere Airfield in West Sussex was at the forefront of the effort to combat the Luftwaffe, providing an important base for fighter squadrons. 

Photo: volunteers run Tangmere Museum, many of whom were wartime RAF pilots, navigators and groundcrew. Picture courtesy: Tangmere Military Aviation Museum.

Under the Transportation Plan (February-June 1944) more than 11,000 Allied fighters and bombers carried out more than 200,000 sorties, or individual missions, against invasion-related targets.

Nearly 200,000 tonnes of bombs were dropped during the three-month campaign, most of them on the railway and road system, airfields, radar stations and other military targets such as artillery positions and bunkers of the Atlantic Wall.

In order not to indicate any area of specific interest, for each target bombed in the Normandy area two targets were attacked elsewhere.

Shows a black and white photo of one plane low in the air and another on the ground in a grassy field.

Photo: spitfires taking off from Normandy. Picture courtesy: IWM Duxford .

The Duxford 78th Fighter Group played an important role in D-Day and after. At Imperial War Museum of Aviation at Duxford, seven acres of indoor exhibition space include one of the finest collections of tanks and military vehicles in the country and a range of exhibitions, among them the recently opened Normandy Experience.

The Allied navies were also active in the Channel against German E-boats, U-boats and destroyers. In late April two running battles between Royal and Canadian Navy warships and German E-boats and destroyers resulted in losses on both sides.

Photo: HMS Belfast was at the forefront of the Navy's efforts to subdue the German beach defences on D-Day. Photo courtesy: Imperial War Museum.

From 20th May, a series of information panels around Portsmouth and its twinned city, Caen in France, will reveal the significance of various locations on D-Day. Walk the Story boards will offer information in English and French and a leaflet is available to accompany the trail. Also in Portsmouth, the Royal Naval Museum and the Historic Dockyard will hold special exhibits from 28th May to 6th June. For more information on these events and others in Portsmouth, click here.

The E-boat attack on the Tiger convoy at Slapton that killed more than 700 US army and navy personnel illustrated the threat German ships posed to the invasion fleet. However, after the April action there were no further serious German attempts to disrupt either the assembly of the invasion fleets or other training exercises.

By mid-May 1944 all the component elements for Overlord were largely in place and D-Day had ceased to be an exercise in planning and logistics, training and preparation.

Shows a photograph of two World Two veterans sitting side by side. They are wearing berets with military badges fixed to them and one has a row medals pinned to his jacket.

Photo: Nearly 3 million Allied troops took part in the air, sea and land attack that became the first step to liberating Europe from Hitler 60 years ago. Veterans will be attending commemorative events around the UK on 6th June. Picture courtesy: D-Day Museum.

For all those about to be involved in the greatest sea-borne invasion ever attempted, all that stood between them and the culmination of often years of training and preparation was the decision by the Allied political and military leaders to order the invasion - D-Day - to begin.

Read Gavin Greenwood's feature exploring the background to the D-Day landings

Read Gavin Greenwood’s feature about the Normandy Landings of June 6 1944

Explore some of the locations and museums in Normandy today that tell the story of D-Day

Read about the Mulberry Harbours and how they kept the supplies rolling after the D-Day landings

Read our feature on the different types of tank or Hobart's Funnies, developed for the D-Day landings

Read our timeline of events leading up to D-Day

Click here to explore D-Day web links

Additional research for this feature by Caroline Lewis.

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