The ingenious technology that transformed battlefield tactics and helped the Allies win D-Day

Scarred by the Gallipoli campaign he initiated during the First World War, Winston Churchill well understood the risks of amphibious landings and the excruciating cost of failure.

Though the defences of Hitler’s ‘Atlantic Wall’ focused on major ports such as Cherbourg and Le Havre, the intermediate coastlines were also strongly protected by reinforced concrete pillboxes and shore batteries.

Furthermore, the beaches were laced with steel barriers – many of which were mined – designed to block landing craft from coming ashore. All such obstacles were covered by machine gun, mortar and artillery fire.

For the Normandy landings to be a triumph, the Channel would have to be crossed, beach obstacles surmounted, key points neutralised and urban areas penetrated. Forces amassed ashore would need to resupply and repair, and casualties would require treatment and evacuation.

Such were the special demands of the campaign that it would require a suite of novel military means.

But the artful and imaginative combination of engineering, science and military technologies helped transform battlefield tactics and campaign logistics. Never before, and arguably never since, had so much ingenious preparation paved the way for such a climactic battle with so profound an outcome.

Airborne forces

Parachute and glider-borne forces, already in use by the Germans and Russians, were a novelty for the British. In June 1940, Churchill commissioned the Army to “raise a corps of at least 5,000 parachute troops, suitably organised and equipped”.

Major John Rock of the Royal Engineers persuaded Churchill of the case for glider-borne forces to complement these parachutists, and himself formed the glider pilot regiment. Several parachute and airlanding brigades were formed, grouped into two divisions.

One of these, the 6th Airborne Division under Major General Richard Gale, landed from the air late on 5 June 1944 to secure the left flank of the Allied landings, including the seizure of key bridges on the Orne canal with pinpoint landings by glider.

Simultaneously, two American airborne divisions landed on the right flank of Operation Overlord at the southern end of the Cotentin peninsula.

Field Marshal Erwin Rommel, commander of the German forces in northern France, had devoted his attention to the threat posed by Allied parachute and glider-borne forces.

His solution was to order the erection of nearly a million wooden poles to render the likely landing grounds unusable. Described as “Rommel’s Asparagus”, this simple innovation not only hindered Allied airborne operations, but also allowed enterprising German infantry to incorporate the timber in building field defences.

In the round, however, Allied airborne forces played decisive roles by neutralising key threats to the landings, such as the Merville Battery, securing key points before the Germans could react, such as Pegasus Bridge, and holding the flanks against German counter attacks.

Hobart’s Funnies

Experience from the Western Desert and lessons from the disastrous raid at Dieppe in August 1942, in which the Canadians had taken heavy losses, inspired the British Army to invent a collection of specialist vehicles to deal with obstacles and strong points for the beach assault and for the fight inland.

This responsibility fell to Major General Percy Hobart, a former Sapper officer who had commanded 7th Armoured Division, the Desert Rats, in North Africa. Known as “Hobart’s Funnies”, these vehicles were grouped in the 79th Armoured Division and were the first vehicles on D-Day to assault up the beaches and penetrate the Atlantic Wall.

• The Crocodile was a flamethrower carrying 400 gallons of fuel that could project flame over 100 metres at trenches, bunkers and fortifications – with terrifying psychological effect.

• The Assault Vehicle Royal Engineers, known as the AVRE, fired a 40-pound high explosive ‘dustbin’ charge a distance of 150 yards. It could be fitted with fascines or small bridges to breach ditches and tank obstacles, mine ploughs to open routes through minefields. Its crew of six could dismount to place demolition charges or prepare obstacles.

• The ARK was a Churchill chassis with ramps fore and aft that other tanks could drive over to breach obstacles and small rivers.

• The Duplex Drive Sherman tank, an American innovation with a watertight canvas screen, could propel itself on to a beach from a landing craft several miles offshore. These were used in the initial assault to support the first waves of infantry.

Mulberry Harbours

The Dieppe raid had crystallised the realisation that the Allies could not rely on capturing a French port. And if ports could not be captured, the Allies would take ports with them.

Churchill gave a powerful stimulus to various engineer study teams who had been investigating how to repair, or even to replace, ports in liberated Europe, directing famously that “piers for use on beaches” must “float up and down with the tide. The anchor problem must be mastered. Let us have the best solution worked out. Don’t argue the matter. The difficulties will argue for themselves.”

Thus two artificial floating “Mulberry harbours” were developed to provide the port facilities necessary to offload the thousands of men and vehicles, and tons of supplies necessary to sustain the landings and the battle for Normandy.

The required capacity was 12,000 tons per day. The harbours were comprised of piers, breakwaters and ten miles of floating roadways, constructed by major civil engineering companies in dockyards around the British coast.

They required 600,000 tons of concrete. The purpose of these items was so secret that some of the construction force, not realising the products were for the war effort, went on strike and jeopardised their timely delivery.

The Mulberries were successfully towed into position on D-Day and were operational within a few days. On 19 June, a Force 8 storm blew into Normandy and destroyed the Mulberry harbour at Omaha Beach.

The harbour at Arromanches was better protected, and it survived – and came to be known as Port Winston. In the ten months after D-Day, it was used to land over 2.5 million men, 500,000 vehicles and 4 million tons of supplies.

The harbours astonished the Germans. Hitler’s henchman Albert Speer concluded: “By means of a single, brilliant technical idea, the enemy bypassed [our] defences within two weeks after the first landing. Our whole plan of defence had proved irrelevant.”

This remarkable feat of military engineering is one of the greatest ever, both in terms of its technical prowess and its strategic impact. The remains of the harbour are still visible today from the beaches at Arromanches.

Pluto

Another brilliant invention were the pipelines under the ocean – or “Pluto” – that delivered fuel to the Allied forces ashore.

Although the battle of Normandy was largely won by the time the first petrol was pumped to France, cross-Channel pipelines provided a significant supply of fuel for the remainder of the campaign.

This new technology would also provide the foundation for post-war offshore oilfield exploitation.

An edited version of this article first appeared in Boisdale Life magazine (boisdalelife.com). General Sir Peter Wall GCB CBE DL FREng is a former Chief of the General Staff, the professional head of the British Army. Major General Mungo Melvin CB OBE is author of Manstein: Hitler’s Greatest General and Sevastopol’s Wars: Crimea from Potemkin to Putin.