The D-Day Invasion At Normandy May Not Have Succeeded Without The Mulberry Harbors

The D-Day Invasion At Normandy May Not Have Succeeded Without The Mulberry Harbors

The Mulberry artificial harbors proved a logistical wonder along the beaches of Normandy.

No Allied amphibious invasion in World War II left such a bitter legacy as Operation Jubilee, the ill-fated British-Canadian raid on the northern French port of Dieppe on Wednesday, August 19, 1942.

Despite partial successes to the west and the east, the main assault on the shingled beaches by 5,000 men of General Pip Roberts’s Canadian 2nd Infantry Division, 1,000 British Commandos met resistance far more fierce than expected. Many of the Canadians in the landing craft were casualties before they reached shore, and the troops and Churchill tanks that did land were pinned down by heavy German fire and blocked by obstacles. They never reached the town itself.

Almost none of the enemy installations marked for destruction was reached, and only a portion of the landing force—which included a handful of Free French soldiers and U.S. Rangers—could be evacuated. Many Allied prisoners were taken. The losses were heavy: 3,600 men dead or captured and 30 tanks, 33 landing craft, a Royal Navy destroyer, and 106 aircraft destroyed. The “reconnaissance in force”—devised to provide battle experience for the untried Canadian troops and to learn about German port defense methods—was classified a disaster that tarnished the reputation of its architect, the handsome, dashing Lord Louis Mountbatten, chief of Combined Operations.

Yet Operation Jubilee provided important lessons for Allied planners about the difficulty of capturing a defended port and the necessity for a preliminary bombardment and adequate equipment for beach landings. Whether the lessons were worth the price paid for them has been debated ever since.

The Idea for the ‘Mulberry Harbor”

The first and most important lesson drawn from the Dieppe assault was that the Allies could not be confident of seizing a usable port in the early stages of a future—and inevitable —invasion of the European continent. Although the British Army had long experience in expeditionary warfare, it was generally believed that a port was needed to disembark forces. The Germans, with little experience in amphibious tactics, remained convinced that any Allied invasion armada would be directed on a port so that its facilities could be brought into early use. Thus, German thinking remained focused on defending harbors and, should their capture seem likely, destroying such facilities in order to deny them to invaders. Even long after Dieppe, the Germans concluded that the Allies, when they came, would land near a port and then envelop it.

Returning from Dieppe on that fateful August 19, Royal Navy Commodore John Hughes-Hallett, a member of Mountbatten’s staff, was heard to comment, “Well, if we can’t capture a port, we will have to take one with us.”

Soon, stimulus was given to an ingenious strategic concept that would increasingly concern the Allied planners working on a second front.  It was the concept of an artificial harbor, an intriguing idea but not a new one. As early as 1917, First Sea Lord Winston Churchill had considered the possibility of a prefabricated harbor for seizing the German Frisian Islands. Guy Maunsell, an engineer, showed Hughes-Hallett plans for an artificial breakwater as early as 1940; Tipperary-born Professor John D. Bernal, known as “The Sage” at Cambridge University, devised a plan for a floating harbor; and in December 1941, staffers at Mountbatten’s Combined Operations headquarters were studying a scheme for creating sheltered water.

Three months before the debacle at Dieppe, the fertile-minded Churchill, now the British prime minister, resurrected his 1917 plan in a secret May 30, 1942, minute entitled, “Piers for Use on Beaches.” He wrote, “They must float up and down with the tide. The anchor problem must be answered…. Let me have the best solution worked out. Don’t argue the matter. The difficulties will argue for themselves.”

Thus, from the carnage of Dieppe would be developed the concept of the two “Mulberry harbors” which would play a crucial role in Operation Overlord, the great Allied invasion of Normandy on June 6, 1944.

“The Whole Project was Majestic”

General Dwight D. Eisenhower, the supreme commander who would lead the British, American, and Canadian Armies on the European continent, recalled, “The first time I heard this idea [Mulberry] tentatively advanced was by Admiral Mountbatten in the spring of 1942. At a conference attended by a number of service chiefs, he remarked, ‘If ports are not available, we may have to construct them in pieces and tow them in.’ Hoots and jeers greeted his suggestion, but two years later it was to become reality.” The code-name, Mulberry, was chosen because it would not reveal the character or purpose of the secret project.

The concept was discussed in detail by Lt. Gen. Frederick E. Morgan, Eisenhower’s able top planner, and his COSSAC (chief of staff to the supreme Allied commander) team, and it was agreed that the invasion would require the facilities of a harbor the size of Dover, Kent. COSSAC envisioned an assault on lightly held beaches “bringing a couple of artificial harbors with us.” An important factor considered by the planners was the critical Allied shortage of landing craft.

The building of the Mulberry harbors presented an enormous challenge to the British midway through the war. “The whole project involved the construction in Britain of great masses of special equipment, amounting in aggregate to over a million tons of steel and concrete,” said Prime Minister Churchill during the early stages. “This work, undertaken with the highest priority, would impinge heavily on our already hard-pressed engineering and ship-repairing industries. All this equipment would have to be transported by sea to the scene of action, and there erected with the utmost expedition in the face of enemy attack and the vagaries of the weather.” High winds and ferocious gales can whip up in a few hours in the English Channel, and the spring tides there have a play of 30 feet.

“The whole project was majestic,” said Churchill. “On the beaches themselves would be the great piers with their seaward ends afloat and sheltered. At these piers, coasters and landing craft would be able to discharge at all states of the tide. To protect them against the wanton winds and waves, breakwaters would be spread in a great arc to seaward, enclosing a large area of sheltered water. Thus sheltered, deep-draught ships could lie at anchor and discharge, and all types of landing craft could ply freely to and from the beaches. These breakwaters would be composed of sunken concrete caissons known as ‘Phoenixes’ and blockships known as ‘Gooseberries.’”

A Demonstration in a Bathtub

But there was much skepticism for the Mulberry harbors, particularly from the Americans on the Operation Overlord planning staff, and it was not until a Combined Operations conference, code-named Rattle, at Largs in central Scotland early in 1943 that acceptance first came for the ambitious concept. There, Commodore Hughes-Hallett and Royal Navy Captain Tom Hussey provided the necessary “ray of hope” as they argued the case and outlined the whole scheme. Many bright ideas were studied in wrestling with the problem of beating the English Channel and the German defenders of northern France at the same time. One of the most original suggestions was to create an artificial breakwater from a wall of bubbles released from the seabed, but this was abandoned as being far too risky.

The final plan called for a breakwater created by sunken blockships and the construction of an outer sea wall comprising huge concrete boxes—Phoenixes—some the size of three-story buildings. There would also be floating roadways, called Whales, made of articulated steel sections capable of moving with the 23-foot Normandy tide. At the end of each roadway would be a pier known as a Spud. In addition to the two Mulberry harbors, even more blockships were to be used to create five Gooseberries, which were sheltered anchorages for landing craft, one off each of the five assault beaches.

Among the planners, according to Churchill, “imagination, contrivance, and experiment had been ceaseless,” and by August 1943 a complete design had been drawn up for two full-scale temporary harbors that could be towed across the Channel from southern England to France and put into use within a few days of the initial Overlord landings. The project was demonstrated that month for the British Chiefs of Staff as they and Churchill crossed the Atlantic Ocean aboard the liner Queen Mary for the Quebec summit conference in September 1943.

Senior officers crowded into one of the vessel’s luxurious bathrooms for a simple demonstration by Professor Bernal and one of Lord Mountbatten’s scientific advisers. Standing on a toilet seat, Admiral Sir Dudley Pound, the First Sea Lord, invited his colleagues to imagine the shallow end of the bath as a beachhead. With the assistance of Navy Lt. Cmdr. D.A. Grant, Professor Bernal then floated a fleet of 20 little ships made from newspaper. Grant used a back brush to make waves, and the fleet sank.

Then, a Mae West lifebelt was inflated and placed in the bath to represent a harbor. The paper fleet was placed inside it. Once again, Commander Grant applied his brush vigorously to create waves, but they failed to sink the paper ships. The experiment convinced the officers of the importance of sheltered water and Mulberry harbors.