The 'Mulberry Harbours' was a WW2 civil engineering project of immense size and complexity. The floating harbours were designed to provide port facilities during the invasion of Normandy in June 1944 until French ports like Cherbourg were captured. How did they erect two harbours, each the size of Dover, in just a few days in wartime when Dover took 7 years?
When it came to ousting the Germans from their entrenched defensive positions along the 'Atlantic Wall,' planners knew that blockading and attack by air would not be sufficient. The Germans would defend their front lines with great vigour and only a large scale landing of men, their equipment and supplies would be up to the task. In the crucial days and weeks following the landing, the Allies could ill afford delays in supplying their advancing forces. Intelligence reports indicated that French seaports would be heavily defended by German forces and they were liable to be disabled in the event of imminent Allied occupation. Planners also drew on the main lesson learnt from the ill-fated Dieppe Raid that heavily defended ports could not be taken without crippling losses. The plans therefore envisaged a need to create secure harbour facilities away from heavily defended ports and close to the landing beaches.
Harbour facilities were needed quickly where none existed. That was clear enough but conventional construction techniques required detailed ground and seabed survey information, precise building plans and the assembly of a highly skilled construction force of thousands; an impossible task under normal circumstances but particularly so when the time available for the construction phase was measured in days and the construction sites were within easy range of enemy aircraft and long range guns!
After Normandy was chosen as the location for the 2nd front the decision to design and construct two artificial harbours in the relative safety of the UK mainland was agreed, but, it must be said, with misgivings especially on the part of some high ranking Americans. To address the issue of skill shortages the design was to allow for the transportation and assembly of the many harbour components by a competent workforce under the supervision of engineers.
In 1917 Churchill drafted detailed plans for the capture of two islands, Borkum and Sylt, which lay off the Dutch and Danish coasts. He envisaged using a number of flat bottomed barges, or caissons, measuring 37m x 23m x 12m which would form the basis of an artificial harbour when lowered to the seabed and filled with sand. Events moved on and Churchill's proposal was filed away and was never published.
In 1941, Hugh Iorys Hughes, a quiet unassuming Welshman from North Wales had similar ideas. He was a successful civil engineer living in London when he submitted plans to the War Office. Their potential value was not recognised until Hughes' brother, a Commander in the Royal Navy, drew the plan to the attention of more senior officers. This intervention brought Hughes and his ideas to the fore. It was to be the beginning of a long association with the Mulberry project.
Other accounts credit Professor J D Bernal with similar ideas expanded upon by Brigadier Bruce White who later helped draw up plans for the final design. He was greatly assisted by Allan Beckett whose "whale" design for the roadway was selected in preference to Hamilton's Swiss Roll and Hughes' concrete Hippo (more information below). With a project of this size and complexity it is not possible to say that the idea was the property of any individual but all of the above were major players in the story of Mulberry Harbours. Both Bruce White and Allan Beckett wrote papers about aspects of Mulberry, details of which can be found at the bottom of this page under Reading Material & Websites.
Early in 1941 a new department within the War Office was set up code named 'Transportation 5' (Tn5) under Major General D J McMullen. It had responsibility for port engineering, repairs and maintenance. The Mulberry project and the need to construct sufficient embarkation points on the shores of the UK, soon became its top priorities. Under the command of civil engineer Bruce White their first project was to construct two military ports in the Clyde estuary one of which was the Gare Loch.
There were many meetings with the Americans about the options to provide sheltered harbours.... sunken ships, concrete caissons, concrete pontoons, collapsible canvas floating barriers and Pykrete to name but some. There was scepticism on both sides of the Atlantic and some believed that Mulberry was even more fanciful an idea than Pykrete! To overcome the doubters in his own ranks Mountbatten called them to a meeting in one of the bathrooms of the Queen Mary. They were en route to an important meeting with the Americans in Quebec where the matter of artificial harbours would be decided. As they entered the bathroom they saw a partially filled bath, 40 or so ships made out of newspaper and a Mae West lifebelt.
Half the 'fleet' was placed in the bath and the most Junior officer present in the crowded bathroom, Lt Commander Grant, RN, was asked to make waves with the back of a brush. In no time the vessels sank. The demonstration was repeated this time with the 'fleet' floating inside the Mae West. To the immortal command "More waves please Lieutenant Grant" the heavily braided onlookers saw that all the vessels survived.
One USA sceptic, Admiral John Leslie Hall Jr., US Navy Commander, was scathing of the idea, predicting that the Mulberries would never stand up to the rigours of the English Channel and, in any event, he could unload 1000 LSTs at a time on open beaches... more than enough to supply the advancing Allied forces. His prediction was, at least in part, later proved to be correct in the case of Mulberry A (details below), but the balance of opinion was in favour of the project and approval was given to proceed. The task was given to Mountbatten's Combined Operations. However, he soon realised that the resources needed were way beyond those of his Command and he contracted out the operational aspects to the War Department.
Three designs were selected for further evaluation. The first from the War Office was for flexible steel bridges on pontoons of steel or concrete with pier-head units on adjustable legs to take account of the tides. The second from the Admiralty was a flexible floating construction of timber and canvas held together with steel cables and similar in appearance to a Swiss Roll in its stored condition. The third from Iorys Hughes envisaged the use of steel bridges to be mounted on concrete caissons and floated to the sites and sunk in position. Initially none were to be protected by breakwaters.
The search was on for 'test' beaches with characteristics similar to those of Normandy - flat, sandy, remote and sparsely populated to ensure an effective security cordon. After exhaustive surveys, Wigtown Bay on the Scottish side of the Solway Firth, with its nearby harbour of Garlieston, was chosen. The whole area from Garlieston to the Isle of Whithorn (not an island!) was declared off limits to all except local fishermen. Work started on the construction of a military camp at Cairnhead to accommodate the increasing numbers of engineering personnel (Sappers) with an additional 200 men being accommodated in the village hall in Garlieston.
The Morfa area was transformed into a huge construction site Hughes' three 'Hippo' caissons were towed to the site in Rigg Bay near Garlieston. Two 'Croc' roadways were attached to the metal bars on the Hippos and various combinations were tested in a variety of weather and tidal conditions. Fully laden vehicles were driven across the roadway. The testing proved invaluable since the behaviour of the components could be analysed and corrective action taken where necessary. It was found that the floating piers did not rise and fall with the tide as predicted but Hughes found a solution in the provision of adjustable spans between the Hippos and the roadway. A more serious problem was the unexpected pitching and yawing of the Hippos causing the attached Croc roadways to buckle. Hughes proposed the construction of Hippos of diminishing size on which the roadways would sit.
Hughes' design was not alone in experiencing problems. When Hamilton's Swiss Roll roadway was tested with a 3 ton tipper truck the roadway sank in under two hours. Adjustments were made but further tests in the open sea confirmed that the heaviest load that could be carried was 7 tons - far below what was necessary for the movement of tanks. The Swiss Roll roadway design was soon abandoned. In the end it was Beckett's flexible bridging units, supported on pontoons, that produced the best results.
However, Churchill was not happy with the rate of progress. He had sent a memo to Mountbatten on the 30th May 1942... "Piers for use on beaches. They must float up and down with the tide. The anchor problem must be mastered. Let me have the best solution worked out. Don't argue the matter. The difficulties will argue for themselves." Progress at first was slow as discussions on competing ideas by the many interested parties were considered. Churchill penned a number of increasingly irate messages in the following months culminating in this one of 10 Mar 1943. "This matter is being much neglected. Dilatory experiments with varying types and patterns have resulted in us having nothing. It is now nearly six months since I urged the construction of several miles of pier." In response some organisational changes were made to "get a grip" on the project.
There had been tensions between the War Office and the Admiralty which sometimes resulted in poor co-operation and bad communications. After earlier allocations of responsibility had failed to resolve matters the War Office was tasked to design the caissons and oversee the development of the pier-heads and piers while the Admiralty were tasked to design and oversee the development of the floating breakwaters. This agreement was later refined to take account of continued Admiralty concerns about the berthing and navigation guides and it was therefore agreed that they would be responsible for the towing all the components across the channel, the layout and positioning of the harbours and the navigational channels and moorings.
The early designs did not envisage protective breakwaters but it became clear that an area of calm water would be required.. In addition to the breakwaters, included in the final plans, other water calming measures considered included "bubble breaker" and "lilo".... the former involved pumping high pressure air along perforated pipelines causing a large volume of compressible air in the sea sufficient to absorb the power of heavy breakers. The latter were large canvas bags extending some 4m below the waves and 3m above. They were inflated to low pressure and operated on a similar basis to the bubble breaker in that they would absorb the power of the waves by allowing the air they contained to be compressed.
On conclusion of the tests a final design was decided upon. There would be two harbours each comprising two breakwaters, offshore and flanking, made from hollow ferro-concrete caissons. To provide extra protection 70 obsolete merchant and navy vessels (block-ships) would be sunk to fill gaps in the protection provided by the caissons. Inside the resultant protective cordons there would be pier-heads connected to the shore by Beckett's floating steel roadways. In view of Iorys Hughes' commitment to the project and expertise he was invited by Churchill to serve the project as a consultant.
Mountbatten's ideal specification was for a pier a mile long that could withstand gale force winds and be capable of berthing large coasters. To do this the artificial harbours would need to provide sheltered conditions and be larger than the port of Dover which had taken 7 years to build in peacetime! Within the sheltered areas stable floating quays would be located some distance from the beaches to provide sufficient water depth (6.7 meters) for the docking vessels. These quays would be linked to the beaches by floating roadways to allow the discharged goods and equipment to be transported ashore in fleets of lorries. Two harbours would be required - Mulberry A for the USA beaches of Omaha and Utah and Mulberry B for the British and Canadian beaches of Gold, Juno and Sword. The designs would allow for the floating caissons to be secured in place in four days. Each harbour would have a capacity of 7000 tons of vehicles and supplies per day.
For security reasons randomly selected codes were used to describe the various components of the two Mulberry Harbours viz..
~ Breakwaters ~
~ Pierheads ~
~ Roadways ~
The final configuration of all these units when assembled and positioned can be seen in this photograph although the Bombardons were too far out to be seen here.
The success of the operation would depend on accurate and detailed topographical information about the beaches and coastal towns along the French coast. Aerial photographs helped identify likely locations but, to obtain more detailed views, the Government appealed to the public for holiday photographs and postcards of unspecified coastal areas of France. However much more detailed information on the target beaches and their approaches was required. Local conditions such as the composition of the beaches, hidden underwater banks, German defensive obstacles, depth of water, tidal conditions etc would all be taken into account in the planning of the project. The stakes were very high - bad intelligence could jeopardise the whole vast project.... there was no room for error.
On New Year's eve 1943, under the leadership of 24 year old Major Logan Scott Bowden of the Royal Engineers, a unit set out in motor torpedo boats to reconnoitre the area around Luc-sur-Mer. They transferred to a hydrographical survey craft and moved closer to shore before Major Logan and Sgt Bruce Ogden-Smith swam to the beaches where they took samples of sand, mud, peat and gravel which they stored in labelled tubes. They were careful not to leave behind any evidence of their visit lest the Germans became alerted to their clandestine activities - much of their lateral movement along the beaches was below the tide mark! Their mission was a total success.
A month or so later, this time using a midget submarine for transport (towed part of the way), the area to the west of Port-en-Bessin and Vierville was visited and a few weeks later the Omaha beach area. Two scale models of the landing beaches were prepared using all the information gathered. One was held by the War Department in room 474 of the Great Metropole Hotel in London and a duplicate in the Prime Minister's room in the War Cabinet Offices - two of the most secret rooms in the country.
At Cairnryan, just north of Stranraer in south west Scotland, the information gathered about the beaches was used to construct a "life size" reproduction of the beaches. This would allow the planners to assess the effectiveness of the current landing techniques and the movement of men and machinery over the terrain.
The scale of the project was enormous and was in danger of over-stretching the capacity of the UK's civil engineering industry. From late summer of 1943 onwards three hundred firms were recruited from around the country employing 40,000 to 45,000 personnel at the peak. Men from trades and backgrounds not associated with the construction industry were drafted in and given crash courses appropriate to their work. Their task was to construct 212 caissons ranging from 1672 tons to 6044 tons, 23 pier-heads and 10 miles of floating roadway.
Most of the concrete caissons were manufactured on the River Thames and the River Clyde in some cases using hastily constructed dry docks. The steel "Beetle" floats were assembled in Richborough, Kent, the concrete Beetles at Southsea, Marchward and Southampton and the pier-heads and buffer ramps at the Morfa site Hughes had used for the manufacture of his Hippo caissons. Trials continued to be run in the Garlieston area of the Solway, even during the manufacturing phase, on for example, the buffers.
Hughes' involvement continued throughout the manufacturing period and beyond. He helped identify Selsey and Dungeness on the south coast of England as ideal places to "park" the completed caissons until needed. Also closely involved in the planning for D-Day and the Mulberry Harbours was Sir Harold Werner. He was a rather overbearing, single minded individual who did not court popularity and consequently his valuable service in finding solutions to insurmountable problems and generally keeping the project on schedule, went largely unrecognised after the war.
A large number of British and USA tugs were requisitioned to tow the Mulberries from their assembly point near Lee-on-Solent to France. Operation Corncob got underway when the first of the tugs set off on June 4 later to hold their position in mid channel when D-Day was delayed by a day. When the invasion finally got underway most caissons were positioned about 5 miles off the French coast. Click here for information about the British and American tugs involved.
Responsibility for Mulberry B off Aromanches fell to the No 1 Port Construction and Repair Group. They received orders to sail on June 6 1944 (pm) and by the early hours of June 7, under the command of Lt Col Mais, markers were in place at high tide level and on higher ground, for alignment purposes, for the first two piers. Elsewhere further out to sea marker buoys for the caissons and block ships were positioned under the command of Lt Col Landsdowne of the RN. This done the block-ships slipped their moorings in Poole harbour and sailed for France on their final voyages. Scuttling them in pre-determined 'overlapping' positions was a tricky operation but essential to ensure effective protection against high seas and fast flowing tides.
Similar operations were in progress at Mulberry A off Vierville-Saint-Laurent but here the vessels came under heavy enemy fire. The tugs, which had accompanied the vessels, and which were to assist in their final positioning, dispersed earlier than planned. By a stroke of good fortune the 2nd and 3rd block-ships were sunk by the Germans in roughly the correct positions. In all 5 Gooseberries were positioned to provide the best protection for the two Mulberry harbours and for other beach landing points at Utah, Courseulles, 11k east of Arromanche, and Ouistreham. These breakwaters provided a good measure of protection during and after the construction of the 2 Mulberry harbours and in the other beach locations. The UTAH beach was a major logistical supply base for the Americans up to November '44 thanks to the protection afforded by its 'Goosberry.'
The Bombardons were towed out on June 6 to their moorings which had been laid previously by boom laying craft. However a mistaken order resulted in the Bombardons being placed in water some 20m to 24m deep rather than the designed 13m and they were strung out in a single line when there should have been a double line. The effectiveness of this outer barrier had been compromised.
On D+1 the caissons, each with a 4 man crew, two sailors and an anti-aircraft gun emplacement, were towed to positions about a mile off-shore and handed over to a fleet of powerful harbour tugs which manoeuvred them into their final positions. The caissons' sea valves were opened until they settled at previously agreed depths. Each Mulberry was about a mile long and stood about 30 ft (9m) above sea level at low tide and 10 ft (3m) at high tide. The block-ships at Mulberry B were all in position by June 13th and formed two crescent shaped harbours which accommodated 75 Liberty ships and small craft.
The installation of the stores and LST piers proved to be more of a problem. The tows began to arrive at Mulberry B on D+4 and work continued throughout the night. Choppy seas made the manoeuvring of the bridging spans very difficult. By D+8 the stores pier and roadway amounting to 1.2k was in place and operational. The 2nd stores pier was operational by July 8. It was later discovered that the Beetle floats to support the roadway had been positioned in an alternate pattern rather than opposite each other as the design intended. This proved to be a costly error when consequential stability problems were experienced. The Luftwaffe attacked Mulberry B on July 15 but such were the defences that 9 of the 12 Messcherschmitts were shot down.
The photo opposite (and close-up) were sent in by Scott Blyth who wrote; On June 12, 1944 my father, Lt. John S. Blyth, flew a photo recce mission to the Loire Bridges. It was sortie 1841 of the 14th Squadron of the 7th Photo Group (USAAF). The targets were La Huichetiere, Nantes Airfield, Le Port Boulet Bridge damage assessment and the Loire Bridges from Nantes to Tours. He was based at Mt Farm near Oxford and on that mission flew Spit MK XI PA 841. Crossing the coast over Omaha Beach he took at least one photo of the beachhead. It appears to contain one of the piers of Mulberry A.
Mulberry A was in use for less than 10 days when, on June 19, it was severely damaged by the worst period of sustained severe weather for 40 years. Out of 31 caissons laid in position 21 were damaged beyond repair with broken backs and sides. Mulberry A was never used again and parts of it were scavenged to repair damage to Mulberry B. The Americans quickly reverted to the traditional methods of unloading from landing craft and DUKWs directly onto the beaches often coming in on one tide and leaving on the next. Such was their success that on occasions they exceeded the impressive performance achieved at Mulberry B.
Each day around 9000 tons were landed via Mulberry B until the end of August by which time Cherbourg port became available for use at least in part and, towards the end of the year, after the capture of Walcheren, the port of Antwerp. Mulberry B was in use for 5 months during which time over 2 million men, half a million vehicles and 4 million tons of supplies passed through the harbour. During this period several additional caissons where used to reinforce weak points in the breakwater. [Photos below; HMLST 427 discharging her cargo onto Mulberry A prior to the storm.]
The Mulberry project was for certain a great feat of engineering - a highly complex task completed in just 6 months of manufacture, by hundreds of contractors in dozens of locations, under wartime conditions and a serious shortage of skilled labour. The planners were heavily influenced by the paramount need to secure the Allied supply line since the invasion would otherwise stall and collapse as the enemy regrouped and drew on their reserves. There are those who believe that Mulberry was unnecessary as exampled by the Americans success in landing supplies directly onto the beaches after the abandonment of Mulberry A. We'll never know, with any degree of certainty, what would have happened had Mulberry never been built... and that for many is all the justification needed for the planners' decision to authorise the project.
With the exception of those who were there in the summer of 1944, there is nothing in our collective experience that allows us to imagine the vastness of the operation and the absolute necessity to move men, supplies, munitions and equipment to the right place at the right time. Even the logistics faced by the largest supermarket chains today pale into insignificance when compared to the task faced by the planners in the early 1940s. They faced an awesome responsibility and the wider world faced dire consequences in the event of failure to deliver.
The Supermarket scenario offers an opportunity to put the scale of the task into a modern context. It has been calculated that each serviceman needed 6.5lb (3Kg) per day to sustain him in the field. On this basis1000 men needed around 2.5 tons, 100,000 needed 250 tons and 1,000,000 2,500 tons per day!. As the size of the invading force grew so did the daily demand for supplies. Then there were the lorries, tanks, artillery pieces, ammunition, military field hospitals, mobile radar and communications units etc etc. all of which had to be transported across the channel. Over 4,000 vessels plied the waters between the UK and Normandy from D-Day and the contribution of Mulberry B in speeding up the operation and securing the supply chain in adverse weather conditions, is beyond question. The majority of vessels in use were not capable of beach landings.
After the war at the Nurembeurg trials, Albert Speer gave the enemy perspective on the Mulberry Harbours and their Atlantic Wall defences. 'To construct our defences we had in two years used some 13 million cubic meters of concrete and 1.5 million tons of steel. A fortnight after the landings by the enemy, this costly effort was brought to nothing because of an idea of simple genius. As we know now, the invasion forces brought their own harbours, and built, at Arromanches and Omaha, on unprotected coast, the necessary landing ramps."
[Photos. Top looking east towards Arromanche courtesy of Nigel Stewart and bottom a stranded caisson in Portland Harbour still dominating the skyline after 70 years (2013).]
There are around 300 books listed on our 'Combined Operations Books' page which can be purchased on-line from the Advanced Book Exchange (ABE) whose search banner checks the shelves of thousands of book shops world-wide. Type in or copy and paste the title of your choice or use the 'keyword' box for book suggestions. There's no obligation to buy, no registration and no passwords. Click 'Books' for more information.
Memoirs of a Concrete Consultant by Victor S Wigmore. The author was a consulting engineer on the Mulberry Harbour project in the SE of England. His speciality was in the use of concrete. Chapter VII of his book describes aspects of his work on Mulberry. Pub in 1979 by New Horizon, 5, Victoria Drive, Bognor Regis, West Sussex. ISBN 0 86116 127 0.
A Harbour Goes to War - The Story of Mulberry and The Men Who Made it Happen by Jane Evans, E. Palmer & R. Walter. The Mulberry harbours were a vital link in the supply chain following the Normandy invasion. This is the story of their development in Scotland, and their use, using personal anecdotes and photographs. ISBN 1873547307.
Force Mulberry by Alfred Stanford. The Planning & Installation of the artificial harbor off U.S. Normandy Beaches. William Morrow and Co, 1951.
Conwy Mulberry Harbour by Mark Hughes. Paperback, ISBN 0-86381-757-2.
Code Name Mulberry by G Hartcup. The Planning, Building and Operation of the Normandy Harbors Published 1977 David & Charles, London & Hippocrene Books Inc NY.
A harbour called Mulberry by Sir Bruce White gives an organisational account of the Mulberry project. Available as PDF download.
Some (engineering) Aspects of the Design of Flexible Bridging, Including 'Whale' Floating Roadways by the engineer/designer Allan Beckett. Available as PDF download.
Untold Stories of D-Day - National Geographical June 2002.
Detailed account of Mulberry B including tables of the movement of men and materials through the completed harbour.
See Garlieston today where the three Mulberry prototypes were tested in 1943/44.
Click here for archive
information about the British and American Tugs used to transport/tow the Mulberry Harbours
across the English Channel.
Garlieston Today. I'm a retired Territorial Army Major and have an interest in military history. My uncle was involved in the building of the Mulberry Harbours during the Second World War and since I live just a few miles from the location of the top secret trials mentioned above, I have a special interest in the subject. With the eye of a retired Chartered Surveyor, I inspected the remains of the Mulberry Harbours in France and also the location of the various works at Garlieston. A study of the information contained within the display and exhibition at Garlieston and on the Combined Operations website added to my field research. Until recent times very few local people talked about the Mulberry trials which must have had a big impact on such a small community. They were certainly capable of keeping a secret!
The village today comprises a small port on the east coast of The Machars in the former county of Wigtownshire. Its origins date back to the 1780s when Lord Garlies planned and built a small port on the sheltered shores of what later became known as Garlieston Bay. By 1800 Garlieston had a population of 500 and provided port facilities for 10 trading vessels. A pier was built to expand the harbour’s capacity in 1816. Local industry also expanded to include the manufacture of sailcloth and ropes and the construction of ships. At the start of the 1900s special excursions to the Isle of Man were popular with easy access by rail down to the harbour quayside to waiting steamers. However, during the great depression of the 1930s the excursions ceased and the railway closed in 1950.
In common with many ports in rural Scotland Garlieston's role as a commercial port has been replaced by leisure activities including yachting, other leisure craft and a conveniently located Caravan Club site. In addition there is an excellent exhibition entitled “GARLIESTON’S SECRET WAR”. The exhibition includes photographs and commentary highlighting Garlieston’s role in the Mulberry Harbour development. There is also an excellent model of a Mulberry harbour and a video presentation featuring the Mulberry Harbours and D-Day together with books and souvenirs.
Mulberry at Dungeness. We visited Gairleston in Scotland last year and were interested to find that experimenting had been done there for the Mulberry Harbour. I live near Dungeness at Littlestone. You will be aware that bits of the Harbour broke away and one piece landed off our beach. It's still clearly visible to this day. It is now a memorial where wreaths are placed from time to time. I enclose a photograph. Several houses by the beach have Mulberry in their names. Norma Oakeley.
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