'Mulberry' was the designation of a British pair of artificial harbours designed and assembled on the coast of Normandy in the initial stages of 'Overlord' to facilitate the rapid offloading of cargo onto the beaches taken in 'Neptune' (iii) (June 1944/March 1945).

After the Allies had landed in Normandy on 6 June, the two harbours prefabricated in the UK were moved in sections across the English Channel and assembled off 'Omaha Beach' off St Laurent sur Mer as 'Mulberry A' and off 'Gold Beach' at Arromanches as 'Mulberry 'B'.

The Mulberry harbours were intended for service until major French ports could be captured and brought back into use after repair of the inevitable demolitions by their German defenders. The 'Mulberry B' harbour at 'Gold Beach' was used for 10 months after D-Day, and more than 2.5 million men, 500,000 vehicles and 4 million tons of supplies were landed before it was fully decommissioned. Still only partially completed, the 'Mulberry A' harbour at 'Omaha Beach' was damaged on 19 June by a violent storm from the north-east. After three days the storm finally abated and damage was found to be so severe that the harbour was abandoned.

The 'Jubilee' raid on Dieppe in 1942 had revealed starkly that the Allies could not rely on being able to penetrate the 'Atlantic Wall' and take any German-held port on the north coast of France. The problem was that the major ocean-going ships of the type needed to transport heavy and bulky cargoes and stores required sufficient depth of water under their keels, together with dockside cranes, to unload their cargoes, and this combination was not available except in the already heavily defended French harbours held by the Germans. Thus the 'Mulberry' harbour concept was created to provide the port facilities required to offload the vast numbers of men and vehicles, and the huge tonnage of supplies necessary to sustain 'Overlord'. The harbours comprised all the elements typical of a major harbour: a breakwater, piers and roadways.

With the planning of 'Overlord' at an advanced stage by the summer of 1943, it was accepted that the components of the proposed artificial harbours would have to be prefabricated in the UK and then towed across the English Channel for assembly on the French coast.

The need for two separate artificial harbours, one to support Lieutenant General Omar N. Bradley’s US 1^st Army and the other to support Lieutenant General Sir Miles Dempsey’s Anglo-Canadian 2^nd Army, was agreed at the 'Quadrant' conference held in Quebec during August 1943. An Artificial Harbours Sub-Committee was established under the chairmanship of a civil engineer, Colin R. White, to advise on the location of the harbour and the form of the breakwater. The sub-committee’s first meeting was held at the Institution of Civil Engineers in London on 4 August 1943. The minutes of the meetings show that it was initially envisaged that bubble breakwaters would be used, then blockships were proposed, and finally, for lack of adequate number of blockships, a combination of blockships and purpose-built concrete caisson units.

On 2 September the Combined Chiefs-of-Staff estimated that the artificial ports would need to handle 12,000 tons per day excluding motor transport, and be capable of working in all weathers. On 4 September the approval was given on the immediate start of work. However, squabbling between the War Office and the Admiralty over responsibility was resolved only on 15 December by the intervention of the Vice Chiefs-of-Staff.

The decision was that the Admiralty was to mange the blockships, bombardons and assembly of all constituent parts on the south coast of England, and the Admiralty was also to supervise and undertake all the work needed to survey, site, tow and mark navigation. The War Office was given the task of constructing the 'Phoenix' concrete caissons, the 'Whale' roadways and protection by anti-aircraft installations. Once the harbour components had arrived off Normandy, the army was to be responsible for sinking the caissons and assembling all of the harbour’s various other elements.

For the 'Mulberry A' at 'Omaha Beach', the naval Corps of Civil Engineers would assemble the harbour from the prefabricated parts.

The proposed harbours demanded the design and construction of a large number of large caissons of various sorts from which breakwaters, piers and connecting structures to provide the roadways would be created. The caissons were built at a number of locations, mainly shipbuilding facilities and large beaches, such as Conwy Morfa, around the British coast. The work was let to commercial construction companies such as Wates Construction Balfour Beatty, Henry Boot, Bovis & Co., Cochrane & Sons, Costain, Cubitts, French, Holloway Brothers, John Laing & Son, Peter Lind & Company, Sir Robert McAlpine, Melville Dundas & Whitson, Mowlem, Nuttall, Parkinson, Halcrow Group, Pauling & Co. and Taylor Woodrow. On completion, the caissons were to be towed across the English Channel by tugs to the Normandy coast at a speed of only 4.3 kt, and then assembled, operated and maintained by the Corps of Royal Engineers under the guidance of Reginald D. Gwyther. Various elements of the 'Whale' piers were designed and constructed by a group of companies led by Braithwaite & Co., West Bromwich and Newport.

Both locations for the 'Mulberry' temporary harbours required that detailed information be created about geology, hydrography and sea conditions. To collect this data a special team of hydrographers was created in October, and this 712^th Survey Flotilla operated from the Tormentor naval base in Hamble to find and collate matters such as water depths off the German-held coast. Between November 1943 and January 1944 this team used an LCP(L), or landing craft personnel (large), to survey the Normandy coast. The special LCP(L) was manned by a Royal Navy crew and a small group of hydrographers. The first sortie was 'KJF' on the night of 26/27 November, when three LCP(L)s took measurements off the port of Arromanches, the location for 'Mulberry B'. A follow-up mission was undertaken as 'KJG' to the proposed location for 'Mulberry A', and this took place on 1/2 December: a navigational failure meant that the team sounded an area some 2,250 yards (2055 m) to the west of the intended area. Two attempts had to be made to take soundings off the Pointe de Ver. The first was 'Bellpush Able' on 25/26 December, but this had equipment problems and therefore returned on 28/29 December to complete the task.

On New Year’s Eve 1943, a Combined Operations Pilotage Party (COPP) left Gosport for the 'Gold Beach' area at Luc sur Mer. Two men of the Royal Engineers, Major Scott-Bowden and Sergeant Ogden-Smith, were landed on the beach at night in 'Postage Able' and took samples of the sand. These were crucial in determining whether armoured vehicles would be able to operate on the beach or become bogged down. The final survey was 'Bellpush Charlie' on the night of 30/31 January, but only limited information was gathered as a result of fog and because German look-outs heard the craft. Further sorties were abandoned.

An early idea for temporary harbours was sketched by Winston Churchill in a 1915 memorandum to Lloyd George: this memorandum was for artificial harbours to be created off the German islands of Borkum and Sylt. No further investigation was made and the memorandum was filed.

In 1940 the civil engineer Guy Maunsell wrote to the War Office with a proposal for an artificial harbour, but the idea was not at first adopted. Churchill issued his memorandum entitled Piers for Use on Beaches on 30 May 1942, apparently in some frustration at the lack of progress being made on finding a solution to the temporary harbour problem. Between 17 June and 6 August 1942, Hugh Iorys Hughes submitted a design concept for artificial harbours to the War Office.

At a meeting following 'Jericho' of 19 August 1942, Vice Admiral John Hughes-Hallett, the naval commander in 'Jericho', declared that if a port could not be captured then one should be taken across the English Channel for invasion purposes. Hughes-Hallett had the support of Churchill, and the concept of 'Mulberry' harbours began to take shape when Hughes-Hallett moved to be naval chief-of-staff to the 'Overlord' planners.

In the autumn of 1942, the chief of combined operations, Vice Admiral the Lord Louis Mountbatten, outlined the requirement for piers at least 1 mile (1.6 km) long at which a continuous stream of supplies could be handled, including a pier head capable of handling 2,000-ton ships.

In July 1943 a committee of eminent civil engineers (Colin R White as chairman, J. D. C. Couper, J. A. Cochrane, R. D. Gwyther and Lieutenant Colonel Ivor Bell) was created to advise on the manner in which a number of selected sites on the French coast could be converted into sheltered harbours. The committee initially investigated the use of compressed air breakwaters before eventually deciding on blockships and caissons.

In August and September 1943 a trial of three competing designs for the cargo-handling jetties was set up together with a test of a compressed-air breakwater. The pier designs were by the civil engineer Hugh Iorys Hughes who developed his 'Hippo' piers and 'Crocodile' bridge spans; Ronald Hamilton, working at the Department of Miscellaneous Weapons Development, who devised the 'Swiss Roll' which consisted of a floating roadway made of waterproofed canvas stiffened with slats and tensioned by cables; and Lieutenant Colonel William T. Everall and Major Allan Beckett of the War Office’s 'Transportation 5 Department, who designed a floating bridge linked to a pier head (the latter had integral 'spud' legs that were raised and lowered with the tide).

The western side of Wigtown Bay, in the Solway Firth, was selected for the trials as the tides were similar to those on the expected invasion beaches in Normandy. A harbour was available at Garlieston, and the area’s remote nature would simplify security matters. A headquarters camp was erected at Cairn Head, about 5 miles (8 km) south of Garlieston. Prototypes of each of the designs were built and transported to the area for testing by Royal Engineers based at Cairn Head and in Garlieston. The tests revealed various problems: the 'Swiss Roll', for instance, would take a maximum load of only a 7-ton truck in the Atlantic swell. However, the final choice of design was determined by a storm during which the 'Hippos' were undermined causing the 'Crocodile' bridge spans to fail and the 'Swiss Roll' was washed away. Tn5’s design proved the most successful, and Beckett’s floating roadway (later codenamed 'Whale') survived undamaged. The design was adopted and 10 miles (16 km) of 'Whale' roadway were manufactured under the management of J. D. Bernal and Brigadier Bruce White, the Director of Ports and Inland Water Transport at the War Office.

'Mulberry' was the codename for all of the various different structures that would be used for the creation of the artificial harbours. These were the 'Gooseberries' which metamorphosed into a pair of fully-fledged harbours. Each 'Mulberry' harbour comprised a 'Bombardon' floating outer breakwater, a 'Corncob' static breakwater, 'Phoenix' reinforced concrete caissons, 'Whale' and 'Beetle' floating piers or roadways. and 'Spud' pier heads. Each of the planned harbours was of a size similar to that of Dover harbour. In the planning of 'Neptune' (iii), the term 'Mulberry B' was defined as an 'artificial harbour to be built in England and towed to the British beaches at Arromanches'.

The 'Mulberry' harbour assembled on 'Omaha Beach' at St Laurent sur Mer was for the support of the US invasion forces. 'Mulberry A' was not securely anchored to the sea bed as was the case with 'Mulberry B' used by the British, resulting in such severe damage during the English Channel storm of 19 June that it was deemed irreparable and continued assembly was therefore terminated, although the existing section was quickly repaired and by 23 June the tonnage landed there was greater tan that of 18 June, and this tonnage continued to increase to the end of the month.

'Mulberry B' was the harbour assembled on 'Gold Beach' at Arromanches for use by the British and Canadian invasion forces. The harbour was decommissioned six months later as the Allied forces were able to use the recently captured and reopened port of Antwerp in Belgium to offload troops and supplies closer to the current front line.

'Corncobs' were ships which crossed the English Channel, either under their own steam or towed, and were then scuttled to act as breakwaters and create sheltered water at the five landing beaches. Once in position, the 'Corncobs' created the sheltered waters known as 'Gooseberries'. 'Gooseberry 1' for 'Utah Beach' comprised 11 ships, 'Gooseberry 2' for 'Omaha Beach' 14 ships, 'Gooseberry 3' for 'Gold Beach' 16 ships, 'Gooseberry' 4 for 'Juno Beach' 11 ships, and 'Gooseberry 5' for 'Sword Beach' nine ships.

'Phoenixes' were reinforced concrete caissons constructed by civil engineering contractors around the coast of the UK, collected and sunk off Dungeness in Kent and Pagham in West Sussex before 'Neptune' (iii). There were six different sizes of caisson with individual displacements of about 2,000 to 6,000 tons, and each unit was towed to Normandy by two tugs at a speed of about 3 kt. The caissons were initially sunk for await the start of 'Neptune' (iii) and then refloated by engineers for movement and use. A US naval officer, Captain Edward Ellsberg, already known for the rapid refloating of ships scuttled at Massawa in Eritrea and at Oran in Algeria, was brought in to accomplish the task, although not without obtaining Churchill’s intervention in shifting the task from the Royal Engineers to the Royal Navy. Once refloated, the 'Phoenixes' were towed across the English Channel to form the 'Mulberry' harbour breakwaters together with the 'Gooseberry' blockships. Ellsberg travelled to Normandy on one of the caissons, and once there helped to clear the beaches of wrecked landing craft and vehicles.

'Bombardons' were large cross-shaped floating breakwaters, each measuring 200 ft (61 m) by 25 ft (7.6 m) and fabricated from steel. These were anchored outside the main 'Gooseberry' and 'Phoenix' breakwaters. A total of 24 'Bombardons', attached to one another with hemp ropes, create a breakwater 1 mile (1.6 km) long. During the storms at the end of June 1944 some 'Bombardons' broke up and sank, while others suffered the parting of their anchor cables and drifted down onto the harbours, possibly causing more damage to the harbours than the storm itself. The design of the 'Bombardons' was the responsibility of the Royal Navy while the Royal Engineers were responsible for the design of the rest of the 'Mulberry' harbour equipment.

'Whales' were the dock piers, which were the floating roadways that connected the 'Spud' pier heads to the shore. Designed by Allan Beckett, the roadways were made from innovative torsionally flexible bridging units that had a span of 80 ft (24.4 m), mounted on 'Beetle' pontoon units of either steel or concrete. After the war many of the 'Whale' bridge spans from Arromanches were used to repair bombed bridges in France, Belgium and the Netherlands.

The 'Beetles' were pontoons which supported the 'Whale' piers. They were moored in position using wires attached to 'Kite' anchors, which were also designed by Beckett. These anchors had a holding power so great that very few could be recovered at the end of the war. The Royal Navy was dismissive of Beckett’s claims for his anchor’s holding ability. so 'Kite' anchors were not used for mooring the 'Bombardons'.

The 'Spuds' were the pier heads or landing wharves at which ships were unloaded. Each of the 'Spuds' comprised a pontoon with four legs that rested on the sea bed to anchor the pontoon, yet allowed it to float up and down freely with the tide.

On the afternoon of 6 June 1944, more than 400 towed component parts, with a combined weight of about 1.5 million tons, departed the British coast as elements for the two 'Mulberry' harbours. These components included all the 'Corncob' blockships to create the 'Gooseberry' outer breakwaters and 146 'Phoenix' concrete caissons.

At Arromanches, the first 'Phoenix' was sunk at dawn on 8 June, and by 15 June a further 115 had been sunk to create an arc, 5 miles (8 km) long, between Tracy sur Mer in the west to Asnelles in the east. To protect the new anchorage, the superstructures of the blockships, which remained above the water, and the concrete caissons were festooned with anti-aircraft guns and barrage balloons.

At 'Omaha Beach', and arriving first on 6 June, were the 'Bombardons' followed one day later by the first of the blockships. The first 'Phoenix' was sunk on 9 June and the 'Gooseberry' had been completed by 11 June. By 18 June two piers and four pier heads were working. Though this harbour was abandoned late in June, the beach continued to be used for landing vehicles and stores using LSTs (landing ships, tank)/ Using this method, the US forces were able to unload a higher tonnage of supplies than at Arromanches. Salvageable parts of the artificial port were later sent to Arromanches to repair the Mulberry there.

Both harbours were almost fully functional when on 19 June a large north-east storm, of Force 6 to 8 strength, hit the Normandy coast and devastated the 'Mulberry A' harbour at 'Omaha Beach'. The harbours had been designed for service in summer weather conditions, but this was the worst storm to hit the Normandy coast in 40 years. The destruction at 'Omaha Beach' was so bad that the entire harbour was deemed irreparable: 21 of the 28 'Phoenix' caissons had been wholly destroyed, the 'Bombardons' were adrift, and the roadways and piers had been smashed. The 'Mulberry A' harbour at Arromanches was more protected, and although damaged by the storm it remained intact. While the harbour at 'Omaha Beach' was destroyed sooner than expected, that at Arromanches saw heavy use for eight months, despite being designed to last for only three months. In the 10 months after 6 June, it was used to land more than 2.5 million men, 500,000 vehicles and 4 million tons of supplies. In response to this longer-than-planned use, the 'Phoenix' breakwater was reinforced with the addition of specially strengthened caissons. The Royal Engineers had assembled a complete 'Mulberry' harbour out of 600,000 tons of concrete between 33 jetties, and had 10 miles (16 km) of floating roadways to land men and vehicles on the beach. 'Mulberry B' is commonly cited as a classic example of military engineering, and its remnants are still visible.

Some troops of the 23^rd Headquarters Special Troops (colloquially known as the 'ghost army'), a 1,100-man deception force, arrived in Normandy two weeks after 'Neptune' (iii) to simulate a 'Mulberry' harbour. The deception was created in such a way that at night its lights drew German artillery fire away from the real 'Mulberry' harbours.

After the end of the war, some historians (largely American) claimed that although the 'Mulberry' effort was a success, the vast resources committed to it may have been wasted as the US forces were supplied mostly over the beaches without the use of a 'Mulberry' right through to September 1944. By the end of 6 June, 20,000 troops and 1,700 vehicles had landed on 'Utah Beach', which was the narrowest of the five Allied landing areas. At 'Omaha Beach' and 'Utah Beach', some 6,614 tons of cargo were discharged in the first three days: one month later the two beaches were handling 9,200 tons and, after a further month, 16,000 tons per day. This increased until 56,200 tons of supplies, 20,000 vehicles, and 180,000 troops were discharged each day at those beaches. Initially, the 'Mulberry harbours provided less than half the total landed on good-weather days.

By the end of June, more than 289,827 tons of supplies had been offloaded onto the Normandy beaches. Up to September, the US forces were supported largely across the beaches, primarily without the use of 'Mulberry A'.

'Mulberry B' was substantially reinforced with elements salvaged from 'Mulberry A', and the 'Phoenixes' were pumped full of sand to give them greater stability, and such measures undoubtedly explain the extended service life of the British port. Furthermore, the planners obviously underrated the capacities of open beaches. The very considerable tonnage capacities subsequently developed at both the 'Utah Beach' and 'Omaha Beach' were thus of huge significance in the prosecution of 'Overlord' and subsequent operations.