Vehicles landing from a 'Mulberry Harbour' at Omaha Beach.

The Dieppe Raid of 1942 had shown that the Allies could not rely on being able to penetrate the Atlantic Wall to capture a port on the north French coast. The problem was that large ships required to transport heavy and bulky cargoes needed sufficient depth of water under their keels. The Mulberries were created to provide the port facilities necessary to offload the thousands of men and vehicles, and tons of supplies necessary to sustain Operation Overlord. The harbours were made up of all the elements one would expect of any harbour: breakwater, piers and roadways.

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An early idea for temporary harbours was sketched by Winston Churchill in a 1915 memo to Lloyd George. 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. At a meeting following the Dieppe Raid, Vice-Admiral John Hughes-Hallett (the naval commander for the Dieppe Raid) declared that if a port could not be captured, then one should be taken across the Channel. Hughes-Hallett had the support of Churchill. The concept of Mulberry harbours began to take shape when Hughes-Hallett moved to be Naval Chief of Staff to the Overlord planners.

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Mulberry was the codename for all the various different structures that would create the artificial harbours. These were the "Gooseberries" which metamorphosed into fully fledged harbours. There were two harbours, Mulberry "A" and Mulberry "B". The "Mulberry" harbours consisted of a floating outer breakwater called "Bombardons", a static breakwater consisting of "Corncobs" and reinforced concrete caissons called "Phoenix", floating piers or roadways codenamed "Whales" and "Beetles" and pier heads codenamed "Spuds". These harbours were both of a similar size to Dover harbour. In the planning of Operation Neptune the term Mulberry "B" was defined as, "An artificial harbour to be built in England and towed to the British beaches at Arromanches."

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On the afternoon of 6 June 1944 (D-Day) over 400 towed component parts (weighing approximately 1.5 million tons) set sail to create the two Mulberry harbours. It included all the blockships (Corncobs) to create the outer breakwater (Gooseberries) and 146 concrete caissons (Phoenixes).

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At Arromanches, the first Phoenix was sunk at dawn on 9 June 1944. By 15 June a further 115 had been sunk to create a five-mile-long arc 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 sea-level) and the concrete caissons were festooned with anti-aircraft guns and barrage balloons.

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Mulberry 'A' was constructed at Omaha Beach and Mulberry 'B' at Gold Beach.

Aerial view of Mulberry harbour "B" at Arromanches (October 27, 1944).

On the afternoon of 6 June 1944 (D-Day) over 400 towed component parts (weighing approximately 1.5 million tons) set sail to create the two Mulberry harbours. It included all the blockships (Corncobs) to create the outer breakwater (Gooseberries) and 146 concrete caissons (Phoenixes).

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Both harbours were almost fully functional when on the 19th June a large Force 6 to 8 storm blew into Normandy and devastated the Mulberry harbour at Omaha Beach. The harbours had been designed with summer weather conditions in mind but this was the worst storm to hit the Normandy coast in 40 years.

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The destruction at Omaha was so bad that the entire harbour was deemed irreparable. 21 of the 28 Phoenix caissons were completely destroyed, the Bombardons were cast adrift, and the roadways and piers smashed.

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The Mulberry harbour at Arromanches was more protected, and although damaged by the storm it remained intact. It came to be known as Port Winston. While the harbour at Omaha was destroyed sooner than expected, Port Winston saw heavy use for eight months, despite being designed to last only three months. In the 10 months after D-Day, it was used to land over 2.5 million men, 500,000 vehicles, and 4 million tons of supplies providing much needed reinforcements in France.

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In response to this longer than planned use the Phoenix breakwater was reinforced with the addition of specially strengthened caissons. The Royal Engineers had built a complete Mulberry Harbour out of 600,000 tons of concrete between 33 jetties, and had 10 miles of floating roadways to land men and vehicles on the beach.

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Port Winston is commonly upheld as one of the best examples of military engineering.

Its remains are still visible today from the beaches at Arromanches.

Source: Wikipedia

The remains of the harbour off Arromanches in 1990.