Mulberry harbour

The Mulberry harbor is an artificial port built on the coast of Normandy during World War II to allow the supply of the Allied armies in the days after the Normandy landings. In fact, two ports were assembled off the beaches of Calvados, but only one Arromanches is operational, the second Omaha Beach before being destroyed by a storm June 19, 1944. The construction of this port to the Allies avoided having to take a deep water port directly. The Mulberry harbor consisted of various large prefabricated in England and shipped assembled on the Normandy coast. This artificial harbor has often been put forward as having ensured the success of the Battle of Normandy and presented as an example of military engineering and logistics. But historians now relativize some role until the restart of the port of Cherbourg, a majority of the Allied supply will be made ​​by a direct landing on the beach or by the use of small ports on the Normandy coast.


The failure of the Dieppe Raid of 1942 showed that the Allies would be very difficult to take a major port of the French Channel coast, most of the elements fortified Atlantic Wall created by the Germans along the coast. The control of a port was needed from the days following the landing to transport vehicles, supplies and men to support the Operation Overlord. An artificial harbor consists of transportable elements, and that could get off the landing beaches would be the answer to this problem. The code name of the project, “Mulberry” (in English: blackberry), gave birth to the expression of Mulberry harbor.

The name of the man behind the idea of the Mulberry harbor is disputed, but there are some Iorys Hugh Hughes, a Welsh engineer who submitted the original plans from the idea to the War Office UK, Professor John Bernal and Vice-Admiral John Hughes-Hallett. At a meeting following the failure of the Dieppe raid, it said that if a port could not be taken, then it would bring one. The idea at the time, was taken as a joke, but Churchill became interested and the concept of Mulberries ports began to take shape when Hughes-Hallett was appointed Chief of Naval Staff of Operation Overlord. At the Quadrant conference in Quebec in August 1943, the project is presented by the War Office. Various Allied leaders validate the project.

In 1943, a trial of three different designs of artificial harbor was launched and tested in the real Solway Firth in Scotland. Iorys Hugh Hughes developed his thrown “Hippo” and bridges “Crocodile”, employing 1000 people just to build version test, the “Swiss Roll” (Swiss balance) of Hamilton which was a floating channel and a system of flexible bridges supported by floating pontoons designed by Allan H. Beckett. The tests gave mixed results (the Swiss balance could only carry trucks up to 7 tons in normal swell). However, the final choice was made ​​during a storm in which the “Swiss Roll” was carried and “Hippos” were undermined by the sea water floating pathways Beckett (who had the code name Whale) did not suffer damage. They were therefore retained.


The proposed ports consisted of three parts:

jetties and artificial dams, to create a body of water sheltered

the docks,

the ‘floating channels, connecting the docks to the coast.

The theoretical quantities announced the following figures:

500 ha, equivalent to the port of Dover

6 km of piers and breakwaters

60 scuttled ships (blockships)

33 platforms Loebnitz

A complete Mulberry required 600,000 tons of concrete piers and 33 had 15 km of floating roads to transport people and vehicles on land.


Piers were created by combining the following elements:

the blockships, condemned and cast in situ ship

the bomb, metal boxes in the shape of a cross,

Phoenix caissons, huge concrete caissons.

Blockships are the first the first solution to form dikes artificial harbors. Cargos old warships, they are the first to cross the English Channel from Poole Harbour, where they were gathered. Thus, 56 ships will be positioned on June 7 at the five beaches for sunken hull exceeding 2 m at high tide.

The bomb, metal boxes with dimensions of 60 x 8 m, are manufactured in Portland. Towed across the Channel, they were interconnected on selected areas and acted as a breakwater off the artificial harbors. This bomb will cause a lot of damage during the storm from mid-June (see below).

The Phoenix caissons were imposing concrete caissons, a rectangular partitioned and inside shape. It was designed six models of boxes, the smallest weighing 1670 tons, the largest of more than 6000 tons with a length of 70 m, a width of 15 m and a height of 20 m. On site, these boxes were filled with water using valves that are opened in each of the compartments and resting on the bottom of the sea, only the upper part emerged from the waves, forming levees and discarded.

The 212 Phoenix caissons (both ports) were built in the Thames estuary and Southampton. The work was entrusted to private companies building as Robert McAlpine, Peter Lind & Company and Balfour Beatty which still exist today. Starting June 7, they were also towed across the Channel to the Normandy coast at a speed of 8 km / h.


Another technical challenge, wet docks away from piers were able to follow the tide, up and down. The engineer conceived of Pearson Löbnitz platforms 70 by 20 m, totaling 1,100 tons. These platforms coulissaient four steel 30 candles (the spuds), laid on the seabed. Hydraulic cylinders allow a clearance of 5 m. At Arromanches, seven platforms were linked together to form a platform 750 m long wharf connected to the mainland by two floating channels.

Floating channels

Ways floating called whales (whales) were designed to connect the dock to the shoreline. Designed by Mr. Beckett, metal bridges with a length of 24 m and a mass of 28 tons based on concrete floats 19 tons each. Thus, sections of nearly 150 m long, each composed of five bridges, crossed the Channel to be connected to each other before the Normandy coast. A total of 15 km of floating jetties was built. After the war, some of these bridges were reused to replace bridges destroyed by bombing in the interior.

Construction in England

From September 1943, over 300 companies were retained for the construction of the various elements, and of course several sites, even if congestion shipyards. 212 boxes, 23 docks and 15 km of track and will be joined by more than 40,000 people between October 1943 and May 1944. The Phoenix caissons were built in the Thames estuary and Southampton. After prefabricated Richborough and Southampton routes Whale join Selsey and Dungeness, to be assembled with the docks Löbnitz.

Both ports

It was planned two ports, namely:

Mulberry A (“A” for “American”), in front of Saint-Laurent-sur-Mer on Omaha Beach for Americans. He took office on June 16 but will be destroyed by the storm of June 19 to 21

Mulberry B (“B” for “British”) in front of Arromanches, for Anglo-Canadians, he took office on June 14.

Only Mulberry B will remain operational after the storm mid-June. However, the Americans will show a great sense of organization and will break records unloading cargo, ammunition, vehicles and men on the beaches of Utah and Omaha.

The storm of June 19 to 21

Ports were scheduled to go according to J-21 that is to say on June 27 and last for three months. But on June 19, a storm arose and lasted three days producing gale force 6-7 or 45-60 km / h dips two to three meters. The storm caused extensive damage on Mulberry A, the U.S. port facing Omaha Beach and on a smaller scale than, British, Arromanches. The U.S. port, the breakwater caissons were sunk in water too deep and blockships these old boats cast protection in the boxes were too far apart. So they could not prevent the swell entering the harbor and destroy the docks and assault landing. It was therefore decided to stop the construction and abandon the American port. It would be “cannibalized” to repair and improve the UK port was renamed Port Winston. It is estimated that the storm caused a deficit of 20,000 vehicles and 140,000 tons of supplies.

Actual usefulness of Mulberry

This port has often been put forward as having ensured the success of the Battle of Normandy and often touted as one of the finest examples of military engineering and logistics. Historians now relativize some role. 35-48% of the UK tonnage transited through the port of Arromanches between June 6 and August 31, and much less the first week: 12% to 19 June and 19.6% in early July. Americans although private port and without the use of Arromanches landed tons of 40% more than their Anglo-Canadian allies (10 000 tonnes a day against 6000). This reduces to 25% the total amount spent by the artificial harbor. A large-scale grounding at low tide large landing craft technique, a larger than expected possible use secondary ports such as that of Courseulles as taken in fair condition allowed these discharges. It was only after the war that the Allies took the view that from a logistical point of view, they probably would have happened to a particular port and the time and money spent on their construction could be better used in the war effort. But the existence of such a structure allowed the Allies to not focus immediately on taking port in the weeks following the landing contrary to what the Germans thought. Both ports have thus played an important role in the strategy Overlord.

The remains

Phoenix caissons:

Many are still visible today off Arromanches and others in England (two in the port of Portland, two cast Pagham and accessible at low tide, aground in the estuary of the Thames).

Whale pontoons also called “bridges Arromanche”

After the war, about 180  were reused for the passage of rivers inland. Thus,  a bridge crosses the Whale Noireau in the locality of the municipality of Bordeaux Saint-Denis-de-Mere in the Calvados since 1945

Whale a bridge crosses the Oise to Manicamp in the Aisne since 1946

Whale a bridge crosses the Eure in Pont-de-Ark in the Eure,

Whale two pontoons spanning the Ill in the town of Horbourg Wihr (Haut-Rhin) since 1947.

two bays Whale pontoon span the Meuse to Vacherauville (Meuse)

five sections spanning the Moselle on the secondary road D56, connecting the towns of Cattenom and Kœnigsmacker (Moselle), and

a span crossing the river Tasty Lime and another Saint-Nicolas Foussemagne in Belfort.


In the early 2000s, five pontoons Whale floating channel were found in a technical center of the Departmental Directorate of equipment to Esvres-sur-Indre (Indre). These pontoons were installed in 2004 in the municipality of Vierville-sur-Mer (Calvados), to form a bridge 130 m long.


The Case of the landing: “Operation Mulberry.”  Pedagogical work on the port of Arromanches created by François Rouillay, texts Remy Desquesnes, preface by Raymond Triboulet, Mak’it editions, 1984 (ISBN 2-905091-01-0)

Olivier Wieviorka, History of the Normandy landings. Origins in the liberation of Paris 1941-1944, Editions du Seuil, coll. The Universe, 2007 (ISBN 978-2-298-00542-4)

Alain Ferrand, Arromanches, History of a port, PERT editions, 2004, (ISBN 978-2-912925-07-7)

Jean-Pierre Benamou, the port of Arromanches Normandy 1944 editions PERT, Memory collection 1944 2004, (ISBN 978-2-912925-54-1)

Gerard Lecornu, Saving the port of Arromanches, Editions Hirlé, Q1 2006, ISBN 2-914729-42-1


Artificial ports of landing (The Mulberry Harbours) Gwenaël QUERE, 1994

Arromanches Mulberry operation, 90 ‘, DVD format, Publisher Sony-Music-Video, 2004, ref 2023229

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