The Mulberry Harbours of Normandy

When the sea goes out in Arromanches-les-Bains, a small village on the coast of Normandy in northwestern France, the large concrete pontoons that lie half submerged in the salty waters expose themselves in their entirety. These concrete structures played a significant role in the history of Europe, facilitating the landing of thousands of Allied troops and their equipment on the beaches of Normandy during Operation Overlord.

Mulberry Harbors Arromanches-les-Bains

Mulberry harbour ruins in Arromanches-les-Bains, Normandy, France. Photo: Shandarov Arkadii/Shutterstock.com

The Allied invasion of Normandy was a massive and daring operation that required the movement of over a million troops and tens of thousands of metric tons of military equipment, including weapons, ammunition, vehicles, tanks, as well as food, clothing and other supplies. Offloading that much equipment from ships onto the beaches required a harbour, but Hitler had already secured all important harbours along the Atlantic coast, building a wall of coastal fortresses stretching from Scandinavia to Spain. This wall of defense proved impossible to penetrate, as the failed invasion attempt at Dieppe on August 1942 showed. Following the failed raid, Vice-Admiral John Hughes-Hallett suggested that if a working port could not be captured on the French coast, then one should be taken across the Channel.

The idea of a temporary, floating harbour—called Mulberries—gained immediate support from Churchill. Churchill himself had floated such an idea back in 1915, but the concept was never explored. On 30 May 1942, Churchill issued a brief and brutally straight to the point memo, describing the requirements for the Mulberry harbour system. The memo read:

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.

Mulberry Harbors Arromanches-les-Bains

The Mulberry artificial harbour off Arromanches in Normandy, September 1944.

The Mulberry harbour system consisted of many components. First, a series of breakwaters were created by first sailing old ships into place and scuttling them. Next, came several huge concrete caissons six-stories high, codenamed “Phoenix”, that were towed to Normandy and sunk into place to reinforce the scuttled ships. With a sturdy breakwater in place sheltering the shore, pontoon piers were floated and a flexible road was laid over them. Altogether, over 400 towed component parts were used to created two Mulberry harbours, each containing multiple piers, one at Omaha beach for use by the American invasion forces, and another at Arromanches, for use by the British and Canadian invasion forces. By mid-June the Mulberries were almost ready when a terrible storm, the worst to hit the Normandy coast in 40 years, destroyed the American harbour leaving the Mulberry harbor at Arromanches the only functional one. Over time the harbour came to be known as Port Winston, after Winston Churchill.

In the months following D-Day, Port Winston was used to land over 2.5 million men, 500,000 vehicles, and 4 million tons of supplies, providing much needed reinforcements in France.

Even Albert Speer, Hitler’s favorite architect who designed Germany’s defenses, praised the Mulberry harbor. After the war, Speer said:

To construct our defenses we had in two years used some 13 million cubic meters of concrete and 1½ million tons of steel. A fortnight after the Normandy Landings, this costly effort was brought to nothing because of an idea of simple genius. As we now know, the invasion force brought their own harbors, and built, at Arromanches and Omaha, on unprotected coast, the necessary landing ramps.

Remains of the Mulberry harbour are still visible today from the beaches at Arromanches. In addition, several “Phoenix” caissons sank while being towed and can be seen at places around the UK, such as in Thorpe Bay in Southend-on-Sea, at Pagham in West Sussex, and Portland Harbour in Dorset, to name a few.

Mulberry Harbors