War Winning Engineering: Mulberry Harbour and the D-Day invasion.
Creating two ports, each the size of Dover harbour, was no mean feat in wartime Britain, requiring innovation, tenacity, and hard work. In this online exhibition, the Royal Engineers Museum explores how engineering was crucial to the success of the Mulberry Harbours, as well as many other war-winning projects.
Explore the components that made up the Harbour by clicking on the image below, or scroll down to learn about the invasion and the Royal Engineers Museum’s collection.
How to get thousands of men and supplies quickly and safely into occupied France?
The solution: Engineering ingenuity combined with political will and detailed planning.
‘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.’
Churchill’s memo ordering the construction of the Mulberry Harbours from 30th May 1942. REM PA/61A/7. Crown Copyright Open Government Licence 3.0
On 30th May 1942 Winston Churchill wrote his now-famous memo titled ‘Piers for use on beaches’. It marked the start of one of the greatest engineering projects of all time, the Mulberry Harbours.
By 1942, German forces occupied or controlled most of Europe, from France to the Soviet Union, along with all the ports across France, Belgium and the Netherlands. In August of 1942, Allied forces mounted a deliberate but disastrous raid in some force against the port of Dieppe. Realising the impossibility of capturing a port, the Allies settled on an audacious plan to bring their own port for any future invasion of mainland Europe. Between 1942 and 1944, military and civilian engineers worked tirelessly to figure out the solution to Churchill’s demands.
Made up of Bombardon breakwaters, Corncob blockships, Phoenix caissons, Spud pontoon pierheads, Whale roadways, and Beetle pontoons, the Mulberry Harbours truly were war winning engineering. By the end of the war, they had enabled 2.5 million men, 1.5 million vehicles, and 4 million tons of supplies to enter Europe.
This cartoon map of Mulberry Harbour shows each element as literal interpretations of the codenames, with even the location of the harbour represented at the bottom. The berries are Mulberries, the golden arrow acknowledges ‘Arromanches’ and Gold Beach, and the bee ‘Mulberry B’, the second harbour. REM 8101.10. Francis Marshall CC BY-NC-SA 4.0
Did You Know:
In May and June 1944 ‘Mulberry’ and the names of all five invasion beaches appeared in the Daily Telegraph crossword. The British intelligence services worried that this was a sign of espionage, but the truth was a lot less exciting. Leonard Dawe, who compiled the crosswords, worked at a school next to a camp of US and Canadian soldiers preparing for D-Day. Their chatter was heard by the schoolboys and then by Dawe. He had no idea that they were top-secret codewords!
The elements of the Harbours were constructed in sites all around the UK, from Scotland to Kent, before being towed across the English Channel from D-Day onwards. The plan was to construct an American harbour, Mulberry A, on Omaha beach, and a British Harbour, Mulberry B, on Gold Beach. The other three invasion beaches, Juno, Utah, and Sword, would have Gooseberries installed, consisting of blockship breakwaters. The two Harbours were almost complete when, on D+13 (19th June, 13 days after D-Day), the worst storm in 80 years battered the Normandy coastline. When it was over on D+17 (23rd June), only Mulberry B was standing.
Designed to last only 90 days, Mulberry B was officially closed on 19th November 1944, D+166.
An aerial photograph of Mulberry B in use, with each element annotated. REM 23/891/5/2. Crown Copyright Open Government Licence 3.0
About the War Winning Engineering Exhibition
This online exhibition was created as part of ‘War Winning Engineering’, a project carried out by the Royal Engineers Museum between 2024 and 2026, funded by The National Lottery Heritage Fund. It explored engineering innovations of the Second World War, in particular the Mulberry Harbours. During the project we conserved and digitised thousands of technical drawings and plans in our collection, and showcased some of our extraordinary objects – including an original kite anchor – in our temporary War Winning Engineering: Planning an Invasion exhibition.
The MHP Plan series: A collection of 2800 engineering plans, 605 directly linked to the Mulberry Harbours, and the remaining relating to the engineering heritage of WW2, with a small number of those being post-war.
PA/120/2/3: Notes on the Construction of Mulberry Harbour in Normandy, June-July 1944.
M742: The Artificial Invasion Harbours called Mulberry. A Personal Story, by Sir Bruce White KBE.
M745: The Story of the Mulberries, written by Rear-Admiral Harold Hickling and Brigadier I.L.H. Mackillop
M285: R.E. Aspect of Operation Overlord D to D+30.
M746: Mulberry Harbour - Personal Notes by Those Taking Part, compiled by Prof. A.J. Harris
M1230: Conference on Wartime Engineering Problems. Papers including The Bailey Suspension Bridge and Mulberry Pierheads.
M752: Piers for Flat Beaches D.Tn. Scheme.
M737: Memorandum of Mulberry and Other Equipment showing Possible Post War Uses, Director of Ports and Inland Water Transport War Office
M1230: Conference on Wartime Engineering Problems.
M1154: Operation Pluto, including Development of the Hais Cable, by E.A. Beavis and Operation 'Pluto', by AC Hartley.
M1202: Bridging Wing. An instructional manual on the construction and installation of Bailey bridging.
To book a research visit to the Museum to these titles, or find out what else is in the archives, please visit the Museum Contact Us Page.