In order to unload the vast quantities of cargo needed by the invasion forces without having to capture – intact! – one of the heavily defended Channel ports (a lesson of the 1942 Dieppe Raid), the Allies set up prefabricated marinas, code-named Mulberry Harbours, off two of the landing beaches. A total of 146 massive cement caissons were towed over from England and sunk to form two semicircular breakwaters in which floating bridge spans were moored. In the three months after D-Day, the Mulberries facilitated the unloading of a mind-boggling 2.5 million men, four million tonnes of equipment and 500,000 vehicles.
Today, Arromanches-les-Bains is an important D-Day stop for the remains of the Mulberry Harbours caissons visible in the waters and the exhibits at the Musée du Débarquement, dedicated to the history of the artificial harbours and their significance in the war effort.