If the Allies could not capture a major port, they would have to build their own. The British War Office began the planning and construction of two artificial anchorages and ports to support the upcoming Allied invasion of France. The Combined Chiefs of Staff officially approved the artificial port concept at Quebec in August 1943. The project was code-named mulberry. The Allies would fabricate the two artificial ports in England, tow them across the English Channel, and establish them off the French coast. Mulberry A would support the American invasion beaches, and Mulberry B would support the British beaches.
The prefabricated ports incorporated numerous components that had code names of their own. The first step in the process involved the creation of artificial anchorages known as Gooseberries. Engineers accomplished this feat by positioning and sinking a number of blockships on D day, 6 June 1944, to create artificial anchorages. Five such anchorages were created, two off Omaha Beach for the Americans and three off the British and Canadian beaches. The ships utilized were obsolete American, British, Dutch, and French warships and merchant vessels.
Two of the anchorages served as the foundation for the two Mulberries. The outermost breakwater consisted of bombardons, large floating constructions that were 200 feet in length, 25 feet across, and weighed 1,500 tons. These were located approximately 5,000 feet out from the high-water line. They enclosed an outer harbor, and 1,000 to 1,500 yards closer to shore, a row of sunken ships known as Corncobs and large concrete caissons known as Phoenixes created another breakwater to shelter the inner harbor. The floating and sunken breakwaters protected a series of piers, pier heads, and moorings for large vessels, such as Liberty ships, and smaller landing craft.
Plans called for Mulberry A to have three pier heads, two pontoon causeways, and moorings for seven Liberty ships and five large and seven medium coasters. It was to have a capacity of 5,000 tons of cargo and 1,400 vehicles per day. Construction began on 7 June 1944, with a planned completion date of 24 June. Construction proceeded rapidly. On 10 June, the engineers completed the Omaha Gooseberry, followed on 13 June by the Utah Gooseberry. On 16 June, the first landing ship, tank (LST) pier went into operation at Omaha, with one vehicle landing every 1.6 minutes. By midnight on 17 June, U.S. Navy engineers working on Mulberry A had placed all 24 bombardons and 32 of 52 Phoenixes, along with mooring facilities for two Liberty ships. They also had completed the western LST pier, with work on the eastern pier under way.
As that work progressed, construction on pontoon causeways at both beaches continued. The first and second pontoon causeway at Omaha entered service on 10 and 20 June, respectively. At Utah, the first opened on 13 June and a second on 16 June. The initial concept of the artificial port appeared to be proving its worth. Work on the British Mulberry B proceeded at a similar pace.
Unfortunately for the Allies, the worst Channel storm in a half century hit the Normandy coast on 18 June, halting all landing operations for three days and, more important, destroying Mulberry A and forcing the Americans to abandon the artificial port. The destruction of Mulberry A made the capture of the port of Cherbourg all the more important. Further, as feared, the German defenders put up a stiff resistance, and the port did not fall until 27 June and only after it had been effectively destroyed. The first Allied cargo did not arrive through Cherbourg until 16 July and even then only in small amounts. By the end of July, cargo arriving in Cherbourg constituted only 25 percent of the total arriving over the beaches at Omaha and Utah.
The great storm also seriously damaged Mulberry B off the British beaches, but it could be repaired. General Dwight D. Eisenhower, commander of the Supreme Headquarters Allied Expeditionary Forces (SHAEF), ordered that Mulberry A not be rebuilt and that parts from it be used to complete Mulberry B to the original specifications. When completed, Mulberry B became known as the Harbor at Arromanches. By October, the port enclosed 2 square miles of water and could berth 7 Liberty ships and 23 coasters at the same time. Intended only for use until French ports were repaired and put back into operation, the artificial harbor remained in service until closed on 19 November. By the end of December, disassembly had begun.
While the contribution of the Mulberries did not meet preinvasion expectations due to the destruction by the storm, the artificial harbors proved invaluable in the Allied supply effort. Fortunately for the Allies, DUKW amphibious trucks and LSTs proved more effective in moving supplies over the beaches than expected and were able to compensate for the shortfalls from the Mulberries. The combination of tonnage delivered over the beaches, through the Mulberries and through captured French ports, enabled Operation overlord to succeed, leading to the victory in France. The Mulberries were an engineering marvel that further demonstrated the Allied technical expertise and ability to turn resources into military power.
Steve R. Waddell
Bykofsky, J., and H. Larson. The U.S. Army in World War II: Transportation Corps Operations Overseas. Washington, DC: Center of Military History, 1957.; Hartcup, Guy. Code Name Mulberry: The Planning, Building and Operation of the Normandy Harbours. New York: Hippocrene Books, 1977.; Ruppenthal, Roland G. The U.S. Army in World War II: The European Theater of Operations—Logistical Support of the Armies. 2 vols. Washington, DC: Center of Military History, 1953, 1959.