With German forces heavily fortified along the French coast and all French ports in mid-1944 during World War II, the Allies were faced with the difficult problem of how to unload all the troops, weapons, ammunition, fuel and other supplies at the heads of beach of normandy British naval strategists envisioned building two massive artificial harbors, code-named Mulberry, one at Saint Laurent sur Mer (Omaha Beach) for American forces and the other at Arromanches (Gold Beach) to support American forces British and Canadian, while carrying out the largest maritime invasion in history.
Engineering approach
The developed system included fixed breakwaters of two types, floating breakwaters and piers with floating pier layers. Each Mulberry featured a 6,500-foot-long breakwater running parallel to the shore, 4,500 feet offshore, composed of open concrete “phoenix” boxes: 200 feet long, 60 feet wide, and 60 feet high , each weighing up to 6,000 tons. A second set of phoenix 1,600 feet long was placed at right angles to the beach for additional protection from wave action. Each phoenix housed a 40 mm anti-aircraft gun. Thirty-nine phoenixes were installed in each port. They were built in secret by 19 British construction companies in dry docks and tidal basins along Britain’s south coast.
Flanking the Phoenix breakwater was an additional 6,500-foot-long breakwater called “Gooseberry,” consisting of 14 older merchant ships and an old battleship, towed into position and sunk with explosives. Her superstructures protruded from the water and her anti-aircraft guns were manned, aiding in the defense. Parallel to the shore and 3,000 feet beyond the Phoenix breakwater was a floating breakwater consisting of 24 steel units, cruciform in cross-section, extending 6 feet above the surface, to break the action of the waves.
Inside the sheltered anchorage formed by the inner breakwater were three parallel piers extending 3,200 feet from shore, composed of 100-foot-long steel rebar sections supported by pontoons of anchored concrete or steel. Each pier carried a 10-foot-wide steel deck roadway. The docks connected to wharves known as Loebnitz docks, floating steel platforms stabilized by spikes, where landing craft could unload vehicles and cargo. Spinners were not intended to support the full weight of the pier heads, but to carry enough load to anchor it and keep it stable; an arrangement of pulleys and cables and electric winches raised and lowered the pierhead as the tide came in and out. The Loebnitz piers were chosen from four competing prototypes tested in Wigtown Bay in Scotland, chosen because the tides there were similar to those in Normandy.
The complete port construction sequence was to be 18 days after D-Day, June 6, 1944. Most of the Phoenixes were towed across the English Channel, positioned and sunk within the first week. United States Navy Construction Battalions (Seabees) manned the Phoenixes, pier heads, and pier sections while under tow across the English Channel and managed their installation.
At the same time, three dozen jury-rigged “Rhino ferries”—groups of barges tied together and equipped with pontoons and outboard motors—carried 300-ton loads to shore. Each Rhino was up to 42 feet by 176 feet, capable of carrying 30 or 40 vehicles.
For the first two weeks after D-Day the effort went well, but nature had other plans. A storm surge from June 19-22 wrecked the Omaha Beach facility beyond repair. The Mulberry complex at Gold Beach suffered less damage as it was located in shallower water and protected by a rocky bank.
Despite the damage to Omaha Beach, between the intact Mulberry Harbor at Gold Beach and the Rhino ferries working at full capacity, the supply effort was successful. The Rhinos alone transported 16,000 vehicles to the ground in Omaha in the first ten days. During her ten months of service, the Mulberry at Gold Beach channeled more than two million troops, four million tons of supplies and half a million vehicles onto French soil.
Details of these artificial harbors were subject to strict military censorship, which was lifted in October 1944. ENR published a brief article that month, followed by a full eight-page account in the December 28 issue of 1944
