Rodman S Schools. World War II. Volume 15, Issue 2, July 2000.
Opinions vary as to the value of the artificial harbors that were placed off the D-Day beaches.
Of all the engagements of World War II, probably the most compelling was the 1944 Normandy invasion. The images of men in jeopardy on bullet-swept landing beaches are familiar ones, but behind the scenes of the battle is one of the most fascinating tales of the war: the preparation of two pre-fabricated harbors, a project which required secret military and civilian efforts of herculean proportions.
Called “Project Mulberry,” it was one of the boldest and most original conceptions in military history, aiming at supplying important support for the early phase of the invasion. To this day people argue over whether the prefabricated harbors contributed significantly to the invasion’s overall success. Some say they were absolutely critical; others claim that, in the final analysis, they contributed little.
Stretching from Denmark to Spain on the west coast of Europe was a large, professional German army commanded by the highly respected Field Marshal Gerd von Rundstedt. Rundstedt’s subordinate in Normandy was Field Marshal Erwin Rommel, well-known as the “Desert Fox” for his exploits in North Africa. The Allies believed that despite Rommel’s reputation, such an army could be defeated by a larger army, provided it had sufficient resources. Without the ability to disembark huge quantities of trucks, guns, tanks and other supplies continuously, however, the liberators would soon run out of the critical equipment needed to overwhelm and punch through the German defenses. Ports with docks, cranes and protected harbors were sorely needed. The invasion planners concluded that it would be unrealistic to pin their hopes on storming an operating harbor and seizing it intact.
So from the very beginning everyone knew that the problem of the lack of port facilities had to be overcome if the invasion were to succeed. The docking and unloading problem facing the D-Day planners centered on two requirements: first, the need to create a stable unloading area near the invasion beaches; second, the creation of a docking mechanism and a roadway for vehicles leading from the docks to the beaches. A major obstacle was the Channel tides. During the high-to-low tide cycle, the water rose and fell as much as 20 feet. Given the shallow slope of the beach, the water-line at low tide was a quarter of a mile from the high-water mark, exposing a wide stretch of bare sand.
The tidal currents also presented a problem. In the narrow Channel waters, heavy currents flowed alternately east and west parallel to the coast as the tide changed. In addition, the shore was fully open to the sea, and the water near the beach was known for its roughness. Navy men—even those experienced in unloading vessels in turbulent waters—were concerned.
During early phases of the planning, experiments were conducted to reduce sea-wave motion and to design pier heads suitable for the open sea. But there was no breakthrough in the creation of the overall harbor plan. Then one day, during a meeting on the problem, Commodore John Hughes-Hallett, a British Royal Navy planner, said, “Well, all I can say is, if we can’t capture a port, we must take one with us.” From that half-joking remark came the proposed solution to the harbor problem. In June 1943, all thinking, experimentation arid initial design work were organized under the official code name of Project Mulberry.
The overall design for Project Mulberry began with a massive breakwater to provide calm waters, something that could be installed in a few days. As difficult as it seemed, the designers conceived of a line of gigantic concrete blocks, placed end to end, and sunk into the mud just offshore from the invasion beaches. The floating blocks, which could be towed across the Channel from England, would be about 200 feet long, 60 feet high and 60 feet wide, with flat bottoms. Each of the blocks, which were code-named “phoenixes,” was thus about two-thirds the length of a football field and about as high as a five-story building, displacing about 6,000 tons—heavy as a good-sized ship. To ensure buoyancy, the blocks were subdivided into hollow, watertight compartments. The design called for them to be sunk at low tide in a line two miles long, approximately one mile offshore, in 30 feet of water. Even with tidal changes, at least 10 feet of concrete wall would protrude at all times.
The problem of crosscurrents was solved by placing a shorter line of phoenixes near the western end of the long breakwater, running at a right angle toward the shore. Thus the current flows would be hindered from providing a dangerous undertow.
Since there were several landing sites, planners decided they needed two such breakwaters, one off Omaha Beach, to be called Mulberry A, and one near Arromanches at Sword Beach, known as Mulberry B. Each required about 100 phoenixes.
Finally, there was the problem of unloading the LSTs (landing ships, tank) with their bow ramps on the shore. Theoretically, a fully loaded LST could roll ashore at high tide, unload and easily back off into deeper water. But because of the rapidly changing tide, a smooth procedure could not be counted on, and there was a high likelihood that a ship might be stranded for 12 hours by the tide cycle. Such a delay would severely reduce the amount of tonnage that could be unloaded.
To solve this problem, the engineers adapted the design of a mechanism developed in 1923 by Lobnitz & Co., an English firm experienced in dredging operations. It consisted of a large, horizontal platform held in place by four steel legs at each corner. The platform could be raised and lowered relative to the water surface. As conceived by the designers, it would bean ideal pier. Just inside the artificial breakwater, the legs could be driven into the mud and firmly anchored, Then, as the water level rose and fell with the tide, the platform could rise and fall, controlled by machinery within its steel hull—in effect, creating a “floating” pier.
According to the plan, when an LST tied up to the dock, the relative height of the dock could be adjusted so that vehicles could easily be driven off over the LST’s bow ramp and onto the pier. The adjustable pier head was given the code name “lobnitz.” Plans called for 23 of these devices to be used during the landing.
Then there was the roadway problem. Unloaded vehicles and supplies required a stable pathway from pier to beach. Designers chose to use a pontoon bridge design, unique in this case because of the sheer size—each bridge was to be approximately 3,000 feet long.
Each section would be an 80-foot highway truss—code-named “whale.” Once the trusses, which were supported by concrete pontoons, reached the beachheads, they were to be joined together to form the floating bridges. The plan called for seven roadways, three in the American sector of the invasion area and four in the British. At Omaha, in the American sector, for example, there were to be two truck roadways, each capable of bearing loads of 25 tons, and one roadway for Sherman tanks capable of carrying a tank’s full battle weight of 38 tons.
Even with this, the design for the harbors was still not complete. To ensure maximum calming of waves around the unloading area, designers decided further measures were needed. They conducted experiments to learn how swells could be broken up in deep water. By October 1943, it was decided that a successful strategy would require the addition of a floating breakwater anchored well beyond the coastal phoenixes in water too deep for any concrete box. To protect this part of the secret plan, the designers adopted deceptive terminology: the outlying breakwaters were referred to as “bombardons.” The name suggested that the breakwaters were somehow related to antiaircraft defenses—one of the many ruses used during the war to mislead Nazi intelligence. The bombardons were 200-foot long steel hulls, with 9-foot wide horizontal steel fins that stuck out laterally from the hull just below the waterline. Anchored well behind the line of phoenixes and partially submerged below the water’s surface, the string of 24 bombardons created a floating breakwater nearly a mile long.
Between the bombardons and the phoenixes, or line of concrete blocks, was a semi-protected area. The bombardons were believed capable of breaking seas tossed up by a force 5 wind (about 20 knots or 23 mph), and of reducing wave heights from 8 feet to about 3 feet. The planners argued that a second means of delivering cargo was therefore possible: Liberty ships would be able to anchor and discharge cargo into smaller amphibious craft under most summertime weather conditions.
Many were skeptical the Mulberry Project could succeed, doubting the ability of the hulls to quiet wave action to the extent calculated by the planners. They also pointed out that steel fins sticking out from the hulls could be very dangerous to tugs—they were underwater, out of sight and could easily slice open a ship’s hull. A further objection was that the bombardon plans called for the use of more than 20,000 tons of steel, mostly, one-quarter-inch plate. In wartime, steel is needed for weapons of all kinds and is a precious commodity. This objection, like the others, was eventually overruled, however, and the decision to divert a significant amount of steel for this controversial application is a mark of how crucial safe harbors were considered to be to the overall D-Day operation.
Allied leaders discussed Project Mulberry at the Quebec Conference in September 1943. It soon became clear that they needed to understand the engineering details. An urgent message was sent to London, and the engineering ream flew to Quebec to brief the military chiefs. After watching films and examining working models, the Allied high command approved the design, opening the way for the unique construction project to get underway.
Building the concrete-block phoenixes required large numbers of workers—at the peak of the project, more than 22,000 people. In addition to using already-constructed dry docks as building sites, 17 temporary basins were dug near the Thames River to hold the caissons during construction. The caisson construction consumed more than 545,000 cubic yards of concrete, 30,000 tons of reinforcing steel bars and 15 million linear feet of tubular steel scaffolding. When the phoenixes were ready to launch, the earthen barriers were removed, the river water filled the holes and the huge concrete boxes floated out to their parking areas at Selsey Hill and to a site about 80 miles east at Dungeness.
During the building phase, the military planners decided that more roadways were needed. They therefore increased the overall length of the whales from six to 10 miles, requiring a total of 60,000 tons of steel.
When the pier head was tested, the designers found that after the LSTs docked, their bow doors could not be fully opened. Because of the importance of the project and the time constraints placed on the building phase, the ships had to be modified rather than the pier. The entire Allied fleet of LSTs was altered as a result.
It also soon became clear that the total production of phoenixes was going to fall woefully short of the number required under the Mulberry plan. As a solution, the British turned to the old war horse, the merchant ship. In the early phases of the war, despite relentless German U-boat attacks, merchant ships had been critical to Britain’s defense. But priorities shifted when the United States entered the war, and Britain was not so dependent on its Atlantic shipping for survival. A percentage of the merchant fleet was therefore deemed an expedient substitute for phoenixes—not only worn-out hulks but also ships that had plenty of life left in them. Seventy-four hulls, code-named “gooseberries,” were to be sunk in a line alongside the caissons to form auxiliary breakwaters at Omaha and Sword beaches. Since the hulls were not as tall as the 60-foot-high phoenixes, they would have to be sunk in shallower water. The idea of sinking ships in a straight line was in itself a daring scheme, since when ships are deli berately sunk, they rarely end up in the desired position.
In just over eight months, as many as 45,000 British workers created two floating ports, consisting of more than 600 components, using over 2 million tons of steel and concrete, and costing about $125 million.
On June 6, 1944, Allied troops began their fateful scramble across the Normandy beaches. Early the next morning, D-plus-1, tugboats began a slow journey across the Channel, towing huge chunks of concrete and other Mulberry components. Each phoenix had compartments capable of housing up to 30 men and was equipped with one or two anti-aircraft guns—only a token defense. A typical phoenix’s complement that day, however, was only six persons: a four-man gun crew and two sailors or Seabees. Two phoenixes sank on the way—one by a German motor torpedo boat and one possibly destroyed by a floating mine.
An officer of Britain’s Royal Navy, Captain Dayton Clark, was in charge of installing one of the floating ports. He had chosen the Mulberry A site at Omaha Beach. He had to depend on 50-year-old depth soundings that more recent—but less sophisticated—tests conducted prior to the invasion had found to be reasonably accurate. The gooseberries were installed first, followed by phoenixes, the lobnitz piers and then the whales. The bombardons were to be placed at the same time the other harbor components were coming together. Despite intermittent enemy artillery fire, Clark had buoys set out to mark where the phoenixes and gooseberries were to be sunk.
The first Liberty ship, James Iredell, approached the phoenix line about a half mile from shore. The crew fired explosives in her belly and felt the old ship slowly settle in the sand. As other ships were put in position to be sunk, enemy fire increased. Some of the men handling the ship-sinking operation later speculated that German defenders on shore-seeing ship after ship shake with internal explosions-must have considered their marksmanship better than usual that day. Following the Liberty ship, a large battleship, HMS Centurion, which had been moving toward shore, swung slowly to starboard, as if to position her 13-inch guns broadside to the enemy, and suddenly creaked upward slightly to sounds of muffled explosions inside. She then sank onto the sands. Her crew of about 70 got off without injury.
Although the original Mulberry plan for Omaha Beach called for three whale roadways, during the crossing some of the 40-ton pontoons were damaged, allowing enough for only two roadways. Clark had to face the question of whether 25-ton pontoons, intermixed with the larger ones, would support the 38-ton weight of a fully battle-equipped Sherman tank.
That critical decision eventually fell to a veteran American salvage man, Captain Edward Ellsberg. After a day and night of anxious measuring and calculating, he decided that the bridge would hold up, provided the tanks were spaced far enough apart. Ellsberg later put his life on the line in support of his decision by leading on foot the first Shermans along the roadway toward the beach. As a tank approached the first 25-ton pontoon, it began to sink deeper and deeper into the water. When the tank moved directly onto the float, Ellsberg thankfully saw that a small portion of the pontoon was still above water, allowing a narrow margin of safety.
On June 8, the first phoenixes arrived at Omaha. They were not in position until two days later because of heavy enemy fire. Within four days, 32 were in place, providing a useful breakwater. At Mulberry B, placement began on the 10th. By the 18th, 25 units had been installed. (One had been accidentally hit by a tug, however, and forced out of position.)
During the first few days at Omaha, the surf and waves in the unloading area quieted. This allowed the big LSTs to run directly up onto the beach for unloading. They could then wait for the next high tide to back off and move away. Because of this unexpected bit of luck, by D-plus-5, off-loadings at Omaha reached about 7,000 tons per day. When fully operational, the harbor would need to handle 8,000 tons per day, but deliveries at that level of tonnage were not expected until D-plus-12.
Clark had been given 12 days to finish the first whale roadway. Many had thought it could not be done in 30 days, but by working 24 hours a day, installers finished their work by D-plus-9, three days ahead of schedule.
At 1630 hours on June 16, Mulberry A received its first LST at a lobnitz pier. Within 38 minutes after the ramp door dropped, 78 vehicles rolled ashore. During the first two days, 11 LSTs docked, taking one hour on average to discharge, compared with the 10 to 12 hours that would have been needed if they had been run up onto the beach.
By the next day all the Mulberry A bombardons were in place. By June 18, D-plus-12, the second roadway was completed, letting two streams of vehicles, tanks and trucks move to shore at the same time. Given the amount of unloading taking place directly onto land, the Mulberry operation was now in fact a major invasion port. The numbers are truly impressive. Through June 18, onto the beaches poured 197,400 troops, 27,300 vehicles and 68,800 tons of supplies, about 40 percent of this cargo arriving via the Mulberries. The Normandy beaches became the most active ship off-loading site in Europe, with a capacity greater than any other port in northern France.
Despite the early success of the harbors, sailors working around Mulberry A noticed that the seas were becoming rougher. Navy officers managing the port had received a report that three small amphibious craft had swamped just outside the breakwaters. The wind had picked up to 20 knots, puzzling forecasters, who had predicted a few days of good weather. By the morning of the 19th, wind speed had reached 30 knots, and it was obvious to all that a storm was coming. Wave heights reached 7 feet. Virtually all unloading came to a halt. At high tide, and with an onshore wind, the sea rose 10 feet higher than normal and began to wash over the tops of the phoenix breakwaters. The anti-aircraft gun crews were evacuated. What made news of the approaching storm so ominous was that it was coming at the same time as a new moon and a period of maximum spring tides. Traffic was halted on the wildly bouncing floating roadways.
Some smaller craft, unable to leave the harbor area, tried to beach themselves. Others, attempting to anchor, soon ran into difficulty. In most cases their anchor lines quickly snapped in the crashing waves. The area around the beach became crowded, as more and more craft tried to find refuge on the beach. The wind and pounding surf pushed the boats toward shore, and they began to scrape violently as they tossed and heaved. Soon steel hulls were crashing and crunching together, smashing into scrap. Hapless men who did not manage to free themselves from the boats were crushed and mangled in the mass of grinding steel.
Five LCTs—landing craft large enough to hold four tanks, each about 150 feet long—crashed into the eastern roadway. Given that battering, some of the whales’ pontoons sank and others were tipped open. Without pontoons, sections of the bridge sank in the water. Other parts were twisted sideways, with pontoons pointing up in the air and sections of trusses warped or severed.
The next day, June 20, the wind lessened. At low tide, Seabees were able to pull some of the loose LCTs away from the roadway. Later the gale increased again, and at high tide craft began piling into the bridge again.
During the day, as the waves increased in height to 8 feet or more, the bombardons—the large steel hulls floating in the outer harbor—began to tear free of their moorings and became gigantic sledgehammers as they drifted into the line of phoenixes. As the waves rose and fell, the massive hulls, surging in and out, began pounding the sides of the concrete blocks. The battering continued as the tide fell, gouging out large chunks of the walls. Now at high tide the inner harbor was unprotected from the open sea as waves rushed through the openings in the breakwater.
The storm continued into June 21, its third day. The winds abated somewhat, decreasing from 26 to 17 knots, with seas remaining at 8 feet. The scene at the beachhead was one of gloom and destruction. At some points, wrecks were piled as much as six deep against the shore. Between Sword and Omaha, more than 300 craft were destroyed beyond repair. The weathermen later described the storm as the worst to strike the coast in 80 years.
Nevertheless, unloading had continued during the storm. At its height naval officers had considered shutting down the anticipated harbor. When told that the port was about to be shut down, Lt. Gen. Omar N. Bradley refused to believe it. The various commanders of the 12th Army Group sent a few aides to investigate and get things moving again.
The harbormaster explained to the stunned aides that the only way to get supplies to shore, considering the state of destruction in the harbor, was to bring the small coastal steamers, with ammunition, inside the gooseberry breakwaters at high tide and strand them on the beach. Then, at low tide, trucks could be run up alongside to unload the ships.
The Navy people were halfhearted in their suggestion because they realized that the ships would suffer great damage and might be unusable after just a single unloading. When the aides sent this information back to Bradley, his reply left no misunderstanding of his position: Either take the chance on the damage to the ships or face the reality of large troop losses, or at the very least a slowdown in the drive to Cherbourg. Bradley wanted the ammunition without delay. So while the storm raged around them, the Navy brought the steamers in, beached them, and the unloading began. During the next two days of the storm, more than 1,500 tons of ammunition was offloaded and delivered to Bradley’s hard-pressed men as they continued their assault on the approaches to the important port of Cherbourg.
The storm dissipated slowly, and normal traffic in and around the Channel resumed by June 23. That day, despite the wreckage all around, 10,000 tons of cargo was unloaded, about 1,000 tons more than the port had handled on any previous day. The next day the total was 11,500 tons. On June 26, an amazing 14,500 tons was delivered. This was nearly twice the 8,000 tons required by the invasion planners.
Captain Clark and other harbor workers were now anxious to assess the damage at Mulberry A. Seven ships of the gooseberry breakwater had been smashed or broken up. Large holes had been knocked in the walls of the phoenixes. Some had been broken open by the pressure of the waves. About 20 had been damaged or destroyed. During the storm, a few phoenixes were still in tow across the Channel. Clark ordered them returned to England, but the tugs could nor make headway against the wind and seas, and the caissons were scuttled and sunk where they were. The two whale roadways were now twisted and partly submerged. About 21 bombardons were destroyed. Even so, there were sufficient remaining structures to provide water smooth enough inside the harbor for small craft to move about easily. Seabees brought in bulldozers to push the wreckage away, and soon the beachhead was clear.
After a brief inspection, Clark determined that a sufficient number of parts could be recovered to repair at least one whale roadway, and he requested permission to begin repairs at Mulberry A. On the advice of others—including some who were hostile to Project Mulberry—the naval commander at Omaha, Admiral Alan G. Kirk, refused his request. Kirk had been told that Cherbourg might be ready for Allied use in a few days (it actually required another three months to make Cherbourg operational again). He also understood that Mulberry B had suffered much less damage, and some argued that that undamaged pieces of the Omaha installation could be used at Mulberry B. The only repair work authorized for Omaha was patching holes in the phoenixes.
Clark had worked under tremendous pressure for more than two weeks with very little sleep and was devastated by this refusal. He left for England and was hospitalized, suffering from physical and emotional exhaustion.
Even though crippled, Mulberry A, through the determined efforts of Allied soldiers and sailors, kept operating above its expected capacity, sometimes shipping 16,000 tons in a day. As larger ports such as Cherbourg and Antwerp, Belgium, were liberated, Mulberry A at Omaha was finally closed in the fall of 1944. The harbor at Mulberry B, Sword Beach, equipped with spare parts from Mulberry A, operated until that November.
By late December, dismantling of the phoenixes began. Some were towed to Walcheren, in Holland, to repair dikes damaged by British bomber raids. Girders from the whale roadways were used to repair French bridges. The rest of the equipment was left to disintegrate in the sea where it had been placed. Even though intended to have a useful life of only a few months, the strength of the phoenixes is such that to this day, from the beaches of Omaha and the cliffs at Arromanches, they can still be seen as great gray shapes looming up from the seabed.
The building of the Mulberries was one of the greatest military engineering achievements in history. Some have compared their conception and use to the feat of the Persians crossing the Dardanelles on a bridge of boats in 480 BC. But to what extent did Project Mulberry help win victory in Europe?
Some argue that the Mulberry construction program diverted labor and materiel that could have been better used otherwise in the war effort. The use of marine dry docks did slow down repair and maintenance of ships, even though Mulberry was carried out during a slow period of actual ship construction. There is little doubt that production of some types of weapons and other materiel was reduced because of Mulberry’s heavy demands on steel.
And then, some ask, how effective were the fixed and floating breakwaters? The general consensus now is that the phoenixes should have been placed farther out to sea, eliminating the need for the bombardons. From postwar experiments, engineers learned that floating breakwaters like the bombardons are inefficient in breaking up waves. The large amount of steel used in them probably could have been better used elsewhere. The gooseberries, on the other hand, made no demands on war production and did not involve using tugs (which were scarce at the time), and their placement was reasonably effective. The whale roadways proved too fragile. About 40 percent of the sections were lost on the cross-Channel run. As for the pier heads, the problems with that element of the project resulted from their complicated design. At Arromanches, only about 15 percent of the supplies were discharged through the pier heads. Ships with draughts greater than 24 feet could not berth alongside it. Given the number of landing craft tha t finally became available, many feel that the pier could have been omitted.
Senior Allied military commanders and other leaders ultimately praised Project Mulberry. Major General Frederick de Guingand, chief of staff to British Twenty-first Army Group commander Bernard Montgomery, said that without the insurance of the artificial harbors it would have been wrong to have undertaken the D-Day invasion. Overall Allied commander Dwight D. Eisenhower was grateful for the Mulberries and said, “Mulberry exceeded our best hopes.” British Air Marshal Sir Arthur Tedder commented, “Indeed, the whole question of the invasion of Europe might well have turned on the practicability of these artificial harbors.”
The concept and the capability of Mulberry gave the Overlord planners the freedom to choose a landing area strictly based on optimal military needs. Royal Navy Captain Harold Hickling, chief of staff to Rear Adm, W.O. Tennant, who had overall charge of the construction and assembly, said that Mulberry was only 15 percent of value in the landings. The British report to the chiefs of staff states that it is probable the invasion would have been successful without it. General Walter Bedell Smith, chief of staff to Eisenhower, strongly disagreed. “That 15 percent,” he said, “was crucial.” Author Chester Wilmont has said, “Psychologically, it gave the Allied High Command a degree of confidence without which the venture might never have been undertaken.”
From the German perspective, Albert Speer, Reichsminister for armament and war production, gave another opinion. He said that “by means of a single brilliant technical device,” the Allies bypassed the Atlantic Wall and made the German defense system completely irrelevant.
Whichever view history may favor, Project Mulberry gives unmistakable evidence that, in war, the side with the materiel resources to support its troops and the will and spirit to undergird and drive that support is the side that wins.