D-Day

Two harbors and a ship

Seventy-five years ago young Americans and their Allies took a big gamble with the largest invasion force ever assembled. On 6 June 1944, they stormed ashore to gain first a toe-hold, then a foot-hold, and then more on the European continent and bring the ground war to Nazi Germany.

While their actions and sacrifices cannot and should not be minimized, their tenuous clutches at the beach and later their forays through the boccage of northern France could not have be accomplished without support in additional men and material. Much logistical planning—some have said even more so than that of the invasion—occurred in the months leading up to the landings.

One of the primary concerns of the planners was that there were few quickly obtainable ports in the north of France. Cherbourg was captured early, by the end of July, but its port facilities had been comprehensively destroyed and booby-trapped. Antwerp, Belgium, was captured on 4 September, but its wasn’t opened until the end of November after the Germans were pushed from its approaches. Boulogne and Calais were not opened until October and November, respectively. So without the prospect of decent port facilities, planners decided to bring their own.

Two synthetic harbors—named Mulberries—were planned for the Normandy beaches. Mulberry A was to be set up off the American’s Omaha Beach and Mulberry B was created for the British off Gold Beach. These had to accommodate the large tidal fluctuation on the beaches while providing a minimum of 18 feet of water for supply ships and transports and direct offloading to the shore. The solution was a set of floating piers connected to shore by a series of floating steel bridge segments.

The Mulberries consisted of a number of literally moving parts—including curiously named Corncobs, Gooseberries, Bombardons, Lobnitzs, Phoenixes, Whales, and Beetles—all of which required time for planning, design, construction, movement into position for the invasion. Construction consisted of 23 Lobnitz pierheads, 10 miles of road bridge comprising 660 80-foot spans (Whales), 670 floats (Beetles) to support the bridges, 8 shore ramps, 50 Bombardon floating breakwaters, 61 blockships (Corncobs), and 213 concrete Phoenix caissons. In all, 210,000 tons of steel and one million tons of concrete were used in the construction.

Three different types of breakwaters were provided to shelter the piers, bridges, and ships.

Bombardons were farthest from the beach and were connected to each other by hemp ropes and anchored to form a mile-long deep-water breakwater for ships to anchor as they waited their turn to unload or the tide to be right. These curious 200-foot-long by 25-foot wide and tall 1,500-ton objects were used in water too deep for the other breakwaters to function. They were hollow watertight steel constructions in the form of an equal-armed cross. In the water they floated with the horizontal arms just beneath the English Channels surface. Omaha used 24, while Gold had 26.

The second tier of breakwaters was constructed from concrete caissons—called Phoenixes—of six different sizes, sunk in water of 5.5 fathoms or less, displacing between 6,044 and 1,672 tons. These were designed and built to provide the Mulberry’s primary protection.  The Phoenixes—the largest 204-feet long and 56-feet wide—were sunk in position end to end. Mulberry A was to have 47. They got their name from the fact that after construction they were sunk and then later refloated for the invasion.

The third tier, called a Gooseberry, was placed in relatively shallow water—2.5 fathoms or less—to provide shelter for smaller craft. Each consisted of a number of Corncobs, blockships prepared in Scotland by cutting holes in bulkheads of surplus ships and placing scuttling charges below their waterlines. Gooseberries, numbered 1 through 5, were assembled off each of the five invasion beaches. The number of ships in each varied by the needs of the beach. In number order from Utah (10 ships) were: Omaha (15), Gold (16), Juno (11), and Sword (9).

The harbor facilities consisted of floating pierheads connected to the shore by a system of floating bridges and roadways. The Lobnitz spud pierheads were 1,760-ton barges 200-feet long by 60-feet wide, which were positioned and anchored to the seabed by four 89-foot long legs—called spuds—at each corner. When positioned, the spuds were lowered to the sand and forced down until they could move no further. This firmly anchored the pierhead and allowed it to ride up and down the spuds with the movement of the 24-foot tide. Ships unloaded their cargoes directly to the pierhead.

The pierheads had to be positioned far enough from shore so that they could be used by ships at low tide. Thus, they needed similar floating roadways. The answer was found in the Whales and Beetles.

Whales were 80-foot-long steel girder bridge sections supported at both ends by floats called Beetles. The beetles accommodated the tidal fluctuations and provided a firm base for the bridges when the tide was out. Expansion whales were inserted in the chain at intervals and connected the chain to a pier. These adjusted for the change in length as the tide rose or fell.

At Omaha, the task of assembling the Lobnitz, whales, and beetles was assigned to the 108th Naval Construction Battalion of the 25th Naval Construction Regiment. They began their work on 9 June and received its first ship— LST-342—at 1400 on the 16th.  

Over the next 3 days, 15 LCTs and 22 LSTs delivered 1,168 vehicles to the beach until a nor’easter from 18–22 June—the worst June gale in more than 40 years—destroyed the pierhead and bridging units. They were not placed back into service after the storm.

The gale wreaked havoc with the American Mulberry while the British port fared much better. Some reports indicate that the U.S. facilities were not as well anchored as the British, but what was more significant is that Gold Beach had a natural protection in the Calvados reef. Because a number of Mulberry A’s sections were lost in the Channel during the storm, the American Mulberry was abandoned.

Portions of A were salvaged and used by the British for what they now called “Port Winston.” It remained in use for a full six months until the opening of the port of Antwerp.

How effective were the Mulberries?

The Americans were not very impressed. While their loss of its facilities to the gale may color this thinking somewhat, numbers don’t lie. The Yankees—by design at Utah and by chance at Omaha—were forced to land their reinforcements and supplies primarily by LSTs.

At the American beaches, 6,614 tons of cargo was landed in the first three days. A month later, they handled 9,200 tons. A month after that, they were off-loading 16,000 tons per day. The Mulberry harbors, however, provided less than half the total even on good weather days from the start.

Average Daily Tonnage of Supplies Landed
Beach/Port	D+30	D+60
Omaha	1,200	10,000
Utah	8,000	6,000
Total U.S. beaches	9,200	16,000
Mulberry B	6,750	6,750

Planners had obviously underrated the capacities of open beaches and the utility of the LST. The tremendous tonnage capacities developed at the American beaches must have been one of the most surprising and welcomed features of the entire invasion.

Landing Ship, Tank (LST)

Arguably the most important ship type involved in Operation Neptune, these ships were among the most robust and versatile types put into service during the war. Their enormous capacity—each could transport an equivalent of 18 M4 Sherman tanks, 160 troops, and an LCT (landing craft, tank)—combined with the ability to put equipment and troops directly on a beach made them invaluable. Further, despite being called by irreverent crewmembers as “Large Slow (or Stationary) Targets,” they suffered few losses throughout the whole war—26 to enemy action and 13 to accidents and weather—compared to their number and wide-spread heavy combat operations.

Displacement	1,625 tons
Length	328 feet (overall)
Beam	50 feet
Draft	8 feet fore; 14.3 feet aft (full load);
	2.3 feet fore (unloading)
Speed	11.6 knots
Armament	8 40mm (some had 1 5-inch)
Complement	110