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"This project is so vital that it might be described as the crux of the whole operation. . . ."
— Memo to the First Sea Lord from Plans Division, Admiralty
Quoted on page 1, Operation Neptune (ON 16)
Mulberry released the weary military planners from a forbidding deadlock that had stalled them for months, the thorny problem in any sea‑borne invasion — the necessity to capture a port. In sheer intellectual power the idea had brilliance. It set aside the classic war problem of capturing a port by creating a new problem, building a port.
A fact which the ancient sea god himself, trident in hand, created, however, made the swift and sure execution of the Mulberry idea a matter vital to the whole survival of the invasion forces. In every sailing direction or coast pilot one can read the simple words, "The English Channel is seldom p35 calm." These words become more true as one closes with the French coast, for there the deep tidal currents grow stronger as they sweep around the headlands, then fan out into the bays beyond.
In the area selected for the assault, the Cotentin Peninsula, the shallow Baie de la Seine is laced with strong currents, up to three and four knots. This shallow bay offers waters quickly responsive to any strong wind. It is under these conditions that short steep seas quickly build up, as any sailorman will instantly recognize.
It is because this extra hazard of nature was boldly accepted, with Nature an adversary as well as man, that the concept of Mulberry became rather godlike in its reach and its daring.
It took the courage and literary imagination of a Winston Churchill to foster the idea that grew to be Mulberry. It needed and found the least conventionally minded group of planners, the men in the plans division of Lord Mountbatten's Combined Operations, to begin to surround the idea with the fabric of engineering feasibility. After that it took many men and many months before even a plausible chance of achievement appeared. One might truly say that, even at the final stage of actually mounting the operation on D‑day itself, those in command of Mulberry, those who knew most intimately the hazards, would have refused to gamble on better than a remote chance of success.
The Mulberry project called for the building in the U. K. of elements to form two complete harbors — breakwaters, piers, and bridging leading to the shore; then on D‑day, to tow these units across the English Channel and set them up on the open beach under assault conditions. Each harbor p36 was to be the size of Dover. Completion was to be in fourteen days or less. Dover, itself a man‑made harbor, under peacetime conditions took seven years to build.
However seemingly impossible of achievement to ordinary construction engineers, Mulberry did avoid the really impossible and bloody alternative — the capture from the sea of Le Havre, Rouen, Cherbourg, or a port in the Pas de Calais.
For those whose minds persisted in the classic mold of attacking an established port, the Dieppe Commando raid with its tragic history was there to ponder.a
The gunfire that flamed out of Cap Gris Nez with the passage of every coastal convoy through Dover Strait was there to see almost any night.
The overlapping arcs of fire from Cherbourg to Barfleur, to Le Havre, to Gris Nez were deadly in their saturation pattern. Any destroyer captain from Portsmouth could quietly trace out these arcs with his dividers on the Channel chart.
Beyond this blaze of intensely fortified coastline west to the Brittany ports of Brest or St. Nazaire, at the Loire's mouth, fighter air cover could not be provided from British air bases. Furthermore the shore fortifications there were hardly less formidable, for these western ports were the principal German submarine operating bases with immensely thick concrete fortifications. A ten‑ton bomb could barely dent their roofs. It will be remembered that later in the war, after the invasion, eighteen battalions of artillery attacked Brest from the land side till the earth shook miles away under the Channel. Yet Brest resisted nearly to the end.1 Those p37 mad Germans secure in their bastions did not capitulate for months.
This serves to demonstrate the severity of the conditions that demanded and received a new concept in the annals of warfare — the virtue of attack across the open beaches with the accompanying cool assumption of man's ability to create the sheltered waters of a natural harbor, with the piers and floating roadway structures over which tanks, trucks, men and stores could roll by the hundred thousand.
Aside from the possibility of such a plan as Mulberry, the final advice of the German General Staff to Hitler was correct: "Hold the ports and we will hold the continent of Europe."
In the eager thirst for more information about the details of Mulberry even the most informed senior officers of the Operations Room were left frustrated. Digging through the many planning papers now gives us a far better chance to put the whole story together than was possible for any of the Twelfth Fleet staff in 1943. But, even today, one is thwarted by the burned secret files and the tight grip of ultra secrecy that was clamped on the project from the start.
Little writing on the subject of Mulberry has appeared since the operation, for some obvious reasons. Military security2 even after the invasion in 1944 was so strict that on 5 July this order came from Eisenhower himself:
"Vital still that secrecy be maintained in regard to Mulberries. There must be no release to the press without supreme commander's authority."
Still other perhaps more subtle factors have prevented a p38 more extensive development of the facts, particularly in the United States.
On the American side, planning and installation was a U. S. Naval responsibility. But the top naval command until the tows were actually at sea was British. The construction of piers and breakwaters in the U. K. was British and, on the whole, was beyond British resources. While many great British-American friendships grew up as the project progressed, one is compelled in honesty to say also that ugly and heated conflicts arose. Not all the fire in them has died out yet, even after these many years. In this atmosphere, some who had knowledge were reluctant to speak or to reveal certain papers.
The central concept of Mulberry, as the premise on which the whole invasion of Europe rested, deserves better than this narrowness of view. So, accepting some gaps that must forever haunt a historian, made more profound by shrouded silence that is deliberate, by scattered records and lost files, from such records as do exist and such personal recollections as are available, the exploration of the beginnings of Mulberry requires the fullest use of what is known now as well as what the staff in London knew then.
There is abundant evidence that in 1942, almost immediately after the British withdrawal from the continent, plans for the Allied re‑entry into Europe were commenced. In all, before the final plan of Overlord, there appear records of nine plans. In many of these the passage across the long flat beaches of France was envisioned. And with that, once it was contemplated, there was the ugly predicament of deep-draught ships requiring to be moored for unloading •some three miles offshore. Lighterage on this scale would be slow p39 and, with sea running and ships rolling, subject to long interruption.
The legend persists that in directives to Combined Operations planners, the Prime Minister asked for a solution to bridging this water gap, and called for "piers that would float up and down with the tide," with the helpful addendum, "Don't argue about it. The difficulties will argue themselves."
The earliest responsibilities for dealing with this obviously seafaring problem of the water gap — lightering from ships and unloading across beaches — went via Admiralty into capable and knowing hands, hands that knew the sea and the specialties of beach warfare: Technical Development Division of Combined Operations. Subsequently it was shifted to the British War Office.
Rear Adm. J. Hughes-Hallett, RN (then Commodore), who was in charge of the naval planning for Overlord, acceded to this shift. Combined Operations at this time was in conflict with certain planning divisions of the Admiralty. Further, the prospective British head of the project, one Brig. Bruce White, was close to the Prime Minister. The shift would take the project out of an area of conflict and insure sympathetic attention.
Under Brig. Bruce White, a section of the British War Office known as Transportation 5 (Tn5), which had been working with the military problem of bridging in its more conventional applications, took over. This transportation division was the one concerned with military transport on inland waterways.
Wigtonshire, Scotland, then became the nursery area in which Mulberry prototype structures grew. Col. V. C. , assisted by Major Beckett, assembled a pioneer force of experimenters at Cairnhead. From then on, on the British side, the design, installation and operation of Mulberry was an army project. The Admiralty retained only the towing side of the operation as its responsibility, and was regarded as a consulting authority only on design and mooring.
The first outstanding feature of Mulberry was an outer wall of huge concrete caissons, known as Phoenix units, which, when sunk in a line, would produce a breakwater. In this matter of breakwater units that could be towed to the site and there sunk in place as caissons, there was some precedent. In 1917 Mr. Churchill proposed an artificial harbor in connection with a projected landing behind the German lines in Flanders. Further, both Cherbourg and Dover were "made ports." Concrete caissons composed the breakwaters in part. Use of large caissons was also developed in the famous caissons, the British "forts" for the Thames estuary in World War I.
In the design of the huge concrete caissons for Mulberry, the Phoenix units, the famous English small‑boat sailor and civil engineer Iorys Hughesb played an important role.
Rear Adm. J. Hughes-Hallett, RN, the leading naval planner, augmented this caisson breakwater concept with the idea of a row of sunken blockships known by the code word "Gooseberry."
Lt. Comdr. J. G. Steele, RN, drew up the first plan of a harbor off the Normandy coast.
The conference, "Rattle," held at Largs in Scotland 2‑3 July, 1943, was the first official general review of the Overlord p41 invasion plan for Northwest Europe. It was the product of the planning group known as COSSAC — Chief of Staff, Supreme Allied Commander. Mulberry appeared briefly in the plan but without detail.
Shortly after the Largs "Rattle" conference, the Overlord plan with sketches of two artificial harbors was submitted at Quebec, in July, to the historic Quadrant conference of the Combined Chiefs of Staff, with both Churchill and Roosevelt present.
One harbor, to be known as "Mulberry A," was to be in the American sector of the towns of Vierville and St. Laurent, and the other, "Mulberry B," in the British sector, off Arromanches.
That the curious name of Mulberry3 was chosen as the code word without any special reason seems sad when one recalls the care and delight which went into giving hidden significance to some of the operational names such as "Husky," "Sledge Hammer," "Torch," and "Round Up." A bit of chance information, gleaned under most peaceful circumstances in a Washington garden where there was actually a mulberry tree growing, does a little to repair this obvious oversight. It seems the mulberry tree is known as the fastest growing tree.
A more bloodthirsty name such as "Tiger's Mouth" would have helped Mulberry men no end in later days to get attention and material for the project.c
Whatever its deficiencies as a name under which to negotiate or strike chill fear into the hearts of the enemy, to p42 the handful of officers on Admiral Stark's staff who came across the tantalizing paragraph in the summary of the first Combined Chiefs' document, the Mulberry concept captured the imagination completely as the key operation of the entire proposed operation.
1 Brest fell September 18, 1944.
2 An artificial harbor was also planned for the invasion of Japan, with many modifications.
a The fiasco that was the Dieppe raid was also hatched in the same plans division of Lord Mountbatten's Combined Operations. The official public account of the raid, extending over five whole chapters of a book on commando operations (Combined Operations, chapters 14‑18) written at the behest of the government and published under Mountbatten's auspices in 1943 while the war was still being waged, admits it was a disaster — it was quite impossible to pretend otherwise — but is at pains to spin it as a valuable learning experience. Beyond government circles, consensus was quickly reached that common sense would have taught the Allies that lesson without exacting so horrific a price.
b Hugh Iorys Hughes was Welsh, not English.
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Page updated: 10 Feb 22