MULBERRY HARBOURS ~
The 'Mulberry Harbours' was a WW2 civil
engineering project of immense size and complexity. The floating harbours were
designed to provide port facilities during the invasion of Normandy in June 1944
until French ports like Cherbourg were captured. How did they erect two
harbours, each the size of Dover, in just a few days in wartime when Dover took
came to ousting the Germans from their entrenched defensive positions along the
'Atlantic Wall,' planners knew that blockading and attack by air would not be
sufficient. The Germans would defend their front lines with great vigour and
only a large scale landing of men, their equipment and supplies would be up to
the task. In the crucial days and weeks following the landing, the Allies could
ill afford delays in supplying their advancing forces. Intelligence reports
indicated that French seaports would be heavily defended by German forces and
they were liable to be disabled in the event of imminent Allied occupation.
Planners also drew on the main lesson learnt from the ill-fated
Dieppe Raid that heavily defended ports could not be taken without crippling
losses. The plans therefore envisaged a need to create secure harbour
facilities away from heavily defended ports and close to the landing beaches.
facilities were needed quickly where none existed. That was clear enough but
conventional construction techniques required detailed ground and seabed survey
information, precise building plans and the assembly of a highly skilled
construction force of thousands; an impossible task under normal circumstances
but particularly so when the time available for the construction phase was
measured in days and the construction sites were within easy range of enemy
aircraft and long range guns!
Normandy was chosen as the location for the 2nd front the decision to design and
construct two artificial harbours in the relative safety of the UK mainland was
agreed, but, it must be said, with misgivings especially on the part of some
high ranking Americans. To address the issue of skill shortages the design was
to allow for the transportation and assembly of the many harbour components by a
competent workforce under the supervision of engineers.
In 1917 Churchill drafted detailed
plans for the capture of two islands, Borkum and Sylt, which lay off the Dutch
and Danish coasts. He envisaged using a number of flat bottomed barges, or
caissons, measuring 37m x 23m x 12m which would form the basis of an artificial
harbour when lowered to the seabed and filled with sand. Events moved on and
Churchill's proposal was filed away and was never published.
In 1941, Hugh Iorys Hughes, a
quiet unassuming Welshman from North Wales had similar ideas. He was a
successful civil engineer living in London when he submitted plans to the War
Office. Their potential value was not recognised until Hughes' brother, a
Commander in the Royal Navy, drew the plan to the attention of more senior
officers. This intervention brought Hughes and his ideas to the fore. It was to
be the beginning of a long association with the Mulberry project.
Other accounts credit Professor J
D Bernal with similar ideas expanded upon by Brigadier Bruce White who later
helped draw up plans for the final design. He was greatly assisted by Allan
Beckett whose "whale" design for the roadway was selected in preference to
Hamilton's Swiss Roll and Hughes' concrete Hippo (more information below). With
a project of this size and complexity it is not possible to say that the idea
was the property of any individual but all of the above were major players in
the story of Mulberry Harbours. Both Bruce White and Allan Beckett wrote papers
about aspects of Mulberry, details of which can be found at the bottom of this
page under Reading Material & Websites.
Early in 1941 a new department
within the War Office was set up code named 'Transportation 5' (Tn5) under Major
General D J McMullen. It had responsibility for port engineering, repairs and
maintenance. The Mulberry project and the need to construct sufficient
embarkation points on the shores of the UK, soon became its top priorities.
Under the command of civil engineer Bruce White their first project was to
construct two military ports in the Clyde estuary one of which was the Gare
There were many meetings with the
Americans about the options to provide sheltered harbours.... sunken ships,
concrete caissons, concrete pontoons, collapsible canvas floating barriers and
Pykrete to name but some. There was scepticism on both sides of the Atlantic
and some believed that Mulberry was even more fanciful an idea than Pykrete! To
overcome the doubters in his own ranks Mountbatten called them to a meeting in
one of the bathrooms of the Queen Mary. They were en route to an important
meeting with the Americans in Quebec where the matter of artificial harbours
would be decided. As they entered the bathroom they saw a partially filled
bath, 40 or so ships made out of newspaper and a Mae West lifebelt.
Half the 'fleet' was placed in the
bath and the most Junior officer present in the crowded bathroom, Lt Commander
Grant, RN, was asked to make waves with the back of a brush. In no time the
vessels sank. The demonstration was repeated this time with the 'fleet' floating
inside the Mae West. To the immortal command "More waves please Lieutenant
Grant" the heavily braided onlookers saw that all the vessels survived.
One USA sceptic, Admiral John
Leslie Hall Jr., US Navy Commander, was scathing of the idea, predicting that
the Mulberries would never stand up to the rigours of the English Channel and,
in any event, he could unload 1000 LSTs at a time on open beaches... more than
enough to supply the advancing Allied forces. His prediction was, at least in
part, later proved to be correct in the case of Mulberry A (details below), but
the balance of opinion was in favour of the project and approval was given to
proceed. The task was given to Mountbatten's Combined Operations. However, he
soon realised that the resources needed were way beyond those of his
Command and he contracted out the operational aspects to the War Department.
Three designs were selected for
further evaluation. The first from the War Office was for flexible steel bridges
on pontoons of steel or concrete with pier-head units on adjustable legs to take
account of the tides. The second from the Admiralty was a flexible floating
construction of timber and canvas held together with steel cables and similar in
appearance to a Swiss Roll in its stored condition. The third from Iorys
Hughes envisaged the use of steel bridges to be mounted on concrete caissons and
floated to the sites and sunk in position. Initially none were to be protected
search was on for 'test' beaches with characteristics similar to those of
Normandy - flat, sandy, remote and sparsely populated to ensure an
effective security cordon. After exhaustive surveys, Wigtown Bay on the
Scottish side of the Solway Firth, with its nearby harbour of Garlieston,
was chosen. The whole area from Garlieston to the Isle of Whithorn (not an
island!) was declared off limits to all except local fishermen. Work
started on the construction of a military camp at Cairnhead to accommodate
the increasing numbers of engineering personnel (Sappers) with an
additional 200 men being accommodated in the village hall in Garlieston.
prototypes were constructed at "the Morfa," Conwy in North Wales where over 1000
local and outside workers were drafted in for the purpose. One such was Olef
Kerensky, the son of a former Russian Prime Minister, who supervised the
construction process. With his mother he fled from Leningrad at the age of 10
and entered the UK on a false passport! Raymond Lee was a small boy when he
witnessed the construction of the massive caissons from his home on the other
side of the Conwy estuary.
The Morfa area was transformed
into a huge construction site Hughes' three 'Hippo' caissons were towed to
the site in Rigg Bay near Garlieston. Two 'Croc' roadways were attached to the
metal bars on the Hippos and various combinations were tested in a variety of
weather and tidal conditions. Fully laden vehicles were driven across the
roadway. The testing proved invaluable since the behaviour of the components
could be analysed and corrective action taken where necessary. It was found that
the floating piers did not rise and fall with the tide as predicted but Hughes
found a solution in the provision of adjustable spans between the Hippos and the
roadway. A more serious problem was the unexpected pitching and yawing of the
Hippos causing the attached Croc roadways to buckle. Hughes proposed the
construction of Hippos of diminishing size on which the roadways would sit.
Hughes' design was not alone in
experiencing problems. When Hamilton's Swiss Roll roadway was tested with a 3
ton tipper truck the roadway sank in under two hours. Adjustments were made but
further tests in the open sea confirmed that the heaviest load that could be
carried was 7 tons - far below what was necessary for the movement of tanks. The
Swiss Roll roadway design was soon abandoned. In the end it was Beckett's
flexible bridging units, supported on pontoons, that produced the best results.
Churchill was not happy with the rate of progress. He had sent a memo to
Mountbatten on the 30th May 1942... "Piers for use on beaches. They must
float up and down with the tide. The anchor problem must be mastered. Let me
have the best solution worked out. Don't argue the matter. The difficulties will
argue for themselves." Progress at first was slow as discussions on competing
ideas by the many interested parties were considered. Churchill penned a number
of increasingly irate messages in the following months culminating in this one
of 10 Mar 1943. "This matter is being much
neglected. Dilatory experiments with varying types and patterns have resulted in
us having nothing. It is now nearly six months
since I urged the construction of several miles of pier." In response some
organisational changes were made to "get a grip" on the project.
There had been tensions between
the War Office and the Admiralty which sometimes resulted in poor co-operation
and bad communications. After earlier allocations of responsibility had failed
to resolve matters the War Office was tasked to design the caissons and oversee
the development of the pier-heads and piers while the Admiralty were tasked to
design and oversee the development of the floating breakwaters. This agreement
was later refined to take account of continued Admiralty concerns about the
berthing and navigation guides and it was therefore agreed that they would be
responsible for the towing all the components across the channel, the layout and
positioning of the harbours and the navigational channels and moorings.
The early designs did not envisage
protective breakwaters but it became clear that an area of calm water would be
required.. In addition to the breakwaters, included in the final plans, other
water calming measures considered included "bubble breaker" and "lilo".... the
former involved pumping high pressure air along perforated pipelines causing a
large volume of compressible air in the sea sufficient to absorb the power of
heavy breakers. The latter were large canvas bags extending some 4m below the
waves and 3m above. They were inflated to low pressure and operated on a similar
basis to the bubble breaker in that they would absorb the power of the waves by
allowing the air they contained to be compressed.
On conclusion of the tests a
final design was decided upon. There would be two harbours each comprising two
breakwaters, offshore and flanking, made from hollow ferro-concrete caissons. To
provide extra protection 70 obsolete merchant and navy vessels (block-ships)
would be sunk to fill gaps in the protection provided by the caissons. Inside
the resultant protective cordons there would be pier-heads connected to the
shore by Beckett's floating steel roadways.
In view of Iorys Hughes' commitment to the
project and expertise he was invited by Churchill to serve the project as a
ideal specification was for a pier a mile long that could withstand gale
force winds and be capable of berthing large coasters. To do this the
artificial harbours would need to provide sheltered conditions and be
larger than the port of Dover which had taken 7 years to build in
peacetime! Within the sheltered areas stable floating quays would be
located some distance from the beaches to provide sufficient water depth
(6.7 meters) for the docking vessels. These quays would be linked to the
beaches by floating roadways to allow the discharged goods and equipment
to be transported ashore in fleets of lorries. Two harbours would be
required - Mulberry A for the USA beaches of Omaha and Utah and Mulberry B
for the British and Canadian beaches of Gold, Juno and Sword. The designs
would allow for the floating caissons to be secured in place in four days.
Each harbour would have a capacity of 7000 tons of vehicles and
supplies per day.
For security reasons randomly
selected codes were used to describe the various components of the two Mulberry
~ Breakwaters ~
Bombardons - floating
breakwaters comprising huge, metal, crucifix shaped structures ballasted and
firmly anchored in place. They were the outermost barrier and therefore the
first line of defence against rough seas.
Phoenexes - 146 concrete
caissons 60 metres long, 18 metres high and 15 metres wide making up 9.5
kilometres of breakwater. They were airtight floating cases open at the bottom
with air-cocks to lower them to the sea-bed in a controlled fashion. Around 2
million tons of steel and concrete were used in their construction.
Gooseberries - 70 obsolete
merchant vessels (block ships) were amassed at Oban on the west coast of
Scotland, stripped down, ballasted and primed with explosive scuttling charges
The vessels sailed under their own steam and were sunk in 5 locations including
the 2 Mulberry harbours.
~ Pierheads ~
~ Roadways ~
Beetles - concrete and
steel floats or pontoons to support the roadways. Each capable of taking the
weight of 56 tons + 25 tons (being the weight of a tank).
Whales - 16 kilometres of
Buffer - approach span
from the floating roadway to beach.
Rhino - power driven
pontoon on which cargo was brought ashore.
The final configuration of all
these units when assembled and positioned can be seen in
this photograph although the Bombardons were too far out to be seen here.
of the operation would depend on accurate and detailed topographical information
about the beaches and coastal towns along the French coast. Aerial photographs
helped identify likely locations but, to obtain more detailed views, the
Government appealed to the public for holiday photographs and postcards of
unspecified coastal areas of France. However much more detailed information on
the target beaches and their approaches was required. Local conditions such as
the composition of the beaches, hidden underwater banks, German defensive
obstacles, depth of water, tidal conditions etc would all be taken into account
in the planning of the project. The stakes were very high - bad intelligence
could jeopardise the whole vast project.... there was no room for error.
Year's eve 1943, under the leadership of 24 year old Major Logan Scott Bowden of
the Royal Engineers, a unit set out in motor torpedo boats to reconnoitre the
area around Luc-sur-Mer. They transferred to a hydrographical survey craft and
moved closer to shore before Major Logan and Sgt Bruce Ogden-Smith swam to the
beaches where they took samples of sand, mud, peat and gravel which they stored
in labelled tubes. They were careful not to leave behind any evidence of their
visit lest the Germans became alerted to their clandestine activities - much of
their lateral movement along the beaches was below the tide mark! Their mission
was a total success.
A month or
so later, this time using a midget submarine for transport (towed part of the
way), the area to the west of Port-en-Bessin and Vierville was visited and a few
weeks later the Omaha beach area. Two scale models of the landing beaches were
prepared using all the information gathered. One was held by the War Department
in room 474 of the Great Metropole Hotel in London and a duplicate in the Prime
Minister's room in the War Cabinet Offices - two of the most secret rooms in the
At Cairnryan, just north of
Stranraer in south west Scotland, the information gathered about the beaches was
used to construct a "life size" reproduction of the beaches. This would allow
the planners to assess the effectiveness of the current landing techniques and
the movement of men and machinery over the terrain.
The Manufacturing Process
of the project was enormous and was in danger of over-stretching the capacity of
the UK's civil engineering industry. From late summer of 1943 onwards three
hundred firms were recruited from around the country employing 40,000 to 45,000
personnel at the peak. Men from trades and backgrounds not associated with the
construction industry were drafted in and given crash courses appropriate to
their work. Their task was to construct 212 caissons ranging from 1672 tons to
6044 tons, 23 pier-heads and 10 miles of floating roadway.
Most of the concrete caissons were
manufactured on the River Thames and the River Clyde in some cases using hastily
constructed dry docks. The steel "Beetle" floats were assembled in Richborough,
Kent, the concrete Beetles at Southsea, Marchward and Southampton and the
pier-heads and buffer ramps at the Morfa site Hughes had used for the
manufacture of his Hippo caissons. Trials continued to be run in the Garlieston
area of the Solway, even during the manufacturing phase, on for example, the
Hughes' involvement continued
throughout the manufacturing period and beyond. He helped identify Selsey and
Dungeness on the south coast of England as ideal places to "park" the completed
caissons until needed. Also closely involved in the planning for D-Day and the
Mulberry Harbours was Sir Harold Werner. He was a rather overbearing, single
minded individual who did not court popularity and consequently his valuable
service in finding solutions to insurmountable problems and generally keeping
the project on schedule, went largely unrecognised after the war.
A large number of British and USA
tugs were requisitioned to tow the Mulberries from their assembly point near
Lee-on-Solent to France. Operation Corncob got underway when the first of the
tugs set off on June 4 later to hold their position in mid channel when D-Day
was delayed by a day. When the invasion finally got underway most caissons were
positioned about 5 miles off the French coast.
Responsibility for Mulberry B off
Aromanches fell to the No 1 Port Construction and Repair Group. They received
orders to sail on June 6 1944 (pm) and by the early hours of June 7, under the
command of Lt Col Mais, markers were in place at high tide level and on higher
ground, for alignment purposes, for the first two piers. Elsewhere further out
to sea marker buoys for the caissons and block ships were positioned under the
command of Lt Col Landsdowne of the RN. This done the block-ships slipped their
moorings in Poole harbour and sailed for France on their final voyages.
Scuttling them in pre-determined 'overlapping' positions was a tricky operation
but essential to ensure effective protection against high seas and fast flowing
Similar operations were in
progress at Mulberry A off Vierville-Saint-Laurent but here the vessels came
under heavy enemy fire. The tugs, which had accompanied the vessels, and which
were to assist in their final positioning, dispersed earlier than planned. By a
stroke of good fortune the 2nd and 3rd block-ships were sunk by the Germans in
roughly the correct positions. In all 5 Gooseberries were positioned to provide
the best protection for the two Mulberry harbours and for other beach landing
points at Utah, Courseulles, 11k east of Arromanche, and Ouistreham. These
breakwaters provided a good measure of protection during and after the
construction of the 2 Mulberry harbours and in the other beach locations. The
UTAH beach was a major logistical supply base for the Americans up to November
'44 thanks to the protection afforded by its 'Goosberry.'
The Bombardons were towed out on
June 6 to their moorings which had been laid previously by boom laying craft.
However a mistaken order resulted in the Bombardons being placed in water some
20m to 24m deep rather than the designed 13m and they were strung out in a
single line when there should have been a double line. The effectiveness of this
outer barrier had been compromised.
On D+1 the caissons, each with a 4
man crew, two sailors and an anti-aircraft gun emplacement, were towed to
positions about a mile off-shore and handed over to a fleet of powerful harbour
tugs which manoeuvred them into their final positions. The caissons' sea valves
were opened until they settled at previously agreed depths. Each Mulberry was
about a mile long and stood about 30 ft (9m) above sea level at low tide and 10
ft (3m) at high tide. The block-ships at Mulberry B were all in position by June
13th and formed two crescent shaped harbours which accommodated 75 Liberty ships
and small craft.
installation of the stores and LST piers proved to be more of a problem.
The tows began to arrive at Mulberry B on D+4 and work continued
throughout the night. Choppy seas made the manoeuvring of the bridging
spans very difficult. By D+8 the stores pier and roadway amounting to 1.2k
was in place and operational. The 2nd stores pier was operational by July
8. It was later discovered that the Beetle floats to support the roadway
had been positioned in an alternate pattern rather than opposite each
other as the design intended. This proved to be a costly error when
consequential stability problems were experienced. The Luftwaffe attacked
Mulberry B on July 15 but such were the defences that 9 of the 12
Messcherschmitts were shot down.
photo opposite (and close-up) were sent in by Scott Blyth who wrote; On June
12, 1944 my father, Lt. John S. Blyth, flew a photo recce mission to the Loire
Bridges. It was sortie 1841 of the 14th Squadron of the 7th Photo Group (USAAF).
The targets were La Huichetiere, Nantes Airfield, Le Port Boulet Bridge damage
assessment and the Loire Bridges from Nantes to Tours. He was based at Mt Farm
near Oxford and on that mission flew Spit MK XI PA 841. Crossing the coast over
Omaha Beach he took at least one photo of the beachhead. It appears to
contain one of the piers of Mulberry A.
Mulberry A was in use for less
than 10 days when, on June 19, it was severely damaged by the worst period of
sustained severe weather for 40 years. Out of 31 caissons laid in position 21
were damaged beyond repair with broken backs and sides. Mulberry A was never
used again and parts of it were scavenged to repair damage to Mulberry B. The
Americans quickly reverted to the traditional methods of unloading from landing
craft and DUKWs directly onto the beaches often coming in on one tide and
leaving on the next. Such was their success that on occasions they exceeded the
impressive performance achieved at Mulberry B.
Each day around 9000 tons were
landed via Mulberry B until the end of August by which time Cherbourg port
became available for use at least in part and, towards the end of the
year, after the capture of
Walcheren, the port of Antwerp. Mulberry B was in
use for 5 months during which time over 2 million men, half a million vehicles
and 4 million tons of supplies passed through the harbour. During this period
several additional caissons where used to reinforce weak points in the
breakwater. [Photos below; HMLST 427 discharging her
cargo onto Mulberry A prior to the storm.]
The Mulberry project was for
certain a great feat of engineering - a highly complex task completed in just 6
months of manufacture, by hundreds of contractors in dozens of locations, under
wartime conditions and a serious shortage of skilled labour. The planners were
heavily influenced by the paramount need to secure the Allied supply line since
the invasion would otherwise stall and collapse as the enemy regrouped and drew
on their reserves. There are those who believe that Mulberry was unnecessary as
exampled by the Americans success in landing supplies directly onto the beaches
after the abandonment of Mulberry A. We'll never know, with any degree of
certainty, what would have happened had Mulberry never been built... and
that for many is all the justification needed for the planners' decision to
authorise the project.
With the exception of those who
were there in the summer of 1944, there is nothing in our collective experience
that allows us to imagine the vastness of the operation and the absolute
necessity to move men, supplies, munitions and equipment to the right place at
the right time. Even the logistics faced by the largest supermarket chains today
pale into insignificance when compared to the task faced by the planners in the
early 1940s. They faced an awesome responsibility and the wider world faced dire
consequences in the event of failure to deliver.
The Supermarket scenario offers an
opportunity to put the scale of the task into a modern context. It has been
calculated that each serviceman needed 6.5lb (3Kg) per day to sustain him in the
field. On this basis1000 men needed around 2.5 tons, 100,000 needed 250 tons and
1,000,000 2,500 tons per day!. As the size of the invading force grew so did the
daily demand for supplies. Then there were the lorries, tanks, artillery pieces,
ammunition, military field hospitals, mobile radar and communications units etc
etc. all of which had to be transported across the channel. Over 4,000 vessels
plied the waters between the UK and Normandy from D-Day and the contribution of
Mulberry B in speeding up the operation and securing the supply chain in adverse
weather conditions, is beyond question. The majority of vessels in use were not
capable of beach landings.
After the war at the Nurembeurg
trials, Albert Speer gave the enemy perspective on the Mulberry Harbours and
their Atlantic Wall defences. 'To construct our defences we had in two years
used some 13 million cubic meters of concrete and 1.5 million tons of steel. A
fortnight after the landings by the enemy, this costly effort was brought to
nothing because of an idea of simple genius. As we know now, the invasion forces
brought their own harbours, and built, at Arromanches and Omaha, on
unprotected coast, the necessary landing ramps."
[Photos. Top looking east towards Arromanche
courtesy of Nigel Stewart and bottom a stranded caisson in Portland
Harbour still dominating the skyline after 70 years (2013).]
Location - Conwy, North Wales. Follow signs for the marina. The plaque
is situated in the council car park next to Conwy Marina. Other Info
- read the full story about the design, testing, development and
manufacture of the
Mulberry Harbours and of the key
role of a local boy cum civil engineer.