Mulberry Harbour

Mulberry Harbour

"If you have faith the size of a mustard seed, you could say to this mulberry tree, 'Be uprooted and planted in the sea,' and it would obey you!” (Luke 17:6)

Mulberry Harbour was perhaps the single greatest innovation that ensured victory for the Allies in the Battle of Normandy that followed D-Day. Without port facilities, the Allies would never have been able to build up their forces in France sufficiently to be able to withstand the German’s efforts to defeat them.

Allied planners realised at an early stage that they would need a port facility very soon after arriving in France. Without one, all the men and materiel that would be needed to secure the beachhead, would have to be landed directly onto the captured beaches. This would necessitate using landing craft, which were relatively small and inefficient next to the facilities that a deep water port can offer.

However, a port would be hard to capture quickly, and there would be no guarantee that the German forces would not destroy the port before they abandoned it (indeed, most of the ports they abandoned were thoroughly wrecked by the time the Allies reached them).

The solution, in the eyes of Winston Churchill and several senior planners, was to take a port with them. A floating harbour that could be transported directly to France, and assembled off the beaches would ensure that sufficient facilities were in place to land large quantities of heavy equipment to supply the British, Canadian and American armies.

The plan called for two Mulberry harbours to be constructed at Normandy; Mulberry A at the American beach of Omaha and Mulberry B at Arromanches on the British Gold beach. With the beaches successfully captured, elements of Mulberry were towed to France as early as 6 June. Assembly began immeadiately and both harbours were operational within ten days, although amendments and expansions continued well into July.

Unfortunately a large storm struck the beaches on 18th and 19th of June. Mulberry A was almost totally destroyed and Mulberry B was not much better. The decision was made to abandon the American harbour and all the surviving elements were incorporated into Mulberry B. It was succesully reopened and renamed Port Winston. By October when it was officially closed, over 39,000 vehicles and 220,000 men were landed at the port.


The Construction

Facilities all along the south coast were used to construct the various elements. London docks and some ports around the coast were used for building large elements of the harbours, but it was the Solent that sat at the centre of the construction.

A view along Stokes Bay, Gosport, showing a few of the 14 concrete caissons for the Mulberry Habours constructed at the site between 1943 and 1944. The caisson second from the camera has collapsed in its frame during launch. © IWM (H 35554)At Southampton Docks, Phoenix Caissons, the large concrete blocks that could be floated to Normandy and then sunk to create a breakwater, were built in the dry docks of the old port. Photos discovered in Southampton City Archive also showed bombardons, large floating breakwaters, also being constructed ion the King George V dry dock. Records in the National Archives showed that these were tested in Portland Harbour when complete, and they were despatched from there to France in the days following D-Day.

Across the water at Marchwood, a new military port was built largely to serve the forces for the invasion, and to construct pier elements. ‘Whale’ roadways were built here; these had been extremely well designed so that they would be able to flex with the currents that they would be exposed to. These roadways would float above the water on ‘Beetles’, hollow concrete floats that could be anchored to the sea bed. When put together, these floating roadways could stretch one mile out to sea, into deeper water where larger ships could berth at the pier heads.

Further round the coast, Beetles were also built on the River Beaulieu. An old Oyster Bed at Cobb Creek was dredged and became a Beetle construction site.

The largest Solent construction sites were at Lepe and Stokes Bay. Here they built Phoenix Caissons on the beach so that they could be directly launched into the sea. Six were built at Lepe and fourteen at Stokes Bay. All were built concurrently in separate spaces along the beach.



Some legacy of this construction survives in the Solent today. In the 1950s, when the marshland at Dibden Bay was reclaimed, several dozen Beetles were used to create breakwaters behind which the land could be filled. Lines of these beetles still survive on the foreshore today, and at low tide thety can be seen from the Red funnel ferries or from Town Quay, lined up along the beach across Southampton Water. It’s doubtful that these Beetles ever went to Normandy; most likely they were spares from Beaulieu or Marchwood that had been kept in reserve in Southampton Water.

A piece of Whale roadway at the Red Funnel terminal in Southampton.During the latter stages of the war, when other ports had been captured and Mulberry was no longer required, large numbers of Whale roadway sections were reused to repair bridges in France. A great many pieces of Whale roadway are still to be found on some of France’s quieter roads even today. In Southampton, two sections were used by Red Funnel as boarding ramps for their old ferries. One section is still there today. Although it is no longer used as a boarding ramp for the newer ferries, it remains in impressive (if untidy) condition. Mulberry was only expected to last six months as a port; the fact that elements such as these survive in such good condition shows the true quality of their construction.

In Langstone Harbour lie the remains of a large Phoenix Caisson that was abandoned here in 1944. This caisson developed a crack during construction and would not have survived the journey to France. Instead, it was towed to its present location and abandoned. Research at Hampshire Record Office in Winchester showed that in 1960, the caisson was sold by the Admiralty. Initially it was due to be sold to SB Lunzer & Co Ltd., a London based company and removed. However this prompted protests from local residents and the Admiralty, no doubt somewhat surprised by this response changed the sale conditions. Instead of requiring the caisson to be removed, they now stipulated that it must remain undisturbed. This wasn’t exactly a good deal for Lunzer (who it is believed, were originally interested in the scrap value of the reinforcing steel), and if their history was often blighted by such poor value purchases, it may help explain their subsequent liquidation. The caisson lies on land held under lease by Langstone Harbour Board and in the absence of any other owner, it is most probably considered to be their property today.

Two more phoenix caissons survive not far away in Portland Harbour. In 1946, ten Mulberry Harbour Phoenix Caissons, reputedly used at Normandy, were taken to Portland. They were used as a breakwater and to provide shelter for the construction of the new Castletown Pier (now Queens Pier) and it was originally intended that all ten would be retained permanently, to create an inner harbour that could be used for berthing large Royal Navy destroyers.

The two Phoenix caissons in Portland Harbour, probably the best preserved examples of Mulberry Harbour left in existence.However, in May 1953 the British Admiralty placed the Phoenix Caissons at the disposal of the Dutch government for use in dyke repairs in the wake of a massive storm in February of that year. Shortly thereafter, eight were re-floated and towed to Zeeland province. By July, six were in Zeeland, and two more were ready to be towed over. One of the first six caissons is believed to have run aground and was later used at Serooskerke. Four were used to block a dyke on the 6th and 7th November 1953 at Ouwerkerk. One was used at Kruiningen on the Scheldt estuary and another two at Dreischor (Stevensluis). The four caissons at Ouwerkerk were designated protected monuments in 1965 (although this may have been 2003 ). In 2001 they were officially opened as a museum dedicated to the 1953 floods.

The two caissons that were left in Portland today provide shelter for ships moored on the west side of Queen’s Pier. They were designated as listed buildings in 1997.


Interactive Map

Support the Maritime Archaeology Trust Donate to save Bouldnor Cliff Sign up for our newsletter Become a friend - Join today