When and where was D-Day? As we approach the 75th anniversary of the Normandy landings we will be asked to focus on a specific day, in a specific location, with a limited group of participants: June 6th, 1945; the beaches, and the military personnel who fought for them. With few veterans of the battles still alive it is appropriate to remember and honor those who bravery made the landings a success, at great human cost, and participated in the liberation of Western Europe. The moment is also a good time to reflect on how we compartmentalize war in to distinct times and places. Remembering D-Day helps us see war as a process with broad historical and geographic spans: The Mulberry Harbours served as a bridge across these spans, as I describe in my book, Geopolitical Constructs: The Mulberry Harbours, World War Two, and the Making of the Militarized Transatlantic.
The Mulberry Harbours were an important engineering feat of the Normandy landings that helps us recognizes the achievement of those who hit the beaches on D-Day. The Harbours also expand the where and when of what are usually portrayed as battles limited in time and space. Two Mulberry Harbours were constructed to support the twin set of beaches for the US- and British-led strikes. They consisted of an outer breakwater of scuttled ships, an inner breakwater of concrete caissons towed across the English Channel and sunk in place, and sophisticated floating piers and anchors. Each Mulberry was about the size of Dover Harbour, 8km2.
The Mulberry Harbours have not been prominent in histories of D-Day because the amount of materiel they helped move from the English Channel to the European continent was not as significant as once planned. But just concentrating on the tonnage of weapons and supplies that the Harbours transited misses the bigger point. The invention and deployment of the Mulberry Harbours gave Winston Churchill the confidence to support the Normandy landings. To understand why this confidence booster was necessary we need to see D-Day within the long-term trajectory of British strategy.
The historic scope of the Mulberry Harbours can be said to begin in another war on another shore: the allied landings at Gallipoli in World War One. Winston Churchill was First Lord of the Admiralty when he argued for the Gallipoli landings, and their failure weighed heavily on him as he faced pressure from Roosevelt and Stalin to initiate the western front. Though Churchill was not shy in demanding military actions that would cost many lives, Gallipoli had made him aware of the necessity of logistics to press home the invasion or face stalemate and retreat. The Mulberries were seen as the engineering feat to enable the push on from the invasion beaches, with an understanding that ports on the French coast would be hard to liberate, and sabotaged by the retreating Germans.
The invention of the Mulberry Harbours helped convince Churchill of the likelihood of success. Apparently, a demonstration using a loofah while he was in the bathtub on the Queen Mary en route to the Quebec conference with Roosevelt and his military staff swayed his opinion on the viability of the idea. He demanded invention and action in a pithy memo: "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."
Behind the construction of the Mulberry Harbours was a fundamental shift in Britain's strategy. For over a hundred years Britain had wanted to avoid getting bogged down in a war on the European continent. The killing fields of the western front in World War One had been a tragic failure of this policy and, in the words of US Secretary of War Henry Stimson, "the shadows of Passchendaele" still tainted British policy making. There is certainly a lot of truth to Stimson's observation. However, the British also had a sense that US policy makers were too gung-ho about a contested landing on the French coast. The Mulberry Harbours were one important part of the logistic puzzle that faded the shadows of Passchendaele enough to allow consensus amongst the allies to go ahead with the invasion.
The legacy of D-Day has not ended. One obvious sign is the act of remembrance itself, and what it is meant to represent about symbols such as "freedom," "democracy," and "the West." The geopolitical power behind these symbols is the continued ability of the United States to project itself across the Atlantic Ocean through a military presence in Western, and now Central and Eastern, Europe. The D-Day landings, planned as a sincere goal of liberation from fascism, were the starting point of the construction of the contemporary militarized trans-Atlantic. The projection of US power was evident in Operation Bolero, the transfer of US troops and equipment across the Atlantic which turned Britain in to a huge parking lot for American military might. As war-time resident of Bristol Doreen Govan recalled, public resentment toward the presence of US troops seemed "rather ungrateful really since the reasons they were 'over here' was ostensibly to help us win the war."
The word "ostensibly" reveals a sense that the US presence had wider implications than the liberation of Europe from Nazi rule. As one war ended, another one started. The US forces that had traveled across the Atlantic and fought their way on to the Normandy beaches met the Soviet troops that had battled across Eastern and Central Europe. The euphoria of comradeship and victory was short-lived. The Cold War animosity meant that the US military presence that began with Operation Bolero and moved across the English Channel through the Mulberry Harbours remained in place. The Atlantic region was militarized and remains so to this day.
In 1949 the New York Times reported on State Department plans that would create Western Europe as a region under within the US sphere of influence:
Remembering D-Day is an opportunity for us to remember that wars are not compartmentalized into distinct battles. War is part of a process of geopolitics that involves the projection of power and constructing spheres of influence. To understand war and geopolitics in this way requires us to bridge events in different parts of the world and different periods of history. The Mulberry Harbours were a bridge in two ways. Geographically they spanned the Atlantic to allow the projection of US military power. Historically they spanned a transition from a nineteenth-century British geopolitics to a twentieth-century US geopolitics: Both aimed to create a "balance of power" in Europe.
 Colin Flint, Geopolitical Constructs: The Mulberry Harbours, World War Two, and the Making of the Militarized Transatlantic (Lanham, MD: Rowman and Littlefield, 2016).
 Quoted in Andrew Roberts, Masters and Commanders: How Four Titans Won the War in the West (London and New York: Harper Perennial 2009), p. 394.
 Quoted in Henry Buckton, Friendly Invasion: Memories of Operation Bolero, 1942-1945 (Chichester, West Sussex: Phillimore & Co., Ltd., 2006), p. 4.
 Hanson W. Baldwin, "The Effects of Russia's Bomb on Our Military Strategy: Defense of Western Europe and Implementing of North Atlantic Pact Now Assume Greater Importance, New York Times September 25, 1949, E5.