Closing the Ring by Winston S. Churchill

similar structures which I thought might in the First World War have been used to create artificial harbours in the Heligoland Bight. 3 Now they were to form a principal part of the great plan.
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    This was the scheme of the “Mulberry” harbour, but even so it was not enough. There would not be room for all the ships we needed. Many would have to discharge outside. To shield these and the very numerous naval vessels engaged, an additional scheme of floating breakwaters was proposed. For this purpose several devices were being considered, among them one to create a barrier to wave action by means of a continuous screen of air bubbles discharged from pipes laid on the sea-bed. It was hoped this screen would break up andabsorb the rhythm of the waves. Another device known as a “Lilo” consisted of partially inflated air bags carrying submerged curtains of concrete. These would be moored in line to seaward of the “Phoenix” and enclose a considerable additional area of water. Neither of these ideas reached fruition, but eventually a device called the “Bombardon” was adopted, embodying some of the features of the “Lilo.” It was a cruciform steel structure about two hundred feet long and twenty-five feet high, with all but the top arm of the cross submerged. In the event this device was of doubtful value, as we shall see in due course.
    I was very well satisfied with the prospect of having the whole of this story presented to President Roosevelt with my full support. At least it would convince the American authorities that we were not insincere about “Overlord” and had not grudged thought or time in preparation. I arranged to assemble in Quebec the best experts in such matters from London and Washington. Together they could pool resources and find the best answers to the many technical problems.
    I was now convinced of the enormous advantages of attacking the Havre-Cherbourg sector, provided these unexpected harbours could be brought into being from the first and thus render possible the landing and sustained advance of armies of a million rising to two million men, with all their immense modern equipment and impedimenta. This would mean being able to unload at least twelve thousand tons a day.
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    There was another associated problem on which my mind dwelt, namely, the maintenance of fighting air superiority over the battle area. If we could create a floating airfield, we could refuel our fighter aircraft within striking distance of the landing-points, and thus multiply our air-power on the spot at the decisive moment. Among the numerous devices discussed during this busy voyage was one called “Habakkuk.” This project was conceived by a Mr. Pyke on Mountbatten’s Staff. His idea was to form a structure of ice, large enough to serveas a runway for aircraft. It would be of ship-like construction, displacing a million tons, self-propelled at slow speed, with its own anti-aircraft defence, with workshops and repair facilities, and with a surprisingly small refrigerating plant for preserving its own existence. It had been found that by adding a proportion of wood pulp in various forms to ordinary sea ice the mixture lost the brittle qualities associated with ice and became extremely tough. This substance, called “Pykrete,” after its inventor, seemed to offer great possibilities not only for our needs in Northwest Europe, but also elsewhere. It was found that as the ice melted the fibrous content quickly formed a furry outer surface which acted as an insulator and greatly retarded the melting process. Much development work was eventually done on this side, particularly in Canada, but for various reasons it never had any success.
    I set forth my ideas about this in a minute to the Chiefs of Staff.
    Prime Minister to General Ismay, for C.O.S. Committee
    9 Aug. 43
    Few technical devices or constructions could exercise more important strategic effects than those which