On 6 June 1944 Allied armies stormed ashore on the beaches of Normandy to open the campaign that would for the Allies be the defining phase of the Second World War. Months of careful preparation and planning came to fruition during the crucial early hours of D-Day to ensure overall success and, despite some reverses, by the end of the first day over 150,000 Allied troops were firmly established in Normandy.1 Behind the soldiers, as they waded and fought their way on to mainland Europe, lay the vast armada assembled by the Allied nations, consisting of 1,213 naval fighting ships supported by over 5,500 landing, ancillary and merchant vessels. Within 24 hours 6,000 vehicles and 10,000 tons of stores had been put ashore.2 Overhead the sky was filled with aircraft of the RAF and USAAF, who dominated the western theatre of operations to such an extent that they had achieved not just air superiority, but total air supremacy. On D-Day the Allies could call upon in excess of 12,000 aircraft, while the Luftwaffe in northwest Europe could muster fewer than 200 serviceable aeroplanes to contest the landings.3