The first thing to remember about D-Day is that it is something of a misnomer. It was not one day, although I am sure it was a memorable day for those who landed on the beaches of Normandy and for the families of those whose loved ones were lost on June 6, 1944. In fact, months and months of preparation had gone into the planning for what was the largest amphibious operation in the history of the world. During one planning session, when discussing the timing of the landing, given the need to take account of both the weather and the tides, Churchill famously asked "When did William cross?" (Of course, William was going in the other direction and with a fairly different level of technological prowess.) Churchill and his aides had also been thinking about the needs of the invasion ever since the deliverance at Dunkirk. They devised all manner of new devices for the invasion, from the "bobbin," a tank improvised to lay down a sheet of sturdy fabric over the soft sands, to the Mulberries, artificial harbors constructed of concrete, floated across the Channel, and sunk in a row to create a breakwater and port to land more supplies and troops. The Allies also created a fictitious First Army Group in Kent, stationed prominently opposite the Pas de Calais to convince the Germans the main assault would come there and not Normandy. And while we think of Normandy as a landing on the beaches, the Allied air forces flew more than 14,600 sorties on June 6. Within 48 hours, about a quarter of a million troops had been landed. Casualties were fewer than anticipated. And, most importantly, the liberation of the Continent had begun. War is an ugly, ugly thing, but this one military operation may have been among the most necessary in the history of Europe. We owe the men who fought, and the men and women who planned, a great debt of gratitude.