The target date meant the AEF would go on the first suitable day after June 1. A number of requirements went into the selection of D-Day, the chief of which concerned tides and moon conditions. The admirals wanted to cross the Channel in daylight to avoid confusion, to control the thousands of craft involved, and to maximize the effectiveness of the fire support. The air force generals wanted daylight before the first waves went ashore in order to maximize the effectiveness of their bombing runs. Both had to give way to the army generals’ insistence on crossing at night, in order to preserve surprise up to the last minute, and landing right after first light, in order to have a full day to get established.
Rommel anticipated that the attack would come at high tide, as that would give the first waves the shortest open beach to cross, but that only showed how little he knew about amphibious operations. From the beginning, the AEF was determined to land on a rising tide so that the landing craft could run right onto the beach, then float free on the rise.
The AEF needed at least a half-moon the night of the crossing, enough to provide some illumination for the fleet and for the paratroopers, who would be dropping into France some five hours before H-Hour.
A rising tide at first light following a night with a suitable moon occurred during two periods in June, the 5th, 6th and 7th and again on the 19th and 20th. Eisenhower picked June 5 for D-Day.
The southeast coast of the Cotentin and the Calvados coast of lower Normandy would be the place. June 5 would be the date. H-Hour would be dawn.
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Rommel had no inkling that the AEF suffered from a shortage of landing craft. He thought just the opposite. Further, the Double Cross spies were feeding him false information. His guess as to the date, therefore, was badly off. In April, he thought it would come in the first or third week of May. On May 6, he wrote his wife, Lucie, “I’m looking forward with the utmost confidence to the battle—it may be on May 15, it may not be until the end of the month.”22 On May 15, he wrote Lucie, “Mid-May already. And still nothing doing. . . . I think it’s going to be a few more weeks yet.”23 On June 1, he consulted moon and tide tables and declared there were no good invasion tides (high tide at dawn, in his view) until after June 20. The next day he wrote Lucie, “There is still no sign that the invasion is imminent.”24
Hitler was no better. He indulged himself in the hope that there never would be an invasion. On April 6 he declared, “I can’t help feeling that the whole thing’s a shameless charade.” More realistically, he went on to complain, “We’ve no real way of finding out what they’re really up to over there.”25
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“We cannot afford to fail,” Eisenhower had said. The AEF acted on that basis. There was no contingency planning. In a general ground offensive mounted in a specific area over a broad front, World War II attackers had some flexibility in their plans. If the initial assault did not force a breakthrough, follow-up units could be diverted to the flanks or held back to try again another day at another place. Overlord, however, was all or nothing. Hitler and Rommel were absolutely right in assuming that if the Wehrmacht could deny the AEF a foothold, the Allies would not be able to mount another offensive in 1944.
The size of the gamble on Overlord concentrated the minds of the men at SHAEF wonderfully, but it also increased the work load and raised tension to nearly unbearable levels. “If I could give you an exact diary account of the past week,” Eisenhower wrote Mamie in late January, “you’d get some idea of what a flea on a hot griddle really does!” Toward the end of May, he wrote, “I seem to live on a network of high tension wires.”26
I. Distances are given in two ways, by meter and kilometer and by yards and miles, as is done in, respectively, France and Britain. For England, I use miles; for France, kilometers. But of course when the Allies in France talked about distances, they used yards and miles. This inevitably causes some confusion. To make comparison, a simple method is to remember that a meter is only slightly longer than a yard and may be thought of as equivalent; a kilometer is six-tenths of a mile, so just multiply by six-tenths to go from kilometers to miles (eighty kilometers are forty-eight miles; 100 kilometers are sixty miles, and so forth).