Ike Selects D-Day
by Joseph Balkoski
Posted June 2, 2014
For four months Eisenhower had focused his undivided attention on OVERLORD, but as of May 8, 1944, he had yet to issue the fundamental order that every Allied serviceman in Britain needed to know: When would the invasion take place? “No single question had been discussed more often,” noted a U.S. Navy OVERLORD study, but at a May 8 SHAEF meeting, Ike resolved to answer that question once and for all. Since January, when Roosevelt, Churchill, and the Combined Chiefs of Staff had agreed, at Montgomery’s insistence, to delay OVERLORD by a month, SHAEF had designated June 1, 1944, as “Y-Day,” code-named HALCYON; as of that date, Ike ordered, all air, land, and naval forces must be ready to execute their OVERLORD mission. However, before Eisenhower selected the invasion date and time, designated in OVERLORD orders as “D-Day” and “H-Hour,” he needed to hear his subordinates’ opinions on how Normandy’s tides—among the most spectacular in the world—and lunar conditions would influence their plans.
Ike’s airmen professed a straightforward requirement: given the hazards of flying thousands of aircraft along highly constricted flight paths in darkness, a full moon would help prevent midair collisions and ease nighttime navigation. The first full moon after Y-Day would occur on June 6 at precisely 6:58 P.M.; the near-full moon on June 5 or 7, the airmen declared, would also do. An invasion date before June 5 or after June 7, however, would make nocturnal flying much more challenging. Ike’s seamen, too, averred that OVERLORD’s convoys must make the perilous English Channel crossing at night to minimize the threat of German air attack. Many ground soldiers took that argument one step further by favoring a seaborne invasion in darkness, but SHAEF’s air and naval staffs vetoed that idea: the preinvasion air and naval bombardment would require at least minimal sunlight to neutralize the enemy’s many formidable coastal strongpoints, as bombers and warships could not hit with precision what they could not see. Finally, all of Ike’s senior commanders concurred that the seaborne assault must begin as early in the day as possible, maximizing the number of troops poured ashore by sunset in anticipation of the German counterattacks that would surely materialize within twenty-four hours of D-Day. That requirement, however, would severely curtail the window of time bombers and warships would have to saturate the beaches with bombs and shells before first-wave troops surged ashore.Continue Reading