The Road to D-Day: What Made Operation Overlord Possible

Strategic bombing, Atlantic warfare, and elaborate deception set the stage for the most ambitious invasion in history

This Friday, we’re releasing a post on D-Day—the massive Allied invasion of Nazi-occupied France, also known as Operation Overlord.

When we discussed it a few weeks ago, we were struck by the sheer scale of the operation, for me, like everything else, dealing with World War II. But that conversation quickly turned to an even deeper question: What made D-Day possible in the first place? Long before the landings at Normandy, the Allies had to overcome tremendous obstacles across the air, sea, and intelligence fronts.

They launched relentless day-and-night bombing campaigns to cripple Germany’s ability to fight. They battled across the Atlantic to stop the deadly U-boat attacks that threatened to cut off supplies and troops. They also conducted elaborate deception operations to mislead the Germans about when and where the real invasion would come. At the same time, the Soviet Union was bearing the brunt of the fighting and the losses on the Eastern Front. Stalin was pressing the Western Allies to open a second front in Europe to relieve the immense pressure on Soviet forces. As the Red Army mounted massive offensives, Germany was forced to divert troops, tanks, and aircraft eastward, further stretching its ability to defend Western Europe.

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At that point in our discussion, we decided to write this post as a prequel to our D-Day post. Here’s a closer look at three crucial efforts that set the stage for June 6, 1944: