Decision Support June 6, 1944

The forecast for the D-Day invasion of Europe on June 6, 1944 is arguably the most important case of decision support in history. The stakes could not have been higher. Success or failure was utterly dependent on an accurate prediction. Considering the time and place, the forecast would have been challenging even with modern techniques, but it had to be made with the resources available more than 70 years ago. Collaboration between different service elements was essential, as was collaboration between different nations. That collaboration had to be done in total secrecy. Wartime pressures added difficulties that would never occur at other times. Yet in spite of everything the forecast accomplished what it needed to—ensuring the decision to proceed with the invasion was the correct one.

A brief review of the problems encountered in making the D-Day forecast, how they were overcome, and what they teach us about decision support will be presented. There will be a short summary of what happened when modern-day meteorologists were presented with the same information available at the time and asked to make their own prediction for June 6, 1944.