New Delhi, May 26 -- D-Day was supposed to happen on June 5, 1944. The story of why it ultimately took place on June 6 is one that has been a bit lost to history, consumed by the larger events surrounding it.

One day might not seem like much in the grand scheme, but it was a seismic delay in plans for the unprecedented and daring invasion, which would deploy nearly 160,000 Allied troops in Normandy. Ultimately it came down to a recommendation from a shrewd Scottish meteorologist, Group Capt. James Stagg, who had to tell everyone, including Gen. Dwight D. Eisenhower and the Allied leadership, something they didn't want to hear: The weather was going to be catastrophically bad. And no, he wasn't certain about it.

The tense 72 hours before...