The greatest day in history was VJ day.
The senseless killing ended, for the time being.
My dad was saved from being fodder for Olympic.
I exist as a direct result of Little Boy and Fat Man, as do countless others both American and Japanese.
Overlord was a necessary piece of the puzzle to be sure but it gets more fame than others equally important.
There would have been no D-Day for example if Eagle Day (Adlertag - 13 August, 1940) had achieved it's objective.
It was a long, long road from September 1939 to August 1945.
Mankind didn't learn much if anything from it, that's the real tragedy.