D-day probably wouldn't have been possible if it weren't for the huge Red Army offensive on the eastern front. This article details the scale and significance of the Soviet attack, which is not being recalled and celebrated as much as D-day. Quote:

"It does not disparage the brave men who died in the North African desert or the cold forests around Bastogne to recall that 70% of the Wehrmacht is buried not in French fields but on the Russian steppes. In the struggle against Nazism, approximately 40 "Ivans" died for every "Private Ryan". Scholars now believe that as many as 27 million Soviet soldiers and citizens perished in the second world war."