Given that WWII started September 1939 and that Germany declared war against the United Stated in December 1941, I wonder if anyone could explain to me why the Normandy Invasion took place in June 1944, so long after the previous critical dates. I understand that the Allies were engaged in Africa and the push north in Italy. However, given the industrial might of the United States and that supplies and material were convoyed to England early on the in the war, I wonder if the Normandy Invasion could have taken place much earlier. What prevented this? I guess I could understand Stalin's frustration with the Western Allies up to 1944? Any thoughts?