The numbers are staggering to think about still today. The sea lane in the Channel that was cleared of mines for day 1 was only 15 miles wide. The places where mines hadn't been cleared turned out real bad for Allied forces.
Here's an interesting piece of work: German Field Marshall report on the D-Day invasion on 20 June 1944. It's amazing how accurate it is, and it concludes that he's putting it in writing, his recommendations for his own purposes.
http://www.history.navy.mil/faqs/faq109-5.htm
(this guy Rundstedt, had been promoted and sacked by Hitler multiple times - by the time he was in command of the Normandy region - the first major incident when he wanted to actually halt the invasion on the eastern front because supply lines were thin and winter was coming. The Wehrmacht (under his command) with SS support divisions (Not under his command - but equally stretched out) had taken all of Ukraine into Crimea and secured what is now Sevastopol naval base all the way north to Moscow. Hitler wanted more and ordered him to advance. He objected but followed orders and continued to advance until the Russians finally stopped them and began pushing back at a place called Rostov. Almost the exact same thing that had happened to Napoleon about a century earlier.
Hitler sacked Rundstedt, for the first time. He would get promoted again, and then sacked again later after Normandy.
The most amazing thing about World War 2, is that had the Nazi war machine had an effective chain of command, and a leadership that was not criminally insane, there was no military force that would have come close to defeating them globally. The german weaponry and technology was so far advanced over anything anyone else had, that's hard to describe.
I read RIo's post and it hits you in the guts.
I can only imagine what it must have been like for an American soldier to hear and actually have to face an MG-42 machine gun for the first time, or for any single one of the pilots in the air battle, to see an ME-262 buzz them at twice their max speed, with no propellers.
Anyhoo - an historical day, in history.