D-Day. Sixth of June

It was really before my time.  I was only one year old back in June of 1944.   D-Day was the first time the Anglo American forces were strong enough to fight the main German army on the German's home turf.  Previous combat in North Africa and Italy were against small detachments like Rommel's Africa Corps, or bloody but small scale combat against limited German forces, fighting a defensive battle in very defensible Italian terrain. 
   Humongous forces were poured into D-Day.  The operation looked all kinds of dangerous.  Eisenhower, supreme commander, the man with the best view of the situation, found it so dicey that he prepared a press release, to be issued in case the landing was defeated.  Had he needed to use it, the setback  to Anglo American arms would have been staggering.  1942 and 1943, two whole years of war production and training, went into marshaling the D-Day forces.  Had the Germans won, much of this vast investment in infantry, tanks, artillery, warships, and warplanes would have been lost.  It would have taken at least another year, probably two, to build up to launching a second invasion.  Give Hitler another year or two and there is no telling what might have happened.  The Germans might have perfected nuclear weapons.  The V-weapon program would have had another year or two to rain destruction upon London.  Time to bring a radical new U-boat, the type 21, into operation.  Lots of things could have given Hitler victory.
   Anglo American victory was possible by defeating the U-boats in the Atlantic in 1943.  We could not have moved our troops, let alone the vast quantity of supplies needed to support our forces, and keep England fed and producing,  had the U-boats kept sinking ships at the rate they had in 1942.  Second, USAAF and the RAF had pretty much blown the Luftwaffe out of the air by 1944.  This guaranteed that the Germans couldn't sink the D-Day armada in mid channel, or render close air support to advancing Panzer divisions.  Finally, the Germans did not know where the Anglo American invasion would come.  The entire coast of France, including the Riviera, and the low countries, was possible.  The Germans had to spread their troops  up and down the European coastline, whereas the Anglo Americans could concentrate all their forces on the invasion beaches, giving a solid superiority in numbers at the crucial spot. 
   As it was, it was a tough fight.  A lot of bravery, and sacrifice carried the day, just barely.  And, once ashore, the Anglo American armies could beat the German army in a standup fight.