The alternate history of June 6, 1944 is too terrible to contemplate
There is an old preacher story, so old it is a cliche of bad sermons now, that goes like this: An angel awoke who had slept through the first two centuries after Jesus had gone down to earth and ascended back to heaven. The angel went to the Lord and asked, “Where did you go?”
Jesus replied, “I've been down on earth.”
The angel asked, "How did it go?"
Jesus said, "They crucified me."
The angel protested, "You must have had a wide influence."
Jesus said, "I had twelve followers, and one betrayed me to my death."
The angel asked, "What will become of your work?"
Jesus said, "I left it in the hands of my friends."
"And if they fail?" asked the angel.
Jesus said, "I have no other plans."
That punchline, I think, is why D-Day remains so compelling. The specter of defeat on June 6, 1944 was overwhelmingly dreadful. The Allies had no other plans. There was no Plan B in case the landings were repulsed.
There are many "pivot" days in human history, when the course of human events swung in a new direction because of discrete actions. It is hard to find another moment in all history when so much rested on an outcome of one day as rested on the success of the Allies' landings on Normandy.
The Soviets, pushing toward Nazi Germany from the east in 1944, had clamored for years for America and Britain to open a second front against Germany from the west. A second front would compel Germany to draw soldiers and materiel away from the Russian front. Allied claims that operations in North Africa, southern Europe and indeed, the UK-US bombing campaign constituted a second front were scorned by Stalin.
Placating Stalin was one reason the Allies had to invade Germany through France. All the military and political leaders remembered early 1918, when the newly-in-power Soviet government under Lenin had made a separate peace with Imperial Germany. Even though all the Allies had agreed early in WW II that no separate peace agreements would be made, the nag was always there.
Moreover, neither Roosevelt nor Churchill had any desire at all to see all Germany overrun from the east and fall under the hammer and sickle. The only way to prevent that was to place American and British soldiers on the ground inside Germany.
Invasion through northern Europe was the only way to do that (Churchill's claim that an invasion from the south, through Europe's "soft underbelly," proved fantastical in rolling up the Italian peninsula. Whatever Europe's underbelly was, it wasn't soft.)
The Allies could afford to succeed by a mere whisker on the Normandy beaches. Indeed, the planned American and British timetable for operations commencing June 7 proved wildly optimistic. But they did succeed, rather handily most places, as it turned out, and that was enough.
But any failure would have been only catastrophic. As in all major military operations, logistics was the central issue. The moon and tide conditions were acceptable on days in May, June and July; in fact, May 19 was seriously discussed as the invasion date for some time. But the Allies' supreme commander, Gen. Dwight D. Eisenhower, postponed the invasion to June 5 because doing so would yield him an additional 100 landing craft, mostly LSTs, used to land tracked and wheeled vehicles directly onto the beach. (Bad weather caused the invasion to be postponed again until June 6.)
A little-known fact is that America was continually shuttling landing craft, both for vehicles and personnel, back and forth from Europe to the Pacific. The availability of landing craft was almost always the key point in setting landing dates for both areas.
A German victory at Normandy would probably have destroyed stocks of American landing craft by two or three years production, maybe more. Not only could there not possibly been another landing even attempted in Europe for a very long time, Pacific operations would have been dramatically slowed. America was set to take the Philippines back from the Japanese beginning in October 1944. The invasions of Iwo Jima and Okinawa, both in the first half of 1945, were to follow. Significant loss of landing craft at Normandy would have thrown that timetable badly off.
Allied failure on the French coast would have meant enormous American and British casualties. Both the 82d and 101st Airborne Divisions would have been entirely destroyed because they could not have been relieved, having dropped inland. All their soldiers would have been killed or captured. The loss of life that defeat on the beaches would have entailed would have degraded the Allies' capability to try again soon almost as much as the loss of landing craft.
The Soviets certainly would not have slacked their offensives had Normandy failed. If anything, they would have pressed all the harder, but would have pressed equally hard for a much larger share of American war production, insisting that they were making better use of it than we were. As they would have been the only dog in the fight, the demands would have been hard for Roosevelt to resist. Not only would all Germany have become communist, so would France, whose communist cells were very active and which would have benefited greatly from having the Soviet army literally next door. Imagine the Iron Curtain falling at the English Channel. The Soviet bear would have easily swallowed countries like Denmark, The Netherlands and Belgium. Likewise, Greece's postwar communist insurgency would have succeeded. Italy might easily have turned communist also.
(Alternatively, the Nazis might well have shifted hundreds of thousands of soldiers from France to the eastern front. If so, they almost certainly would have shredded Soviet formations because, battalion for battalion, the German army was greatly superior and better led. The Soviets would still have won out, but it would have taken longer and at much greater cost all around.)
European Jews, of course, would have been wiped out since the "final solution" would have proceeded apace. Israel would not exist today. The Soviet Union might have become dominant in the Middle East and there's no point in even trying to speculate on what the next decades would have held for the Arabs (or Persians, since the Russians had long cast a covetous eye on Iran's year-round warm-water ports).
Roosevelt, of course, would not have been reelected that fall. He certainly would have sacked Eisenhower and Eisenhower's boss, Army Chief of Staff George C. Marshall. (Eisenhower actually would certainly have tendered his resignation. Marshall had survived the post-Pearl Harbor headrolling, but could not have survived failure at Normandy.) There's no point speculating what Republican President Thomas E. Dewey would have done with the office, but it is fair to say he would not have pushed for the creation of the United Nations, which was mainly Roosevelt's brainchild (for good or ill, take your pick), nor would there have been any reason for Stalin to cooperate with its formation, anyway.
Britain's people were incredibly war weary by mid-1944. Success in Normandy emboldened them to see the war to its bitter, bloody end. They remembered all too well the defeat of Dunkirk, when the British army had been evacuated from the French coast at the war's beginning, leaving behind its dead, almost all its vehicles and most of its weapons. Failure at Normandy would have caused Prime Minister Churchill's unemployment faster than Roosevelt's.
I have little doubt that some form of British peace party would have gained the Parliamentary majority and the PM's office. Might the Brits have sued Hitler for a separate peace? Maybe. Already strongly tended toward socialism, it's not hard reasonably to imagine that the UK itself would have turned communist by the 1950s had the Soviets dominated all western Europe.
Without Britain (and I'm treading very speculative ground here, I admit), America could not have continued to oppose Hitler, nor have offered any resistance to Soviet dominion of practically all Europe after they had cleaned up the Nazis. We would have continued to make war against Japan, of course. But consider that with sea-land operations slowed greatly by loss of materiel at Normandy, Japan would probably have been bombed into true oblivion; the Pacific War's end would have been greatly postponed at terrible cost of human life - American, Japanese and persons under Japanese occupation, who were dying in 1945 at the rate of 500,000 per month. Whatever Japan's postwar history would have been, it would not have resembled what it actually was.
All these things lay in the hands of fewer than 200,000 American, Canadian and British soldiers stepping onto French soil on one day. It was a burden that we should pray will never rest on human shoulders again.
End note: What of the atom bomb? It was originally envisioned for use against Naxi Germany, but Germany surrendered before the bomb was ready. With a lengthened war in Europe, could the atom bomb have restored US-UK fortunes there? I would argue that an expanded use the A-bomb from the two that actually were used is no victory. However it might have reestablished US power on the continent, such cannot be considered positively by any stretch of the imagination.