June 6, 1944, was the pivot of the 20th century. What had gone before that day led up to the invasion of France, and what followed was the consequence. At stake was the future of democracy. Fascism, communism, and democracy were locked in a death struggle that meant certain doom for one, if not two, of the competing ideologies. What was not certain was which one or ones.

At the beginning of June 1944, the Nazis were in control of the vast human and material resources of Europe, including big parts of Russia, but the Wehrmacht had failed to destroy the Red Army, which indeed was gaining strength daily and by this time had the Germans on the defensive. Hitler had the firepower to stop the Soviet advance, but only if he could concentrate his forces as Stalin was doing.

The Americans and British, meanwhile, were the only democracies in the world, and they had yet to play an important role in the European conflict. But they, too, had gathered strength and were ready to put their forces into a decisive struggle, beginning with the invasion.

If Hitler could stop that invasion, he would be free to move major forces from his western to his eastern front, enough perhaps to win a victory, almost certainly enough to impose a stalemate. Another consequence of failure on D-day would have been, probably, an immediate vote of no confidence in the presidential election for Franklin Roosevelt. (It is worth noting here that the United States was the only country to hold general elections during World War II.) The new governments would have a mandate to either prosecute the war more vigorously—which was hardly possible —or make an accommodation with the Nazis.

The same applied to the Soviet Union. If the long-anticipated and promised invasion failed, Stalin would have to attempt to make an even greater effort or—more likely because more possible—cut a deal with Hitler. He had, after all, done so in 1939. Either way—a Nazi-controlled Europe or a Europe split between the Communists and the Fascists—would be bad for democracy, possibly fatal.

“What if” history requires speculation. A “turning point” requires a genuine possibility that things could have gone the other way. So, did Hitler have any real reason to hope he could hurl back the Allies? Could the invasion have failed?

John Eisenhower says no. The son of the supreme commander is a respected military historian, and his view is that D-day can be compared to engineers building a bridge. The engineers are willing to guarantee that the bridge can carry a specified weight when they know that, in fact, it can carry twice as heavy a load. The Germans could not hold their coastal fortifications (the Atlantic Wall, as Hitler named it) against the firepower the Anglo-Americans could bring down on a single spot, and once ashore, the Allies had an immense follow-up force that would sooner or later prevail.

I say yes.