From a review of Michael Kazin’s War against War: The American Fight for Peace:
Kazin even offers a counterfactual perspective on the outcome of World War I without U.S. intervention. The war would have continued, and it might have been 1919 or 1920 before civilian pressure forced Europe’s leaders to the negotiating table. The result would have been a more moderate peace settlement, rather than the dictated arrangement reached at Versailles. Both the circumstances that bankrupted the Weimar Republic and the rise of Hitler would have been avoided, and thus there would have been no Second World War (xv–xvi). Instead, we know the outcomes of 1917–1919, and what David Fromkin called “the peace to end all peace.”
This is reminiscent of H. L. Mencken who wondered what would have happened had the Union not prevailed in the Civil War:
No American historian, so far as I know, has ever tried to work out the probable consequences if Grant instead of Lee had been on the hot spot at Appamattox. How long would the victorious Confederacy have endured? Could it have surmounted the difficulties inherent in the doctrine of States’ Rights, so often inconvenient and even paralyzing to it during the war? Could it have remedied its plain economic deficiencies, and become a self-sustaining nation? How would it have protected itself against such war heroes as Beauregard and Longstreet, Joe Wheeler and Nathan D. Forrest? And what would have been its relations to the United States, socially , economically, spiritually and politically?
I am inclined, on all these counts, to be optimistic. . . . If the war had gone with the Confederates no such vermin would be in the saddle, nor would there be any sign below the Potomac of their chief contributions to American Kultur—Ku Kluxry, political ecclesiasticism, nigger-baiting, and the more homicidal variety of wowserism. Such things might have arisen in America, but they would not have arisen in the South. The old aristocracy, however degenerate it might have become, would have at least retained sufficient decency to see to that. New Orleans, today, would still be a highly charming and civilized (if perhaps somewhat zymotic) city, with a touch of Paris and another of Port Said. Charleston, which even now sprouts lady authors, would also sprout political philosophers. The University of Virginia would be what Jefferson intended it to be, and no shouting Methodist would haunt its campus. Richmond would be, not the dull suburb of nothing that it is now, but a beautiful and consoling second-rate capital, comparable to Budapest, Brussels, Stockholm or The Hague. And all of us, with the Middle West pumping its revolting silo juices into the East and West alike, would be making frequent leaps over the Potomac, to drink the sound red wine there and breathe the free air.
My guess is that the two Republics would be getting on pretty amicably. Perhaps they’d have come to terms as early as 1898, and fought the Spanish-American War together. In 1917 the confiding North might have gone out to save the world for democracy, but the South, vaccinated against both Wall Street and the Liberal whim-wham, would have kept aloof—and maybe rolled up a couple of billions of profit from the holy crusade. It would probably be far richer today, independent, than it is with the clutch of the Yankee mortgage-shark still on its collar. It would be getting and using his money just the same, but his toll would be less. As things stand, he not only exploits the South economically; he also pollutes and debases it spiritually. It suffers damnably from low wages, but it suffers even more from the Chamber of Commerce metaphysic.
No doubt the Confederates, victorious, would have abolished slavery by the middle of the 80s. They were headed that way before the war, and the more sagacious of them were all in favor of it. But they were in favor of it on sound economic grounds, and not on the brummagem moral grounds which persuaded the North. The difference here is immense. In human history a moral victory is always a disaster, for it debauches and degrades both the victor and the vanquished. The triumph of sin in 1865 would have stimulated and helped to civilize both sides. (“The Calamity of Appomattox,” 1930)
Commemorating war may include remembering that its outcome, like the rest of history, is hardly inevitable.