Counterfactual history is making an ever larger contribution to historical thinking -- and is also winning favor with the history reading public. Two What If books edited by Robert Cowley, to which this writer contributed, have each sold over 100,000 copies and a third is in the works. In the current Journal of American History there is a fascinating article by Gary J. Kornblith about an alternative scenario that might have avoided the Civil War. An even bigger counterfactual proposition is waiting to be explored: What if the United States had not intervened in World War I?

If America had refused to intervene in 1917, would a German victory in 1918 have been a better historical alternative? That is debatable. By 1918, the Germans, exasperated by the Allies refusal to settle for anything less than "a knockout blow" (the words of Prime Minister David Lloyd George) were contemplating peace terms that would have been as harsh and vindictive as the ones the French and British imposed, with Woodrow Wilson's weary consent, in the Treaty of Versailles.

But there is another more promising alternative. What would have happened if Wilson had taken Secretary of State William Jennings Bryan's advice and practiced real rather than sham neutrality? Bryan wanted to bar both the Allies and the Germans from buying war materiel in the United States. Without the backing of American weaponry, munitions and loans, the Allies would have been forced to abandon their goal of the knockout blow. The war might have ended in 1915 or 1916 with a negotiated peace based on the mutual admission that the conflict had become a stalemate.

As a genuine neutral, Wilson might even have persuaded both sides to let him be a mediator. By 1917, the Germans, disgusted by America's huge arms sales to Great Britain, explicitly informed their ambassador to Washington that they did not want Wilson to play any part in peace negotiations. Meanwhile, canny Lloyd George had seduced Wilson with the argument that unless America intervened, the president would have no place at the peace table.

German aims before the war began were relatively modest. Basically, Berlin sought an acknowledgment that Germany was Europe's dominant power. They wanted an independent Poland and nationhood for the Baltic states to keep Russia a safe distance from their eastern border. Also on the wish list was a free trade zone in which German goods could circulate without crippling tariffs in France, Italy, Scandinavia and Austria-Hungary. It is not terribly different from the role Germany plays today in the European Union. But the British Tories could not tolerate such a commercial rival in 1914 and chose war.

Some people whose minds still vibrate to the historic echoes of British propaganda argue that by defeating Germany in 1918, America saved herself from future conquest by the Hun. The idea grows more fatuous with every passing decade. A nation that had suffered over 5,000,000 casualties, including almost two million dead, was not likely to attack the strongest nation on the globe without pausing for perhaps a half century to rethink its policies. One can just as easily argue that the awful cost of the war would have enabled Germany's liberals to seize control of the country from the militarists and force the Kaiser to become a constitutional monarch like his English cousin. A victorious Germany would have had no need of political adventurers such as Adolf Hitler. Nor would this counterfactual Germany have inserted the Bolsheviks into Russia and supported them with secret service money. Lenin and Trotsky would have agitated in a political vacuum in Switzerland unto a crabbed old age. Or ventured a revolution in their homeland that would have come to a swift and violent end. On the eve of the war, Russia had the fastest growing economy in Europe. The country was being transformed by the dynamics of capitalism into a free society. The war created the collapse that gave Bolshevism its seventy year reign of blood and terror.

The argument against intervention finds support from an unlikely, little known quarter. In 1935, President Franklin D. Roosevelt was as disillusioned witb the results of Woodrow Wilson's war as the rest of the American people. FDR told progressive Republican Senator Gerald Nye of Indiana that he now thought Secretary of State William Jennings Bryan was right -- Wilson's sham neutrality and his intervention in 1917 were mistakes. The president said the same thing in a letter to Wilson's secretary of the Navy, Josephus Daniels, around this same time. In August of 1936, Roosevelt said if another war broke out in Europe, it would be difficult to resist American businessmen who wanted to sell arms to the belligerents. But if America had to choose between profits and peace, "the Nation will answer -- must answer -- we choose peace." This was very close to a total repudiation of Woodrow Wilson's war by the man who had served in his administration and had been an ardent interventionist in 1917.

Why did Roosevelt become a covert interventionist after his election for a third term? It was a judgment call. By 1941 Adolf Hitler had achieved power beyond the Kaiser's wildest dreams. He had destroyed the French Army and driven the British Army back to England, a shattered remnant, and seemed on his way to conquering Soviet Russia. On the other side of the world, Hitler had allied Germany with a Japan that sought to dominate Asia. American security was profoundly threatened by this fascist world order. FDR decided it was his duty to intervene.