Your imagination is rewarded, as the "What If?" question - professionally regarded as a "counterfactual" - is the basis of a book consisting of essays written by some of the top historians of our time, WHAT IF?: THE WORLD�S FOREMOST MILITARY HISTORIANS IMAGINE WHAT MIGHT HAVE BEEN, edited by Robert Cowley, a renowned World War I expert, who also writes an essay in the selection.

What If?: The Assyrians destroyed Jerusalem in 701 B.C.? The Persians defeated the Greeks at Salamis, 480 B.C.? Alexander the Great died before conquering the Middle East? The Roman Empire defeated the Germans at the Tuetoburg Forest, A.D. 9? The Dark Ages weren't so dark? Mongols conquered Europe in 1242? Henry VIII had not begun the Anglican Church, Ottomans lay waste to Eastern Europe in the 1520s? Cortes lost to the Aztecs, June 30, 1521? The Spanish Armada triumphed, August 8, 1588? The Americans' revolution was crushed? Napoleon hadn't been so foolish and refused to push into Russia? The Confederacy defeated the Federal troops at Antietam? The Great War had ended as soon as it began? Hitler conquered the Middle East instead of invading Russia? Japan won Midway? The U.S. and British arrived in Berlin before the Russians? Chiang Kai-shek hadn't gambled in 1946?

The idea spawns minds to run rampant, and is the story of many a Star Trek episode where alternated realities are explored. The introduction explains that professional historians use counterfactuals in literary circles "as a tool to enhance the understanding of history, to make it come alive."

What they mean, however, is that having a "�What If?" discussion is fun! It�s great to speculate about what might have been, and WHAT IF does so, ranging from conclusions as extreme as the non-existence of Western civilization as we know it, Christianity never reaching the masses as Islam spreads, or a Communist Europe where the U.S. is the weak superpower. That is, if the Confederacy didn�t successfully split the Union in 1863.

Such "What If?" scenarios are endless, and spirited conversations can carry on for weeks on just one of the counterfactuals. On the web billboard I frequent, I�ve had a now-20-page discussion on merely "what if England and France had entered the Civil War on the side of the Confederacy in 1862?" And we have yet to work out all the details on the synopsis.

As Cowley writes, "For historians, as the maxim goes, the dominos fall backward. In WHAT IF? We will attempt to make them fall forward."

When reading WHAT IF?, it is amazing how centuries can be decided by random luck due to weather, precious milliseconds of actions in battle, or the fallacies of ambitious men. From the first WHAT IF? where a plague may have saved the Jewish faith in 701 B.C., thus the future of Christianity as well, to the gamble of Chinese Nationalist leader Chiang Kai-shek that heightened tensions in the Cold War for decades and the uneasiness with Red China that permeates our government today.

Then there are the "second-order counterfactuals," in which the events may have transpired differently, but the end result would remain the same.

For example, if the United States had lost Midway in 1942, leaving the Pacific fleet in dire straits, that might have only driven us to use different means in defeating Japan. The use of the atomic bomb may have been used sooner, or used multiple times rather than just two in order to make our point to Japan and the Russians that Americans are no weaklings.

The historians don't overreach their subjects, suggesting improbable scenarios as "What If? World War I never began?" It was inevitable, so better to ask "What If? the British hadn't entered?" Only outcomes that were entirely possible are acceptable, such as a fog lifting for Washington at Brooklyn Heights, Robert E. Lee's Special Orders No. 191 never lost before Antietam or Alexander the Great saved from death by his aide in the second before an ax would have fallen on his skull in battle.

You see, WHAT IF? can keep history buffs busy for days, plotting different outlines of our existence, from an Islam-dominated planet to a Communist takeover of the U.S. or a Mexico still run by the Aztecs. That is, if the New World were discovered at all!