When I was eleven or twelve years old, I discovered, in the little library that served the Cape Cod town of Dennis, where I was spending the summer, a book about the turn-of-the-century— this century—war between Britain and France. The pictures drew me in: an invasion force wading ashore in the south; British rifle companies breaking up French cavalry assaults on the London road; the Kentish countryside in flames. Channel fighting! Dreadnoughts and destroyers and torpedo boats in a great promiscuous close-packed muddle, hammering it out nearly hull to hull.

I read the book with fascination. I don’t recall ever wondering why nobody seemed to have taken photographs of these interesting events; the grisaille illustrations were perfectly satisfying. I believed in this Anglo-Franco war for an embarrassingly long time and may well have gone into high school still wondering how the two countries had come to patch things up to the point where they could fight side by side as allies a mere decade later.

On my behalf, I would say that the Dennis librarian believed in the war, too; the book resided in the history section, bearing the appropriate Dewey classification. And the fact is that it could have happened. A century ago, a good part of the British population believed that, when the big war came, it would be with their traditional enemy.

That book belonged to a literary genre that has been with us nearly as long as the novel itself and that is just now enjoying particularly vigorous growth. In this issue, Phil Patton explores why alternate history has become so popular, and Fredric Smoler picks some of the most telling current examples, while James McPherson offers one of his own, in which the Confederacy fares quite differently.

This sort of exercise (long despised in the academy, although not so much now that it can be ennobled with the term counterfactual ) is a useful way of looking at history. Not in every form, of course. Some of the literature is the sort of boilerplate Donald Westlake takes a swipe at in his novel God Save the Mark, when his hero meets a man who has just put the final touches to the manuscript of his book Veni Vidi Vici Through Airpower. It posits that Julius Caesar had fighter planes on the World War I level during his campaigns. Well, Westlake’s hero says, that would mean changes throughout Roman society: petrochemical industry, machine tools, electricity. No, the writer isn’t interested in any of that, just in imagining the cohorts going into battle with biplanes buzzing overhead. What would be changed then? Well, actually, the author admits, not so much. After all, Caesar won most of the battles he fought.

But when gifted and imaginative writers bring their skills to bear on exploring a world that might have been, the results can be thrilling, because they strike a universal chord. Just as every individual’s life