WASHINGTON – In the 1780s, the son of a farmer in south-central Pennsylvania purchased from his father 116 acres where two roads intersected. He laid out 210 lots for a town he named for himself. He was James Gettys.

What happened when two armies collided there 150 years ago was, some might argue, not the most important battle in American history or even in the Civil War. The 1777 defeat of the British at Saratoga won French support for the American Revolution. The Battle of Antietam (Sept. 17, 1862) enabled Abraham Lincoln to redefine the war by issuing the Emancipation Proclamation. The Battle of Midway sealed Japan’s fate.

But the Revolution would have succeeded without French assistance: No distant island could govern this continent. Japan’s defeat was assured when its attack on Pearl Harbor enraged a continental superpower. And in spite of Antietam, which repulsed the first invasion of the North, secession could still have succeeded if Robert E. Lee’s second invasion had shattered Northern support for the war by smashing the Union army at Gettysburg.

Antietam would have shortened the war, saving hundreds of thousands of lives, if Gen. George McClellan, among the most disagreeable figures in American history, had pursued the retreating Lee. But Antietam was most important for what it enabled Lincoln to proclaim 106 days later. Gettysburg was most important for what it achieved, not for giving the president an occasion to deliver an address there 139 days later.

Studying history serves democracy by highlighting contingencies: Things did not need to turn out the way they did; choices matter. Since Hegel, Marx and other 19th-century philosophers decided that history is History – a proper noun, an autonomous force unfolding an inner logic – humanity has been told that vast, impersonal forces dictate events, nullifying human agency.

But they don’t. Choices matter. They certainly did during the first three days of July 1863 at the town of 2,390 people seven miles north of the Mason-Dixon line. In “Intruder in the Dust,” William Faulkner famously invoked the tantalizing power of possibility:

“For every Southern boy fourteen years old, not once but whenever he wants it, there is the instant when it’s still not yet two o'clock on that July afternoon in 1863, the brigades are in position behind the rail fence. … That moment doesn’t need even a fourteen-year-old boy to think This time. Maybe this time with all this much to lose and all this much to gain: Pennsylvania, Maryland, the world, the golden dome of Washington itself.”

But before what is remembered as Pickett’s Charge – mostly a brisk 19-minute walk – headed toward Cemetery Ridge, choices made by Lee and some of his generals had put victory beyond the reach of valor. They were, however, choices.

Books about battles, historian Allen C. Guelzo says tartly, have “acquired among my academic peers a reputation close to pornography,” war being, in their eyes, chiefly a manifestation of American savagery. But, he says dryly, one cannot discuss the 19th century without discussing the Civil War era, whose “singular event was a war.” And one conducted, not least at Gettysburg, with an “amateurism” – a “bewildered, small-town incompetence” – that magnified its bloodiness.

The theory that it was the first “modern” or “total” war is, Guelzo acutely says, refuted by “the silent witness of places like Gettysburg, where almost all of the buildings that sat in the path of the battle are still [there]” because the technology of war was too limited to destroy them. A stray bullet killed just one civilian – Mary Virginia Wade, who picked a bad time to bake bread.

For those who Guelzo calls the war’s “cultured despisers,” the Union cause was mere dull democracy, whereas “emancipation makes a better story for our times.” But as Lincoln said at Gettysburg, the war’s ultimate purpose was to preserve the Union in order to prove democracy’s viability. “Unless the Union was restored,” Guelzo says, “there would be no practical possibility of emancipation, since the overwhelming majority of American slaves would, in that case, end up living in a foreign country, and beyond the possible grasp of Lincoln’s best anti-slavery intentions.”

Lee was, a colleague said, “audacity personified.” His temperament and intellect were mutually reinforcing, his aggressiveness serving his strategic understanding: The South would lose a protracted defensive war. After Antietam, Lee said: “If I could do so, I would again cross the Potomac and invade Pennsylvania.” Hence a small crossroads town became the hinge of American, and hence world, history.

© 2013, Washington Post Writers Group