America's deadliest day transformed the war

The 140th anniversary of the Civil War battle of Antietam will occur on September 17. Most likely, it will not get much public notice. Partly (and understandably) this is because it will occur so soon after the commemorations of the September 11 terrorist attacks.

Nor is Antietam the best-known battle of the Civil War – that distinction surely goes to Gettysburg. And long-ago events often lose focus in our national consciousness. So to most contemporary Americans, Antietam has little meaning.

That's a shame because, according to Princeton historian James McPherson's wonderful new book, this indecisive, bloody battle fought near the small Maryland town of Sharspburg was the turning point of the Civil War.

Much of McPherson's book is devoted to the events that led to this battle. In early 1862, the Union forces scored a series of dramatic victories, and the confederacy verged on collapse. But General Robert E. Lee took control of the Army of Northern Virginia in June and the South's fortunes turned.

Within three months, the Confederates had seized the momentum by routing the Yankees in a series of battles that concluded with the Second Battle of Manassas in August.

The defeats came at a bad time for the Union. President Lincoln had already shelved his proposed Emancipation Proclamation so he could release it after a Union victory. Now, he wondered if that victory would ever come. At the same time, given the "war weariness" in the North, he worried about losing political control of the House of Representatives in the fall elections.

The British and French governments – with the enthusiastic support of the British press – talked openly about brokering a peace settlement that would have resulted in two countries. All they wanted was one more Confederate victory.

At this uncertain moment, General Lee's Army of Northern Virginia crossed the Potomac River and invaded Maryland, hoping to lure the Union troops into a decisive battle. General George McClellan's Army of the Potomac marched out of Washington to meet the Confederates.

Along the way, a Union enlisted man, stopping for a rest, found a bulky envelope that contained three cigars – and General Lee's battle plans. It was, according to McPherson, "a windfall such as few generals in history have enjoyed ... a remarkable example of the contingencies that change the course of history."

Even armed with Lee's plans, victory was no sure thing for the Union. McClellan was beloved by his troops, but he was an excessively cautious general and he almost waited too long to use the gift he had been handed.

The Battle of Antietam was, even by Civil War standards, unusually fierce. Roughly 6,400 Americans died there, making it, by far, the single bloodiest day in our history.

So devastating was the loss of life, notes McPherson, that "more American soldiers died at Sharpsburg (the Confederate name for the battle) than died in combat in all the other wars fought by this country in the 19th century combined."

Militarily, the battle was not decisive. The North prevailed on the battlefield, and the Confederates retreated. Eventually, Lee regained military momentum and reinvaded Maryland. The war dragged on for another two and a half years.

But the nonmilitary impact was much more decisive. Lincoln quickly announced the Emancipation Proclamation. This, notes McPherson, "changed the war from one to restore the Union into one to the destroy the old Union and build a new one purged of human bondage."

The proclamation changed the perception of the war in Europe. An American diplomat in the Netherlands wrote: "Everyone can understand the significance of a war where emancipation is written on one banner and slavery on the other."

Never again would foreign powers seriously consider recognizing the Confederacy. And the fall elections went Lincoln's way: While Democrats made significant gains in Congress, they were not enough to threaten Lincoln's leadership.

James McPherson is one of America's preeminent historians. "Battle Cry of Freedom," his one-volume history of the Civil War became a surprise bestseller and won the Pulitzer Prize in 1988.

In this slim volume, he skillfully weaves military, diplomatic, and political history into a seamless, highly readable narrative. This effort is intended for the general reader, not the academic expert, but the scholar's attention to precision and detail is evident on every page without overwhelming the text.

Books that deal with seminal events in American history while remaining faithful to historical scholarship and readable by laymen do not come along very often. But when they do, they should be read. History doesn't get any better than this.

• Terry W. Hartle is a senior vice president of the American Council on Education in Washington, D.C.