The Civil War battle in western Maryland that killed 22,000 men-and served no military purpose.

For generations of Americans, the word Antietam-the name of a bucolic stream in western Maryland-held the same sense of horror and carnage that the date 9/11 does for Americans today. But Antietam eclipses even this modern tragedy as America's single bloodiest day, on which 22,000 men became casualties in a war to determine our nation's future.

Antietam is forever burned into the American psyche as a battle bathed in blood that served no military purpose and brought no decisive victory. This much Americans know was true. What they didn't know was why the battle broke out at all-until now. The Cornfield: Antietam's Bloody Turning Point tells for the first time the full story of the struggle to control "the Cornfield," the action on which the costly battle of Antietam turned. Because Federal and Confederate forces...