One hundred fifty years ago today, two great armies clashed in a titanic struggle that would decide the fate of a nation. "Around a cornfield and a little white Dunker church, around a stone bridge and in a pasture lane worn by cow paths, surged a human tornado," wrote Carl Sandburg many years later. Never before or since has such a deadly concentration of firepower been unleashed on the American continent.

The Battle of Antietam, waged across a meandering stream called Antietam Creek in Western Maryland near Hagerstown, was the first great turning point of the American Civil War and the bloodiest single day of combat ever waged on U.S. soil. When the guns finally fell silent toward that evening, some 25,000 Union and Confederate troops lay dead, wounded or missing, and the country would never be the same again.


Until the federal Army of the Potomac, led by Union Gen. George B. McClellan, and Gen. Robert E. Lee's Confederate Army of Northern Virginia met on Sept. 17, 1862, in the broad valley between South Mountain range and a wild, looping curlicue of the Potomac River, the war had been largely a sectional dispute between competing economic interests in the slave-holding South and the industrial North.

After Antietam, it became a moral crusade to realize an ideal of American democracy that was then still struggling to be born, and which a century and a half later we have yet to perfect.

Antietam revealed to both sides the staggering sacrifice each would be required to make in order to prevail. The fighting that day was savage, crazed, unspeakably cruel. On both sides, entire regiments — 1,000 men or more — were wiped out in minutes, and their replacements fell just as quickly on blood-soaked earth carpeted with the bodies of their comrades.

Gen. George Hooker, who led the first Union assault on the Confederate lines, was astounded by the ferocity of the fighting: "Every stalk of corn in the northern and greater part of the field was cut as closely as could have been done with a knife," he recalled, "and the slain lay in rows precisely as they had stood in their ranks a few moments before."

Historians rate the outcome of the battle a draw. The following day found both armies utterly exhausted. Lee's plan to invade the North as far as Harrisburg, Pa., and cut the B&O rail line there connecting Washington to the West had been checked. But McClellan was unable to exploit the advantage he held in troops and equipment. As a result, on Sept. 18, Lee was allowed to retreat back into Virginia unmolested, despite President Lincoln's urgent messages to McClellan demanding he pursue and crush the enemy. Had McClellan done so, the war might well have ended years earlier than it did.

For the president, however, even a partial victory represented an opportunity. Five days after the battle, on Sept. 22, 1862, he issued the Emancipation Proclamation ending slavery in all the states of the Confederacy. Fully as much as the Declaration of Independence and the U.S. Constitution, that transformative edict, in the words of historian Benjamin Quarles, "was destined to take on the evocative power reserved only for the half-dozen great charter expressions of human liberty in the entire Western tradition."

Antietam enabled Lincoln to identify the nation's cause with the cause of liberty for men and women everywhere and at all times, and had it not occurred, it is quite possible that America never would have become the beacon of freedom the world now recognizes. That is why on this day we pause to honor the legacy of its terrible blood and suffering, which a century and a half later remains a cornerstone of the more perfect union we are still engaged in building.