The events recently witnessed are of an enormity that is almost beyond comprehension. We have experienced—are experiencing—a national trauma that will take a long time to heal. The resiliency of our institutions and our society are being sorely tried. But they have been tried before and have survived, indeed have emerged from the trauma stronger and better than before.

The greatest trial occurred 140 years ago, in the Civil War. Some 610,000 Americans lost their lives in that conflict. This ghastly toll was 2 percent of the American population at the time. If 2 percent of the American people were to lose their lives in a war fought today, the number of American war dead would be five and a half million. On another cataclysmic September day 139 years ago, September 17, 1861, 6000 soldiers were killed outright or mortally wounded in the Battle of Antietam. September 17, 1861 was the bloodiest day in American history before the horrible events of September 11, 2001.

In 1862, as today, Americans sought an explanation for such terrible carnage. What could justify the bloodletting of the Battle of Antietam? In retrospect, we know that it provided President Abraham Lincoln with the occasion to announce his Emancipation Proclamation, a crucial step in the process by which four million slaves achieved freedom and the institution of slavery, which had divided and disgraced America, was abolished forever. The Battle of Antietam also proved to be a critical turning point toward ultimate Union victory in the Civil War, a victory that preserved the United States as one nation, indivisible.

But it did more than preserve a united nation. It kept alive the vision of a democratic political order and of a republican form of government. That vision itself was on trial in the Civil War. The United States stood almost alone in the mid-19th century as a democratic republic in a world bestridden by kings, queens, princes, emperors, czars, and petty dictators. Despite the anomaly of slavery in a land that boasted of liberty, champions of human rights in other countries looked to the United States, in the words of one of them, as a “beacon of freedom.”

Secession and civil war threatened to extinguish this beacon. The forces of reaction in Europe responded with expressions of smug satisfaction at the “immortal smash” of the now dis —United States as proof, in the words of one British aristocrat, of “the failure of republican institutions in time of pressure.” During a bleak period for the Union cause, the Conservative British leader Benjamin Disraeli said the United States could never be brought together again: America of the future “will be an America of rival states and maneuvering Cabinets, of frequent turbulence, and of frequent war.”

But, even in the grim June of 1862, President Lincoln declared his intention “to maintain this contest until successful, or till I die, or am conquered, or my term expires, or Congress or the country forsake me.” He did maintain the contest until successful, but he