Charles Town, W.Va.

ONE hundred and fifty years ago today, the most successful terrorist in American history was hanged at the edge of this Shenandoah Valley town. Before climbing atop his coffin for the wagon ride to the gallows, he handed a note to one of his jailers: “I, John Brown, am now quite certain that the crimes of this guilty land will never be purged away but with blood.”

Eighteen months later, Americans went to war against each other, with soldiers marching into battle singing “John Brown’s Body.” More than 600,000 men died before the sin of slavery was purged.

Few if any Americans today would question the justness of John Brown’s cause: the abolition of human bondage. But as the nation prepares to try Khalid Shaikh Mohammed, who calls himself the architect of the 9/11 attacks, it may be worth pondering the parallels between John Brown’s raid in 1859 and Al Qaeda’s assault in 2001.

Brown was a bearded fundamentalist who believed himself chosen by God to destroy the institution of slavery. He hoped to launch his holy war by seizing the United States armory at Harpers Ferry, Va., and arming blacks for a campaign of liberation. Brown also chose his target for shock value and symbolic impact. The only federal armory in the South, Harpers Ferry was just 60 miles from the capital, where “our president and other leeches,” Brown wrote, did the bidding of slave owners. The first slaves freed and armed by Brown belonged to George Washington’s great-grandnephew.