Terrorism's Harvest

U.S. forces hot on the trail of Osama bin Laden and the leaders of the Taliban in late 2001 didn't worry much about elderly, pious-looking men like Haji Juma Khan. A towering tribesman from the Baluchistan desert near Pakistan, Khan was picked up that December near Kandahar and taken into U.S. custody. Though known to U.S. and Afghan officials as a drug trafficker, he seemed an insignificant catch. "At the time, the Americans were only interested in catching bin Laden and [Taliban leader] Mullah Omar," says a European counterterrorism expert in Kabul. "Juma Khan walked."

That decision...