In Afghanistan, heroin has become the Devil’s cocktail. “Smack” is already one of the most addictive and destructive drugs on Earth, and now numerous academic studies show addiction levels on the rise, particularly among younger children. In the place where 90 percent of the world’s heroin supply originates, the Taliban, al Qaeda, and others harvest profits from opium poppy cultivation to buy weapons and equipment used to attack soldiers and civilians engaged in a mostly stalled reconstruction mission. A reverse symbiosis is at work: Those who benefit most from the opium/heroin trades also benefit most from a destabilized Afghanistan, because...