Into Thin Air

When the United States struck Afghanistan in 2001, "there were probably 3,000 core Al Qaeda operatives," says Arquilla of the Naval Postgraduate School. "We killed or captured about 1,000; about 1,000 more ended up in distant parts of the world. And about 1,000 ended up in Waziristan. But the great terror university in Afghanistan is gone; they've relied on the Web since. They haven't had the hands-on instruction and the bonding of the camps. That's resulted in low-skill levels. Their tradecraft is really much poorer."

The danger now, says Arquilla, is that the longer the Iraq War goes on, the more skilled the new generations of jihadists will become. "They're getting re-educated," he says. "The first generation of Al Qaeda came through the [Afghan] camps. The second generation are those who've logged on [to Islamist Web sites]. The next generation will be those who have come through the crucible of Iraq. Eventually, their level of skill is going to be greater than the skill of the original generation."

It is disturbing to recall that when U.S. forces overran Qaeda training grounds, they found scientific documents discussing nuclear, chemical and biological weapons. (Zawahiri is reported to have a particular interest in chem-bio.) A true weapon of mass destruction is very hard to come by, and it may be a while before the jihadists can make, steal or buy a nuclear weapon or a germ bomb capable of killing more than a few people. But dirty bombs are less difficult to craft from conventional explosives and radioactive material, the kind that can be found in the waste bins of hospitals. Crumpton recalls that Zawahiri canceled a planned attack to set off a cyanide bomb in the New York City subways in 2003. "We don't know why," says Crumpton, or what became of the team Al Qaeda recruited to stage the attack but apparently never dispatched to the United States. "You think: Why did he call it off? Where are they?"

Intelligence officials in Europe and America have spent a jittery summer seeing signs that Al Qaeda is gearing up to hit the West in some significant way. In his interview with NEWSWEEK, Admiral Redd of the National Counterterrorism Center was guarded about details. But it was clear from his comments that the terror watchers are seeing signs and hearing chatter that have put them on alert. For an attack on Europe? America? "They would like to come west, and they would like to come as far west as they can," is how Redd puts it. The intelligence community lacks specific information about the movements of terrorists, he said. "What we do have, though, is a couple of threads which indicate, you know, some very tactical stuff, and that's what—you know, that's what you're seeing bits and pieces of, and I really can't go much more into it."

Meanwhile, the hunt for bin Laden goes on. Recently, it has gone all the way back to the beginning—to the Tora Bora region. This summer, about 500 jihadists—Taliban and Al Qaeda, increasingly indistinguishable—infiltrated the area. After three American Special Forces soldiers were killed by a roadside bomb in early August, the Americans launched a sweep of bin Laden's old hideout, backed by aerial strikes. Last week a NEWSWEEK reporter, led by a guide, hiked up into the mountains to visit the battlefield.

On the way up, they passed small convoys of American Humvees and Afghan National ArmyFord Ranger pickups. Along the trail, past a few dozen unmarked Arab graves from the 2001 bombing, they saw bits of shrapnel, corroded bullets and scraps of military detritus, some of it quite old. Leaflets blew around. They warned the locals that American troops would hunt down people who sheltered terrorists. On the leaflets were garish pictures of evil-looking masked men with glaring white eyes; one had the word OSAMA in a red circle with a diagonal slash through it.