Of all the terrorist threats facing the United States, one stands in a category by itself. If al-Qaida set off a nuclear bomb in a U.S. city, there would be hundreds of thousands of casualties and a landscape uninhabitable for years to come.
A nuclear bomb is the one true weapon of mass destruction.
The likelihood of al-Qaida carrying out a nuclear attack involves two questions: First, does the group have the technical capability? And second, would it really want to use it?
As the top intelligence official at the Department of Energy, Rolf Mowatt-Larssen is the man in the U.S. government whose job it is to worry about nuclear terrorism.
He does not think al-Qaida has a nuclear bomb in its arsenal yet. Acquiring one would be a challenge.
A Pro And A Con
As for the group's thinking, Mowatt-Larssen imagines Osama bin Laden and other al-Qaida leaders sitting around a campfire somewhere in the mountains of Pakistan or Afghanistan, debating whether a nuclear attack on the United States would be a good idea.
"I could hear a pro and a con emerging from that discussion," Mowatt-Larssen says, with "some arguing that it would enhance, exalt the group's standing historically, others arguing that it would be a disaster."
Al-Qaida is sometimes portrayed as a terrorist group with an apocalyptic vision, intent mainly on destroying its enemies, without a focus on long-term goals of its own. But Mowatt-Larssen and other terrorism experts argue that it should be seen instead as acting strategically — at least from its own perspective.
A decision by al-Qaida leaders to carry out a nuclear attack would not be made lightly, he says.
"They would have to come to a conclusion, I believe, where they would justify the use of a nuclear or some other weapon of mass destruction in what they would consider rational terms," Mowatt-Larssen says. "In other words, how it would help them fulfill specific goals they have, which I think are well established."
Goals like destroying the U.S. economy, Mowatt-Larssen says, or shattering the United States' sense of security.
This idea — that Osama bin Laden, his deputy Ayman al Zawahiri and other al-Qaida leaders are proceeding thoughtfully — is gaining attention in intelligence circles.
An Intellectual Debate
Within the past year, Zawahiri in particular has allowed — even encouraged — an intellectual debate about how the radical Islamist movement should proceed. Most of it has been in the form of online discussions.
As research director at the center for combating terrorism at West Point, Jarrett Brachman has been following the al-Qaida comments.
"There have been a number of very important strategic writings, disseminated by the Internet, where they look at current American strategy and then they assess what their interests are and weigh the calculations," Brachman says. "Does this help them or hurt them? Does it help us or hurt us?"
Some Muslim readers who have weighed in on the Internet debate have actually challenged al-Qaida leaders over their use of terrorism, questioning whether it's morally acceptable under Islam.
Even those readers who sympathize with al-Qaida have wondered whether terrorist attacks serve al-Qaida's strategic interests.
There has been some debate within this group, for example, about whether the Sept. 11 attacks were a good idea in hindsight — given that they prompted the U.S. to go to war against al-Qaida in Afghanistan and destroy the group's sanctuaries there.
Brachman says such considerations may influence al-Qaida leaders as they consider whether to hit the U.S. again — and how hard.
"That type of example — that we will react violently if the cost to the United States is high enough — shapes the way they calculate whether or not to use weapons of mass destruction in the future," Brachman says. "There's a certain threshold of pain we're willing to accept, and if you exceed it we will respond aggressively. And I think they are trying to keep the pain that they're inflicting on us below a certain threshold at this point."
Acceptable Use Of A Nuclear Weapon
In 2003, a radical Saudi cleric did issue a fatwa, or religious edict, saying that the use of a nuclear weapon against the U.S. would be acceptable, even if it caused mass civilian casualties. But the fatwa has not been renewed in the five years since. Brachman says this may well reflect a deliberate calculation on the part of al-Qaida leaders.
"Using a nuclear device in the U.S., the strategists within al-Qaida know, would cause such a backlash that it may not actually be in their strategic interest to do that right now," Brachman says.
But neither Brachman nor other terrorism experts who monitor al-Qaida thinking can be certain what conclusions the group will reach.
Mowatt-Larssen says he is operating on the assumption that al-Qaida still intends to acquire a nuclear weapon — and to use it against the U.S.
"I personally think that even a terrorist group using a nuclear weapon would not be able to accomplish any objectives if they think through the problem properly," Mowatt-Larssen says. "It would plunge the world into a place that I believe ultimately would not serve al-Qaida's interests any more than it would serve a state who would use a nuclear weapon, but I'll to leave that up to al-Qaida. I do feel confident they have that intent, and that is the intent we worry about."