George W. Bush led the United States into war in Iraq on the grounds that Saddam Hussein might give his country’s nonexistent weapons of mass destruction to terrorists. Now, Bush’s successor is perpetuating the war in Afghanistan with comparably dubious arguments about the danger posed by the Taliban and al Qaeda.

President Barack Obama insists that the U.S. mission in Afghanistan is about "making sure that al Qaeda cannot attack the U.S. homeland and U.S. interests and our allies" or "project violence against" American citizens. The reasoning is that if the Taliban win in Afghanistan, al Qaeda will once again be able to set up shop there to carry out its dirty work. As the president puts it, Afghanistan would "again be a base for terrorists who want to kill as many of our people as they possibly can." This argument is constantly repeated but rarely examined; given the costs and risks associated with the Obama administration’s plans for the region, it is time such statements be given the scrutiny they deserve.

Multiple sources, including Lawrence Wright's book The Looming Tower, make clear that the Taliban was a reluctant host to al Qaeda in the 1990s and felt betrayed when the terrorist group repeatedly violated agreements to refrain from issuing inflammatory statements and fomenting violence abroad. Then the al Qaeda-sponsored 9/11 attacks -- which the Taliban had nothing to do with -- led to the toppling of the Taliban’s regime. Given the Taliban’s limited interest in issues outside the "AfPak" region, if they came to power again now, they would be highly unlikely to host provocative terrorist groups whose actions could lead to another outside intervention. And even if al Qaeda were able to relocate to Afghanistan after a Taliban victory there, it would still have to operate under the same siege situation it presently enjoys in what Obama calls its "safe haven" in Pakistan.

The very notion that al Qaeda needs a secure geographic base to carry out its terrorist operations, moreover, is questionable. After all, the operational base for 9/11 was in Hamburg, Germany. Conspiracies involving small numbers of people require communication, money, and planning -- but not a major protected base camp.

At present, al Qaeda consists of a few hundred people running around in Pakistan, seeking to avoid detection and helping the Taliban when possible. It also has a disjointed network of fellow travelers around the globe who communicate over the Internet. Over the last decade, the group has almost completely discredited itself in the Muslim world due to the fallout from the 9/11 attacks and subsequent counterproductive terrorism, much of it directed against Muslims. No convincing evidence has been offered publicly to show that al Qaeda Central has put together a single full operation anywhere in the world since 9/11. And, outside of war zones, the violence perpetrated by al Qaeda affiliates, wannabes, and lookalikes combined has resulted in the deaths of some 200 to 300 people per year, and may be declining. That is 200 to 300 too many, of course, but it scarcely suggests that "the safety of people around the world is at stake," as Obama dramatically puts it.

In addition, al Qaeda has yet to establish a significant presence in the United States. In 2002, U.S. intelligence reports asserted that the number of trained al Qaeda operatives in the United States was between 2,000 and 5,000, and FBI Director Robert Mueller assured a Senate committee that al Qaeda had "developed a support infrastructure" in the country and achieved both "the ability and the intent to inflict significant casualties in the U.S. with little warning." However, after years of well funded sleuthing, the FBI and other investigative agencies have been unable to uncover a single true al Qaeda sleeper cell or operative within the country. Mueller's rallying cry has now been reduced to a comparatively bland formulation: "We believe al Qaeda is still seeking to infiltrate operatives into the U.S. from overseas."

Even that may not be true. Since 9/11, some two million foreigners have been admitted to the United States legally and many others, of course, have entered illegally. Even if border security has been so effective that 90 percent of al Qaeda’s operatives have been turned away or deterred from entering the United States, some should have made it in -- and some of those, it seems reasonable to suggest, would have been picked up by law enforcement by now. The lack of attacks inside the United States combined with the inability of the FBI to find any potential attackers suggests that the terrorists are either not trying very hard or are far less clever and capable than usually depicted.

Policymakers and the public at large should keep in mind the words of Glenn Carle, a 23 year veteran of the CIA who served as deputy national intelligence officer for transnational threats: "We must see jihadists for the small, lethal, disjointed and miserable opponents that they are." Al Qaeda "has only a handful of individuals capable of planning, organizing and leading a terrorist operation," Carle notes, and "its capabilities are far inferior to its desires."

President Obama has said that there is also a humanitarian element to the Afghanistan mission. A return of the Taliban, he points out, would condemn the Afghan people "to brutal governance, international isolation, a paralyzed economy, and the denial of basic human rights." This concern is legitimate -- the Afghan people appear to be quite strongly opposed to a return of the Taliban, and they are surely entitled to some peace after 30 years of almost continual warfare, much of it imposed on them from outside.

The problem, as Obama is doubtlessly well aware, is that Americans are far less willing to sacrifice lives for missions that are essentially humanitarian than for those that seek to deal with a threat directed at the United States itself. People who embrace the idea of a humanitarian mission will continue to support Obama's policy in Afghanistan -- at least if they think it has a chance of success -- but many Americans (and Europeans) will increasingly start to question how many lives such a mission is worth.

This questioning, in fact, is well under way. Because of its ties to 9/11, the war in Afghanistan has enjoyed considerably greater public support than the war in Iraq did (or, for that matter, the wars in Korea or Vietnam). However, there has been a considerable dropoff in that support of late. If Obama's national security justification for his war in Afghanistan comes to seem as spurious as Bush's national security justification for his war in Iraq, he, like Bush, will increasingly have only the humanitarian argument to fall back on. And that is likely to be a weak reed.