WASHINGTON — The plot for the Sept. 11 attacks was set in motion in late 1999 from a cluster of Al Qaeda training camps near Kandahar.
In those dusty Afghan compounds, Osama bin Laden and his lieutenants signed off on the plan, set up a special training program, and selected lead members of the hijack team.
Ten years later, could Al Qaeda return to Afghanistan and use it again as a launching pad for terrorist strikes?
The question has taken on heightened urgency as the Obama administration searches for a new war strategy, and Pakistan carries out its first major military offensive in the tribal region that Al Qaeda has called home since the U.S.-led invasion of Afghanistan in 2001.
The issue is also a source of surprising disagreement within the counter-terrorism community.
Some are skeptical that Al Qaeda would return to Afghanistan, even in the event of a substantial U.S. military drawdown. Doing so would mean leaving a sanctuary in Pakistan that has afforded significant protection for eight years, despite a barrage of U.S. Predator drone strikes.
Others argue that Al Qaeda is under mounting pressure in Pakistan, and that a return to Afghanistan is all but inevitable if President Obama endorses anything other than a full-scale, counterinsurgency campaign there.
The polarity of these positions helps to explain why, 10 months after taking office, Obama is still struggling to set a course for Afghanistan -- caught between the military's request for an additional 40,000 troops and calls to wind down the war in a country where Al Qaeda is no longer based.
Bruce Riedel, a CIA veteran who served as a White House advisor on Afghanistan earlier this year, said it was conceivable that Al Qaeda could be contained even while the U.S. ceded ground to Taliban militants. But there are substantial stakes.
"Do you want to bet the safety and security of the United States on [the] calculation that Al Qaeda wouldn't find a way back in?" Riedel said. "It's possible. But I think I might seriously consider moving out of metropolitan areas."
There is broad agreement among U.S. intelligence officials that Al Qaeda has a minimal presence in Afghanistan and would probably like to return there if it had the chance.
One senior U.S. counter-terrorism official said the number of Al Qaeda operatives in Afghanistan is in the "dozens," and that most function as low-level fighters with no significant leadership presence.
"Al Qaeda brings very little to the fight in Afghanistan," said the official, who spoke on condition of anonymity because of the sensitivity of the subject. Militarily, he said, "if you removed Al Qaeda from the equation in Afghanistan, it wouldn't matter."
That may be by design. Over the last eight years, Al Qaeda has burrowed deep into Pakistan's tribal belt, and fostered a closer relationship with local Taliban elements that are focused on carrying out attacks against the Pakistani government.
The Afghan Taliban, by contrast, has sought to distance itself from Al Qaeda, and to portray its insurgent campaign as a local fight.
A statement last month attributed to Taliban leader Mullah Mohammed Omar urged the West "not to be deceived" by Obama's assertions that the Afghanistan war is necessary because of the Al Qaeda threat. "The West does not have to wage this war," Omar said.
The message resonates with some senior counter-terrorism officials who argue that the Taliban learned its lesson after its ouster because of its alliance with Al Qaeda.
"I'm not sure that if the Taliban took over in Afghanistan that they would necessarily welcome Al Qaeda back," Richard Barrett, who heads the United Nations committee responsible for sanctions on Al Qaeda, said in a recent speech. "They perhaps don't want to make that same mistake again."
But others are skeptical that the Taliban would truly sever its Al Qaeda ties.
U.S. intelligence officials said there is little sign of an active relationship at the top of the organizations, and probably no contact whatsoever between Bin Laden and Omar.
Still, they point to ongoing coordination at lower levels. And in his recent military assessment, U.S. Army Gen. Stanley A. McChrystal said Al Qaeda aids the insurgency with "ideological motivation, training and financial support."
There are reasons that Al Qaeda might be reluctant to relocate. The protective, rugged terrain of Pakistan's Waziristan region and the group's ties with the tribes there offer advantages the terrorist network would struggle to replicate in other places such as Somalia or Yemen.
Pakistan has served as such an effective haven that after eight years, the trail for Bin Laden "is not just cold, it's frozen over," Riedel said.
Moving across the border would expose Al Qaeda operatives to risks of detection by satellites, CIA drones or spies on the ground. And even if the U.S. was to withdraw forces from Afghanistan, America is likely to have a substantial military presence there -- and freedom to operate, unlike in Pakistan -- for years to come.