Nearly 10 years after Osama bin Laden declared war on the United States, America may be fighting not just one Al Qaeda, but many Al Qaedas, spread all over the globe.
The physical nodes of this network remain highly vulnerable to attack. That's shown by last week's arrest of 17 alleged home-grown jihadis in Canada, plus the death of the notorious Abu Musab al-Zarqawi in a US airstrike in Iraq.
But the beliefs that inspired these men are far more difficult to counter. Both the Canadian cell and Mr. Zarqawi were self-motivated - not direct recruits of the bin Laden organization.
Experts say it thus may be important to remember that the biggest threat from Al Qaeda is not its people, but its ideas, and the manner in which they inspire the disaffected and angry in Muslim communities worldwide.
"With these groups unconnected to Al Qaeda, it is really hard [to counter them]," says Michael Scheuer, former head of the Osama bin Laden group at the CIA. "If they are only inspired by them, how do you handle it? Instead of facing a main enemy, you are facing dozens of enemies."
To be sure, the events of recent days may represent a real victory for the world's counterterrorism forces.
In Canada, security forces may have rolled up a terror cell with connections in the US, if allegations made in court papers prove true. Some of the Canadian detainees allegedly met with two US nationals from Georgia who are currently facing federal terrorism-related charges in the US.
And police in northern England arrested two terror suspects - one only 16 years old - in raids Thursday that the BBC said were connected to the Canadian investigation.
Meanwhile, the death of Zarqawi eliminates a terror figure who was both an inspiration to many Iraqi insurgents and a leader so brutal that the Al Qaeda leadership tried, without apparent success, to rein him in.
US intelligence believes Zarqawi personally participated in the beheading of some hostages.
"He was a truly terrifying individual," says David Brannan, a specialist on terror at the Naval Postgraduate School in Monterey, Calif., and an adviser to the Interior Ministry in Iraq in 2003 and 2004.
Mr. bin Laden and other top Al Qaeda officials outside Iraq will probably have mixed feelings about Zarqawi's fate, says Mr. Brannan. His actions made it easier to depict the Iraqi insurgency as cruel. He had a hatred of Shiite Muslims that other terror leaders might have found unproductive. And his public image at times threatened to overshadow that of bin Laden himself.
"I'm sure they're not glad he's dead, but I'm sure they were concerned about his sort of charismatic leadership," says Brannan.
US forces' successful targeting of Zarqawi indicates that their intelligence dealing with the insurgency is getting better, add other experts. That's important, because counterinsurgency is as much a war of tips, informants, and information as it is a war of force.
"This was an incredible intelligence coup, and [one] that will have profound repercussions because Zarqawi's cell will have to wonder what other traitors are in their midst," says Bruce Hoffman, a RAND Corp. terrorism expert whose 1998 book "Inside Terrorism" has just been updated and re-released.
But overall, the Al Qaeda jihad has become so decentralized that eliminating its leaders is unlikely to eliminate its violence, Mr. Hoffman adds.
The alleged Canadian cell had no apparent direct connection with Al Qaeda's leadership. Similarly, the terrorists who exploded a bomb in Madrid's Atocha train station in 2004, and those who attacked London's transit system in 2005, were homegrown operations.
As far afield as Nigeria and Bangladesh, local Islamist firebrands claim inspiration from bin Laden, according to Mr. Scheuer.
And that may be what bin Laden planned. "These groups weren't ordered, directed, or managed by Al Qaeda, but they were inspired by Al Qaeda," says Scheuer. "For the West, that is a very worrisome development: Osama bin Laden has always seen his goal as a chief instigator, and [in that] he is succeeding."
The fight he aims to instigate may not be total war against the US. Bin Laden has never claimed Al Qaeda could defeat the US, or destroy Western civilization, according to Scheuer. Instead, he has limited his goals to forcing the US and its allies to leave the Middle East, via a gradual increase in attacks. Al Qaeda and its allies could then turn themselves toward their final goal: the elimination of most current Arab regimes and the state of Israel, and the institution of an Islamic caliphate throughout the region.
Al Qaeda would definitely need allies. Bin Laden has long said that his group should simply serve as the vanguard of a broad-based Islamist movement.
"The reality is that he has never sought universal command-and-control and has always tried to foment widespread, anti-Western Islamist violence that would need nothing from al-Qaeda except for inspiration," writes Scheuer in a recent article in the journal Terrorism Focus.