WASHINGTON -- In the eight years since the Sept. 11 attacks, FBI Director Robert Mueller has spent nearly the entire time focused on one enemy: al-Qaeda.
Thousands of terrorist operatives have been killed or captured. Terrorist safe havens and training grounds in Afghanistan where operatives were trained have been destroyed. Military forces largely have shattered al-Qaeda's leadership in Iraq. Meanwhile, Osama bin Laden and top deputy Ayman al-Zawahri, who once closely managed al-Qaeda's day-to-day operations, have been driven into seclusion.
Now, Mueller and counterterrorism analysts are tracking the emergence of a new threat. Al-Qaeda has morphed into a fractured network of small terrorist franchises strewn across Asia, the Middle East and Africa. In Yemen, according to Senate testimony by Director of National Intelligence Dennis Blair, a "jihadist battleground" is rising amid growing political upheaval and poverty. Blair says there are concerns that al-Qaeda could establish a "regional base of operations" in Yemen to train operatives and plot new attacks against the West.
Al-Qaeda's transformation raises an unsettling question: Does its splintering help make the USA and its Western allies safer, or does it complicate efforts to guard against terrorism?
"Yes, they retain the capability of striking overseas," Mueller says in an interview, declining to specify whether the USA is vulnerable to such an attack. "They are still lethal."
Although al-Qaeda's pre-9/11 command structure no longer exists, its smaller terror cells are freer to conceive and direct their own operations, making them increasingly unpredictable. Several analysts worried about a terror resurgence cite evidence that pieces of al-Qaeda are gathering strength in Yemen and Somalia. Yemen's stability is especially crucial to U.S. interests because of its strategic location on the Arabian Peninsula, its access to critical shipping lanes and its vast border with the world's largest oil supplier, Saudi Arabia.
There is "growing concern that al-Qaeda will begin providing social and civil services to the people of Yemen on a scale that could challenge the Yemen government for allegiance," says Gregory Johnsen, a Yemen analyst based at Princeton University.
If al-Qaeda and its affiliates expand in Yemen and other weakened states, he says, the "danger to the U.S. is quite great."
Tom Fuentes, a former FBI assistant director who oversaw the bureau's Baghdad operations, says that "in one sense, you are safer because al-Qaeda no longer has that (pre-9/11) chain of command. On the other hand, al-Qaeda has become so decentralized, it can be harder to stop. … It's like a dormant volcano."
Other terrorism analysts, however, say government officials refuse to admit the threat al-Qaeda once posed largely has passed.
"The evidence is overwhelming," says Marc Sageman, a former CIA officer and prominent al-Qaeda analyst, citing his own analysis suggesting that al-Qaeda's capability to strike targets in the West is declining. "There is not much left of al-Qaeda except in the minds those inside the (Washington) Beltway."
Mueller says much of the danger now comes from a "genre" of hybrid groups spawned by the destruction of al-Qaeda safe havens. Separate groups, which share al-Qaeda's philosophy of eliminating Western influence from Muslim areas, have been inspired by al-Qaeda.
Among those groups, Mueller says, is the Pakistani militant organization Lashkar-e-Taiba, which he says is responsible for last November's attack in Mumbai, India, that killed 166 people.
Al-Qaeda-affiliated groups in Yemen claimed responsibility for two strikes against the U.S. Embassy in Sana last year. One was a coordinated assault last September that killed 17 people, including the six attackers.
"These guys think in terms of decades and centuries," says Phil Mudd, executive assistant director of the FBI's National Security Branch. "The challenge is whether you can keep the pressure on.
"… It's a shark's mouth," he says of al-Qaeda's resiliency. "You have to keep taking the teeth out again, and again. You can't allow the teeth to rotate to the front."
Not since al-Qaeda (Arabic for 'The Base') was formed 21 years ago after the Soviet Union's invasion of Afghanistan has the terrorist group faced so many questions about its viability, federal officials and analysts say.
It survived the destruction of its training bases. Yet the group's losses, especially the recent killings of senior al-Qaeda operatives, have created gaping holes in the "shark's mouth."
Among those killed by U.S. forces and allies:
• Rashid Rauf, mastermind of a failed 2006 plot to blow up trans-Atlantic airliners;
• Abu Khabab al-Masri, al-Qaeda's explosives expert;
• Usama al-Kini, linked by the FBI to the 2008 Marriott Hotel bombing in Islamabad that killed more than 60 people, including two Americans;
• Sheik Ahmed Salim Swedan, linked by the FBI to the 1998 bombings of the U.S. embassies in Kenya and Tanzania. The attacks killed 224 people, including 12 Americans.
"Al-Qaeda has taken more of a beating in the past year than at any time in the past five years," says Georgetown University professor Bruce Hoffman, who has examined terrorism for three decades. "But I haven't seen anyone deliver the knockout blow."
One of the reasons for the group's survival, Hoffman says, is its ability to adapt to pressure from U.S. and other forces.
Al-Qaeda's 20th anniversary last year was a reminder to its foes and followers that the group has created a lasting "brand," Hoffman says. At 20, al-Qaeda crossed a threshold formerly reached by terror groups such as the communist Revolutionary Armed Forces of Colombia, or FARC, Hezbollah in Lebanon and the Palestinian militant group Hamas. Even with bin Laden and Zawahri in seclusion, al-Qaeda has inspired new followers.
"Their greatest threat is in drawing people with clean Western passports" to become part of plots, Hoffman says, adding that there is recent evidence that up to 150 such Western converts have been attracted to al-Qaeda's ranks. "You're talking about people with the ability to fly under the radar (of terror profilers) with great ease."
But Sageman, the former CIA officer who last year was an adviser to New York's police department, believes al-Qaeda is closer to its end than a resurgence.
Not since the coordinated attacks on the London transit system, Sageman says, has the terrorist group shown the capability to strike targets in the West. The July 7, 2005, bombings of the subway and bus systems killed 56 people, including four bombers, and injured 700 others.
"Al-Qaeda has not been responsible for a single scratch (in the West) in more than four years," Sageman says. "Their training and leadership is a disaster." He says groups inspired by al-Qaeda are "mostly involved in local insurgencies."
In Iraq, where al-Qaeda operatives thrived after the 2003 U.S. invasion, Sageman says, public sentiment turned against the group two years ago, as Muslim civilian deaths mounted from repeated al-Qaeda attacks.
"Al-Qaeda simply overreached," Sageman says. "When they started killing heads of tribes, the tribes turned against them. … Al-Qaeda is dying."
Mueller acknowledges bin Laden's group has lost key commanders, but says its new leaders have "the ability to breathe new life into the organization."
In a telephone interview, Mueller says these new leaders are tapping recruits with planning or technical expertise to fill empty slots. To counter that, Mueller has tried to transform the bureau — part of larger, post-9/11 reorganization of federal law enforcement and intelligence agencies — to emphasize the prevention of new attacks, rather than to focus solely on prosecutions. Among the changes in the bureau since 9/11:
• The number of FBI agents assigned to counterterrorism or intelligence duties has more than doubled, from 2,514 to 5,419;
• The number of Joint Terrorism Task Forces has tripled, to 106 from 35, while the members of those task forces from federal, state and local agencies have soared, to 4,421 from 912;
• The number of intelligence analysts has more than doubled, to 2,511 from 1,023.
Mueller says the realignment of resources, the creation of the Department of Homeland Security and a greater emphasis on intelligence have helped avert attacks since 2001.
"We can no longer count on the oceans to protect us," he says.
On the crowded streets of Sana, Yemen, there is evidence that al-Qaeda is very much alive.
The attack last September on the U.S. Embassy in the Yemen capital underscored the growing concern among U.S. national security officials.
Yemen is fighting an escalating Shiite rebellion along its northern border, a secessionist movement in the south, rampant poverty and a shrinking water supply — all favorable conditions for al-Qaeda and its allies to recruit and train operatives, analysts say.
"Everything that allowed Saudi Arabia to largely defeat al-Qaeda — the big central government, wealth, religious message — doesn't exist in Yemen," says Christopher Boucek, a Middle East analyst with the Carnegie Endowment for International Peace. "It's a dangerous situation."
The country of 24 million people is the ancestral homeland of Osama bin Laden. Yemen's coastal city of Aden also was the scene of one of al-Qaeda's deadliest attacks against the United States: the 2000 bombing of the USS Cole, which killed 17 sailors.
A measure of U.S. concern has come in the past two months, as delegations of U.S. officials, including Gen. David Petraeus, the top U.S. commander in the Middle East, and Sen. John McCain, the Arizona Republican and former presidential candidate, have traveled to the Yemen capital to discuss the country's counterterrorism strategy.
Al-Qaeda's presence in Yemen also is at the center of a debate over what to do with 94 Yemeni prisoners set to be released from the Guantanamo Bay, Cuba, detention center when it closes in January 2010.
Yemen's government has said it expects the detainees to be returned home.
"The (Yemen) government acknowledges the challenges it faces," Yemen Embassy spokesman Mohammed Al-Basha says. "We have been open and transparent with our allies with regards to these challenges and continue to ask … for development and security assistance."
U.S. officials fear that allowing the prisoners to return home would add to the terrorist ranks.
"The government of Yemen has its hands full," says Sen. Lindsey Graham, R-S.C., who traveled with McCain and other senators to Sana last month. "It would be a poor policy decision to send these (detainees) back."
On Sept. 11, Mueller will be in his office, as he was when his mission changed the instant suicide hijackers hit their targets at the World Trade Center and the Pentagon and slammed into the Pennsylvania countryside.
"Sept. 11 will be another day that we make certain that it doesn't happen again," he says.
He worries that people have become "complacent" in the absence of additional attacks.
"We should lead our lives," the director says. "(But) there should be a depth of appreciation for what happened."