The 10th anniversary of the 9/11 attacks on the United States is likely to spur al-Qaida to redouble its efforts to instigate a big attack on U.S. and other Western targets, Western officials say.
But instead of directing a plot, its isolated and aging leaders will probably have to settle for the lesser role of inspirational figureheads who use personal or online ties to motivate allies with superior manpower and access to targets.
The capacity of al-Qaida leader Osama bin Laden to stage complex attacks like those of Sept. 11, 2001, has been relentlessly ground down by U.S. missile strikes in the remote northwest Pakistani mountains where he is believed to hide.
That is of limited comfort to Western governments.
Counter-terrorism specialists describe a constantly mutating movement that is harder to hunt than in its turn of the century heyday because it is increasingly diffuse -- a multi-ethnic, regionally dispersed and online-influenced hybrid of activists.
"Despite apparent weaknesses, the resilience of al-Qaida, and the tenacity of its various allies, have been outstanding," said Maha Azzam, Associate Fellow at Britain's Royal Institute of International Affairs.
"Counter-terrorism plans in the West and elsewhere are going to be increasingly challenged over 2011 because the threat is coming from different fronts and in different guises."
Experts suspect bin Laden would greatly prefer to oversee an attack, as this would be the best way to show his network remains relevant six years after its last successful strike in the West, the London bombings that killed 52 people in 2005.
But so diverse are today's global groupings of violent Islamist militants compared to a decade ago that such a plot is as likely to come from one of al-Qaida's growing array of allies as from its leadership, security officials and analysts say. "Ultimately, I expect it is the end game that matters most to bin Laden," said Henry Wilkinson, a senior analyst at Janusian security consultancy in London.
"If a major attack on the West occurred with or without al-Qaida involvement, he would probably view that as a success."
"And he would almost certainly receive credit as the inspiration anyway."
Weakened by drone strikes, the central leadership headed by bin Laden and his deputy Ayman al-Zawahri has been shorn of many of the mid-level experts they would need to mount a threat as complex as the 2001 airline hijack attacks that killed about 3,000 people in New York, Washington and Pennsylvania and triggered the U.S.-led "war on terror".
Making a virtue of necessity, the leaders appear to have hit upon a strategy of encouraging smaller, simpler attacks carried out by globally scattered hubs of sympathizers and affiliates in Africa, the Middle East, south and central Asia and Europe.
"The freelancers and offshoots are more important and potent than al-Qaida central," said Fawaz Gerges, professor of international relations at London's School of Oriental and African Studies.
Experts speculate that in some cases the leaders have had little choice but to cede operational control over their allies in return for the right to claim any operation for al-Qaida.
Willingness to attack
These hubs are supplemented by loose networks of so-called homegrown militants in the West, radicalized mostly online, which include U.S. citizens, experts say, and by an unknown number of individuals experts say could be willing to try solo attacks.
British Home Secretary Theresa May said in November threats did not now come just from "the old al-Qaida organization. Many other terrorist groups now aspire to attack us."
The evidence shows that al-Qaida's willingness to attack in the West is shared not only by affiliate groups, such as its Yemen-based al-Qaida in the Arabian Peninsula (AQAP), but also by like-minded militants such as Somalia's al-Shabaab and the Pakistan-based Pakistani Taliban, Lashkar-e-Taiba, and the mostly central Asian Taitaful Mansura and Islamic Jihad Union.
While al-Qaida central is a determined instigator and supporter of armed groups active in rampant militant violence in nuclear-armed Pakistan, its allies and sub-groups have shown they have a better chance of success in striking at the West, even if most plots to date have been foiled
A case in point is AQAP, which made failed attempts to bomb an airliner over Detroit in December 2009 and send parcel bombs to Chicago in October 2010, coming the closest of any part of al-Qaida to an successful attack on U.S. aviation since 2001.
In an article for the Site Intelligence Group, Bruce Hoffman, a veteran terrorism expert at Georgetown University, calls AQAP "the first credible competitor to its parent, al-Qaida Central, as the pre-eminent threat to American interests." (Additional reporting by Phil Stewart in Washington) (Editing by Angus MacSwan)