In 2006, agents of Al Qaeda, as well as those inspired by its ideology, continued their attacks. Violence in Iraq intensified, and Afghanistan saw its most violent year since 2001.

Despite worsening chaos on those fronts, counterterrorist forces arrested and killed high-profile terrorists and kept the West free from attack. But these actions don't appear to have weakened the appeal of Al Qaeda's agenda. "Home-grown" militants around the world joined its jihad, as regional fighting heightened perceptions of a global war on Islam.

Here's an assessment of some of the most significant gains and losses for Al Qaeda last year:

Terrorism experts say that militant jihadists shifted focus to the original Al Qaeda base to utilize experience and tactics gained in Iraq – as reflected in the increase in suicide bombings from 27 in 2005 to 139 in 2006, according to US estimates. Al Qaeda leader Osama bin Laden and his No. 2, Ayman al-Zawahiri, are widely believed to be hiding in the border region between Afghanistan and Pakistan.

Algeria's Salafist Group for Preaching and Combat declared an alliance with Al Qaeda in September.

In August, authorities foiled a terrorist plot with all the hallmarks of an Al Qaeda attack. British security arrested dozens of suspects whom they allege were participating in a plan to bomb up to 10 passenger flights from England to the US.

But Europe's major problem in 2006, experts say, was "home-grown terrorism." Britain's spy chief, Eliza Manningham-Buller, warned in November that the security service MI5 was "working to contend with some 200 groupings or networks, totaling over 1,600 identified individuals."

Europe is a primary recruiting base for Al Qaeda as Muslim communities there have access to wealth and freedom of movement, says Rohan Gunaratna, author of "Inside Al Qaeda: Global Network of Terror."

Islamic militants are "busy recruiting from the Muslim diaspora," adds Paul Wilkinson, chairman of the advisory board of the Centre for the Study of Terrorism and Political Violence at the University of St. Andrews in Scotland. "It's very clear that the organization is still very much in business.... And that recruitment has been going on quite rapidly."

An April 24 attack in a Sinai resort town was not claimed by Mr. bin Laden, but the hotel bombings had many similarities to an Al Qaeda strike. The attacks were a sign that the group's tactics have gained a foothold among other radical groups.

Hundreds of members of Jemaah Islamiyah (JI), a major terrorist group linked to Al Qaeda, were arrested, while more radical members split from the group in early 2006 to form Tanzim Qaedat al-Jihad. The biggest blow to counterterrorism efforts was the release of Abu Bakar Bashir from jail in June 2006 after he spent 26 months in prison. The radical Islamic cleric, who is said to lead JI, was cleared of conspiracy charges in December for his role in the 2002 Bali hotel bombings. "Indonesian counterterrorism law is gravely weak," says Mr. Gunaratna. "Abu Bakar Bashir is the leader of the most dangerous group in Southeast Asia. His group has killed more than 250 people."

The most violent offshoot of bin Laden's global organization, Al Qaeda in Iraq, seemed to suffer a major blow in 2006 with the killing of former chief Abu Musab al-Zarqawi in June.

But the loss of his leadership may have actually strengthened the group, says Gunaratna. "Zarqawi was a very able and ruthless man," he says, but "not a politician." His successor, Abu Ayyub al-Masri, "is following exactly the instructions of bin Laden and al-Zawahiri."

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