Hidden in the harsh terrain of Pakistan's tribal lands near the Afghan border, Al Qaeda's senior leaders have quietly been rebuilding their terrorist network – including lines of command to cells in other nations.
This resurgence does not mean the group has regained its old strength, say US intelligence officials and outside experts. Al Qaeda's top levels are now filled with inexperienced commanders, and its new camps can train only a fraction of the recruits the pre-2001 infrastructure in Afghanistan could handle.
Al Qaeda's goals also remain murky. It is not clear whether the organization has a specific plan to strike within the United States or whether it considers Europe, or Iraq, more important in its war to impose its vision of Islam on the Middle East.
"We have no evidence that they have a coherent strategy" to attack US targets, says Martin Libicki, lead author of a recently published RAND Corp. study on the subject.
The capabilities of a possibly resurgent Al Qaeda became a hot topic in Washington last week following Vice President Dick Cheney's surprise trip to Pakistan. During his visit, Cheney told Pakistani President Pervez Musharraf of US concerns that Al Qaeda is regrouping in Pakistan's tribal regions, and that the group's Taliban allies may mount a spring offensive into Afghanistan.
In a Senate hearing last week, US intelligence officials reiterated that terrorist groups remain their greatest challenge. Al Qaeda still tops the list of single threats.
"Its core elements are resilient," said the director of national intelligence, retired Vice Adm. Michael McConnell.
Al Qaeda would still like to inflict mass casualties upon the US, and it continues to seek weapons of mass destruction, Admiral McConnell said.
In addition, it is "forging stronger operational connections that radiate outward" from Pakistan to affiliated groups in the Middle East, North Africa, and Europe, according to US intelligence.
Still, Al Qaeda remains a loose network of like-minded individuals, instead of a tightly controlled terrorist hierarchy. Three-quarters of Al Qaeda's pre-9/11 leaders were killed or captured, according to US estimates. Aside from Osama bin Laden and his deputy Ayman al-Zawahiri, many of its leaders are relative rookies.
Nor has Al Qaeda's new Pakistani infrastructure replaced the multiple camps it operated in Afghanistan, capable of training thousands of recruits at once. "The numbers are not the same, but there are volunteers who are attempting to reestablish [training grounds]," McConnell said.
That Al Qaeda is resurgent in its remaining small corner of the world should not come as surprising news, some outside experts say.
"It's been true for a long time," says Jessica Stern, a terrorism expert at Harvard's Kennedy School of Government.
After all, US intelligence has long thought that Osama bin Laden disappeared into Pakistan's wild tribal frontier after the fall of the Taliban in Afghanistan. The area is so remote that for centuries it has largely remained beyond the control of central authorities. Border security is nonexistent.
As to evidence of Al Qaeda regaining its ability to reach out and mount attacks, in a videotape released last year Mr. Zawahiri claimed responsibility for the July 2005 London bombings. Similarly, investigators have long believed that last years' failed plot to blow up airliners from London was Al Qaeda-related, in part because it resembled a mid-1990s plan to explode airliners over the Pacific.
Some critics of the White House are surprised that many of the recent warnings about Al Qaeda come from administration officials. In essence, critics say, the White House confirms something they've long held to be true: the central front in the war on terror is along Pakistan's border with Afghanistan, not in Iraq.
"We went to Iraq and left the serious terrorist problem to fester," Ms. Stern says.
On the subject of Iraq and Al Qaeda, the Defense Intelligence Agency (DIA) estimates that less than 10 percent of the Iraqi insurgency consists of foreign fighters. Of those, most are suicide bombers.
Violence perpetrated by terrorists accounts for "only a fraction" of insurgent violence in Iraq, according to a written statement submitted to the Senate Armed Services Committee by DIA director Lt. Gen. Michael Maples. The attacks have a disproportionate impact on Iraq's stability because of the high-profile nature of the terrorist operations and tactics, the DIA says.
According to General Maples's statement, documents captured in a raid on a safehouse belonging to Al Qaeda in Iraq revealed that the group was planning operations in the US.
"Despite being forced to decentralize its network, Al Qaeda retains the ability to organize complex, mass-casualty attacks and inspire others," Maples wrote.
The DIA and other US intelligence sources maintain that Al Qaeda is still focused on striking the US. But that is not the same as having a specific plan or a discernable strategy for the goals it hopes to achieve by doing so, the RAND study says.
The study examined a number of hypothesis that might explain Al Qaeda's thinking with regard to hitting within the US: that the group's leaders might be interested in rallying supporters around the world or in coercing the US into leaving the Middle East.
The most likely scenario, RAND concluded, was that Al Qaeda would pick targets that would simultaneously create fear and damage the US economy. It might attack US agriculture or food industries, for instance; or employ radiological "dirty" bombs.
But, the study says, the terrorist organization itself has given few real clues about where or when it might strike, or if its leadership is even thinking in such terms, said the RAND study.