As U.S. helicopters approached in darkness a year ago, Osama bin Laden was woefully unprepared: no means of escape, no way to destroy files, no succession plan.

But U.S. intelligence analysts scouring the trove of data he left behind continue to find evidence that al-Qaeda was making provisions for the long term, plans that in some cases remain on track.

Among the previously undisclosed records is a lengthy paper by bin Laden’s successor, Ayman al-Zawahiri, laying out the al-Qaeda strategy for Afghanistan in the years after the United States withdraws, current and former U.S. officials said.

Other files show that through his couriers, bin Laden was in touch not only with al-Qaeda’s established affiliates but also with upstarts being groomed for new alliances. Among them was Nigeria’s Boko Haram, a group that has since embraced al-Qaeda and adopted its penchant for suicide attacks.

Tracing clues in the trove against developments of the past year has been a focal point for U.S. counterterrorism officials seeking to assess what has become of al-Qaeda since the U.S. Navy SEAL raid on bin Laden’s compound in Abbottabad, Pakistan.

The emerging picture is of a network that is crumpled at its core, apparently incapable of an attack on the scale of Sept. 11, 2001, yet poised to survive its founder’s demise.

U.S. officials have debated “since bin Laden’s death what is the trajectory of this organization and when will we know that we’ve actually defeated it,” a senior U.S. counterterrorism official said.

The answer so far is split.

“The organization that brought us 9/11 is essentially gone,” said the official, among several who spoke on the condition of anonymity to discuss U.S. intelligence assessments of al-Qaeda with reporters a year after bin Laden was killed. “But the movement . . . the ideology of the global jihad, bin Laden’s philosophy — that survives in a variety of places outside Pakistan.”

That assessment is considerably more measured than some that were offered in the afterglow of the raid in Abbottabad. Most notably, Leon E. Panetta, after leaving his post as CIA director to become secretary of defense, said he was “convinced that we’re within reach of strategically defeating al-Qaeda.”

That prospect seemed to grow more tantalizing through the remainder of last year, as CIA drones picked apart al-Qaeda’s upper ranks.

Among those killed in the flurry of strikes were Ilyas Kashmiri, an operative bin Laden tasked with finding a way to kill President Obama, and Atiyah Abdul Rahman, who was in day-to-day charge of al-Qaeda and served as the main link between bin Laden and the network he built.

When a CIA drone killed Anwar al-Awlaki, the U.S.-born cleric accused of helping al-Qaeda’s affiliate in Yemen plot attacks, even the network’s most aggressive franchise seemed suddenly vulnerable.

Since then, however, the momentum has slowed, and al-Qaeda has maneuvered past problems that U.S. officials hoped would hasten its demise. Zawahiri, for example, has defied predictions that he would fail to hold al-Qaeda together without bin Laden to safeguard the brand.

U.S. officials still describe Zawa­hiri as a divisive figure who lacks bin Laden’s charisma. He is “less compelling,” Robert Cardillo, deputy director of national intelligence, said in a conference call with reporters to discuss the status of al-Qaeda. The group’s followers “will not offer and have not offered [Zawahiri] the deference provided bin Laden.”

Still, no rivals to Zawahiri have emerged. And instead of coping with defections, Zawahiri has added groups to the al-Qaeda fold.

“I don’t think he’s been the disaster people expected,” said Bruce Hoffman, a counterterrorism expert at Georgetown University. Noting that al-Shabab, a militant group in Somalia, formally joined al-Qaeda just two months ago, Hoffman said, “terrorist groups don’t hitch themselves to falling stars.”

Under Zawahiri, a bespectacled physician from Egypt, al-Qaeda has made subtle strategic shifts. He is seen as less preoccupied than bin Laden with mounting large-scale attacks against the United States, instead emphasizing regional struggles at a time when that message is more likely to resonate with Muslims in the Middle East.

By necessity, Zawahiri has narrowed al-Qaeda’s short-term ambitions. Unable to point to a sequel to the Sept. 11 attacks, Zawahiri has sought to find victories in the course of world events.

In his taped messages, Zawahiri has depicted the pending U.S. withdrawal from Afghanistan, budget cuts for the Defense Department and even the Arab Spring as evidence of America’s “shrinking and retreat.”

“He’s trying to jump on the bandwagon,” said Bruce Riedel, a former CIA analyst and terrorism expert at the Brookings Institution. Zawahiri has “gotten the endorsements of the entire global al-Qaeda empire,” Riedel said, but he presides over a core that has been “staggered and set back.”

As a result, U.S. counterterrorism officials are increasingly focused on a roster of regional affiliates. “Those groups, in total, will surpass the core al-Qaeda remaining in Pakistan,” Cardillo said.

Several have showed renewed strength over the past year.

The network’s once-dormant franchise in Iraq has carried out a string of deadly attacks across the country. It has also reversed smuggling routes that used to bring fighters and weapons in through Syria but are now being used to export violence to the uprising against that country’s president, Bashar al-Assad.

In North Africa, al-Qaeda’s franchise has made millions of dollars through kidnappings and other criminal enterprises, U.S. officials said, and is now using the money to stock up on weapons that have flowed out of Libya after dictator Moammar Gaddafi was overthrown.

Still, it is al-Qaeda’s affiliate in Yemen that “we’re most worried about, the affiliate we spend the most time on,” said the senior U.S. counterterrorism official. “They’re operating in the midst of essentially an insurgency, a multi-polar struggle for the control of Yemen. And that allows them the opportunity to recruit, to fundraise, to plot.”

Al-Qaeda in the Arabian Peninsula, or AQAP, as the Yemen-based group is known, has fused itself with a regional insurgency that has seized large portions of the country’s southern provinces over the past year.

The United States has responded by escalating a covert campaign of airstrikes by the CIA and the U.S. military’s Joint Special Operations Command. Earlier this month, Obama gave the agency and JSOC expanded authority to conduct strikes against targets that appear to be part of AQAP, even if the identities of those who could be killed is unknown.

AQAP is tied to the most recent major attacks on U.S. targets, including the mailing of parcels packed with explosives to addresses in Chicago in 2010, as well as the failed attempt to blow up a Detroit-bound airliner on Christmas Day in 2009.

AQAP has devoted more of its recent energies to regional ambitions — a shift that U.S. counterterrorism officials attribute to opportunism as well as bin Laden’s death.

“It doesn’t mean they’ve abandoned their global jihadist intentions,” the U.S. counterterrorism official said. “But they are more focused on their local situation partly so they can free up time and space, so that in the future they can take up the mantle again of the global jihad.”