It has now been two years since U.S. Navy SEALs dropped into a dark compound in Abbotabad, Pakistan, and killed Osama bin Laden. It was an event that stopped the nation in its tracks and was seen as a turning point in America's fight to stop al Qaeda's terror network.
In those two years the al Qaeda terror network has become so decentralized that its affiliates in Yemen and elsewhere now pose a greater direct threat to the U.S. Though weakened, counterterrorism analysts believe al Qaeda will continue to inspire potential Islamic extremists for years to come.
The raid was seen as a turning point in the war on terror and provided a "treasure trove" of documents that revealed the surprising degree of operational control bin Laden still had over the terror network.
The details of the bin Laden raid have since been portrayed in the movie "Zero Dark Thirty" and in a book written by one of the Navy SEALs involved in the mission to kill the world's most wanted man.
Bin Laden's death was undoubtedly a severe blow to al Qaeda, but counterterrorism analysts continue to see the group as a potential threat to the U.S., though its role has evolved.
"The threat from Al Qaeda and the potential for a massive coordinated attack on the United States may be diminished, but the jihadist movement is more diffuse," James Clapper, the Director of National Intelligence (DNI) told Congress in April. "Lone wolves, domestic extremists and jihad-inspired affiliated groups are still determined to attack Western interests."
Read More: ABC's Full Coverage on the raid and death of Osama bin Laden.
Surprisingly, the terror threat posed by al Qaeda and other terror groups did not top this year's version of the Worldwide Threat Assessment prepared by the DNI. It was the first time since the Sept. 11, 2001 terrorist attacks that the terror threat was not ranked as the number one threat to U.S. national security.
"Senior personnel losses in 2012, amplifying losses and setbacks since 2008, have degraded core al Qaeda to a point that the group is probably unable to carry out complex, large-scale attacks in the West," said Clapper. Those losses have come from the CIA's controversial drone strike program in Pakistan's tribal areas where al Qaeda leaders are believed to continue to operate.
While "core al Qaeda" has been weakened, its affiliate in Yemen, al Qaeda in the Arabian Peninsula (AQAP), has pursued attacks on U.S. interests like the unsuccessful underwear bomber attack in 2009. A similar attack was thwarted last year around the time of the one year anniversary of bin Laden's death.
The threat posed by AQAP led to an expansion of the CIA's drone program into Yemen targeting the group's leaders including American born Islamic cleric Anwar al Awlaki.
Bruce Hoffman, a counterterrorism expert at Georgetown University, says bin Laden's death in May 2011 was regarded "as a decisive corner having been turned in the war on terror" and agrees that it hastened the terror network's decline. However, he is concerned by what he calls the "rise in al Qaedism" whose message of Islamic militancy targeting the U.S. has resonated in places like northern Africa where last September's deadly attack on the U.S. consulate in Benghazi was believed to have been carried out by al Qaeda supporters.
"We see the threat of its ideology to places where hitherto it really was not terribly strong or salient and we see almost a revival of its brand," says Hoffman. He adds that Islamic terrorists continue to cite al Qaeda as an influence and "aspire to emulate al Qaeda's ideology" of a violent struggle against the United States.
"I think the challenge of al Qaeda remains," says Hoffman. "We may want to wish it away, and we may want to believe that killing bin Laden killed off the brand, or killed off the ideology, but we don't see any evidence of that."
Brian Jenkins, with the Rand Corporation, agrees that bin Laden's death had "an immediate impact" on the group's morale and believes it became even more decentralized and dependent on its allies and affiliates since his death which could erode the group's ideological focus of a violent struggle against the United States.
"One of the things bin Laden did by his very existence was maintain a unanimity of focus, a degree of unity, a single-minded focus on its ideology," says Jenkins. While bin Laden's successor, Ayman al Zawahiri, has struggled to maintain that ideological focus Jenkins believes it could continue to erode and al Qaeda could fragment into many localized movements.
Jenkins is concerned that an "opportunistic" al Qaeda could be resurgent in Syria and Afghanistan. In Syria, Islamic extremists are playing a growing role in the fight to topple President Bashar al Assad leading to concerns about what a post-Assad Syria might look like. In Afghanistan, Jenkins is concerned that al Qaeda could once again find a safe haven in that country should the Taliban expand its control after U.S. combat forces pull out by the end of 2014.
"We have to presume this sort of thing will go on," said Jenkins. "All of these are opportunities for al Qaeda. It's not the same al Qaeda it was on Sept. 11. It's very different and it's still there, and I for one wouldn't exaggerate its death, but I'm not writing its epitaph right now."
Another possible indicator of al Qaeda's diminishing role is the decrease in the number of the CIA's drone strokes in Pakistan this year. Hoffman speculates the decrease could be the result of fewer al Qaeda targets or because "we don't have the intelligence to identify emergent al Qaeda leaders and single them out." He also thinks it might be possible that al Qaeda has gone underground in Pakistan's large cities.
Though credited with reducing core al Qaeda's operational capability, even some of the drone strike program's supporters are now expressing concern that it may be creating longer lasting negative effects that could undermine long term efforts to combat extremism.
"We're seeing that blowback," Gen. James Cartwright, the former vice chairman of the Joint Chiefs of Staff, said in March at the Chicago Council on Global Affairs. "If you're trying to kill your way to a solution, no matter how precise you are, you're going to upset people even if they're not targeted."
Last month, Cartwright said at the first ever Congressional hearing on the drone program that the U.S. risked losing "the moral high ground" if it did not reveal additional details about the program's legal basis and oversight.