Nine years after 3,000 people died in the 9/11 attacks, Al-Qaeda, the group behind the carnage, has taken many hits but remains a formidable threat, operating from Pakistan and through support groups, experts and officials say.
The network created by Osama bin Laden in 1988 no longer seems able to carry out complex attacks such as those that destroyed the World Trade Center and damaged the Pentagon, but their masterminds are alive and at large.
This fact is being celebrated as a clear victory by the terror group and its supporters.
"Counterterrorism efforts against Al-Qaeda have put the organization in one of its most difficult positions since... late 2001," Dennis Blair said early this year when he was Director of National Intelligence, a US cabinet-level official.
"However, while these efforts have slowed the pace of anti-US planning and hindered progress on new external operations, they have not been sufficient to stop them."
Blair added: "Until counterterrorism pressure on Al-Qaeda places of refuge, key lieutenants and operative cadres outpaces the group's ability to recover, Al-Qaeda will retain its capability to mount an attack."
Pressure is above all applied through missiles fired by US drones which have hit Al-Qaeda and Pakistani insurgents' "safe houses" in tribal areas near the Afghan border about 100 times since August 2008.
The strikes have killed about 1,000 rebels including many of Al-Qaeda's operating officers.
"The network is focused on its own survival, which is closely linked with the future of its jihadist allies in Pakistan," said Jean-Pierre Filiu, professor at Sciences Po, an elite school in Paris, and author of "Les Neuf vies d'Al-Qaïda" (The Nine Lives of Al-Qaeda).
"Al Qaeda-Central has become more and more Pakistani and is practically absent from Afghanistan," said Filiu.
"This is based on something that has been acknowledged by everyone -- that there is a special relationship between the Pakistani government and (the powerful insurgent network) Haqqani which protects bin Laden."
Haqqani network leaders are based in Pakistan's mountainous North Waziristan region. Created by Afghan warlord Jalaluddin Haqqani and run by his son Sirajuddin, the group is one of the toughest foes for foreign forces in Afghanistan, particularly in the east of the country.