But in the years since the killing of Osama bin Laden, the Islamic State in Iraq and the Levant's barbarity and relentless march across Iraq and Syria have stolen the spotlight.
So does al-Qaeda face a fight to stay relevant? And is the lure of ISIL to blame?

Presenter: David Foster
Guests:
Shiv Malik - investigative journalist with The Guardian newspaper
Aymenn Jawad Al-Tamimi - military specialist and fellow with the Middle East Forum
Robin Simcox - al-Qaeda specialist
Source: Al Jazeera