Why killing of al Qaeda's Ayman al-Zawahri is important in fight against terror

After years of quietly assembling the suicide attackers, funds and plans for the Sept. 11 attack, al Qaeda leader Ayman al-Zawahri and lieutenants ensured that al-Qaeda survived the global manhunt that followed to attack again.

On the run after 9/11, al-Zawahri rebuilt al-Qaeda leadership in the Afghan-Pakistan border region and was the supreme leader over branches in Iraq, Asia, Yemen and beyond.

With a credo of targeting near and far enemies, al-Qaeda after 9/11 carried out years of unrelenting attacks: in Bali, Mombasa, Riyadh, Jakarta, Istanbul, Madrid, London and beyond.

Attacks that killed 52 people in London in 2005 were among al-Qaeda's last devastating attacks in the West, as drone strikes, counterterror raids and missiles launched by the U.S. and others killed al-Qaeda-affiliated fighters and shattered parts of the network.

Also watch: Biden: killing of al-Qaida leader Ayman al-Zawahri is long-sought 'justice'