Who was Al-Zawahri and why did US kill him?

FILE - In this television image from Arab satellite station Al-Jazeera, Osama bin Laden, right, listens as his top deputy Ayman al-Zawahri speaks at an undisclosed location, in this image made from an undated videotape broadcast by the station April 15, 2002. [AP]

A U.S. drone strike in Afghanistan this weekend killed Ayman al-Zawahri, who helped Osama bin Laden plot the September 11, 2001, attacks on the United States and helped al-Qaida survive and spread in the years after. By finding and striking al-Zawahiri, President Joe Biden said, the U.S. was ensuring that Afghanistan under the Taliban would never again become a base for attacks on the rest of the world, as it was in 2001.

A look at the al-Qaida leader, who evaded U.S. capture for 21 years after the suicide airliner attacks that in many ways changed America and its relations with the rest of the world.