Profile: Abu Yahya al-Libi
Abu Yahya al-Libi, said by the White House says to have been killed in a drone strike on north-western Pakistan, is described by US officials as the "general manager" of al-Qaeda.
They say the 49-year-old Libyan was second-in-command to Ayman al-Zawahiri, who was named al-Qaeda leader after Osama Bin Laden's death last year.
Libi, also known as Hasan Qayid, and Yunis al-Sahrawi, is thought to have been a member of the Libyan Islamic Fighting Group before he allied himself to Osama Bin Laden.
Security experts say he was considered by the organisation to be a daring and inspirational figure - a convincing speaker with strong religious credentials.
He claimed to have been captured by Pakistani forces in 2002 and then sent to the US military airbase at Bagram in Afghanistan, from where he escaped in July 2005 along with three other al-Qaeda members.
Libi said the four had picked a lock and crept past their guards to freedom.
He then emerged as a heroic figure, and al-Qaeda's leading theologian. He became its most visible face on video, surpassing Ayman al-Zawahri in recent years.
In a 2009 profile of Libi in Foreign Policy magazine, terrorism expert Jarret Brachman described him as "masterful at justifying savage acts of terrorism with esoteric religious arguments".
Al-Qaeda named Libi as a field commander in Afghanistan, he subsequently styled himself in his many videos as a theological scholar, and spoke on a variety of global issues of importance to the group.
Libi is believed to have gone to Afghanistan in the early 1990s before being sent to study Islam in Mauritania.
On his return he toured al-Qaeda training camps in the country that was by then under the control of the Taliban.