Thirteen months after Osama bin Laden was killed, the loss of charismatic propagandist Abu Yahya al-Libi is a crippling blow to Al-Qaeda that could break up its central leadership, US experts say.
Killed Monday in a CIA drone strike in Pakistan, Libi was considered to be number two in the hierarchy after bin Laden's successor, Ayman al-Zawahiri, but experts say his influence outweighs simplistic numeric distinctions.
Beloved of rank-and-file jihadists, he held the religious credentials that other leaders lacked and served an invaluable role as an inspirational propagandist who kept the global terror network unified and on message.
"The death of Abu Yahya al-Libi is a devastating blow to Al-Qaeda's senior leadership, probably unrecoverable," terrorism expert Jarret Brachman of North Dakota State University said.
"Nobody remaining in Al-Qaeda has his combination of scholarly credentials, personal charisma, and the ability to steer and guide Al-Qaeda's regional affiliates and broader global movement."
Zawahiri, a 60-year-old Egyptian former surgeon, is credited with great organizational skill and cunning, but he lacks bin Laden's potent charisma, and now his younger 49-year-old deputy -- a man who was in many ways his perfect foil -- is also gone.
"Not only was Libi revered, but he was loved by Al-Qaeda's followers," said Brachman. "Abu Yahya not only illuminated the path for Al-Qaeda but in many ways helped to blaze the ideological trail on which the global movement would follow."
On escaping US custody at Bagram air base in Afghanistan in 2005, the little know Libyan preacher who studied Islam in Mauritania prior to the September 11 attacks became an overnight star in jihadist circles.
Bin Laden charged him with consolidating Al-Qaeda's message through the terror network's media arm As-Sahab, and Libi went about ensuring that the next generation of jihadists didn't stray far from their leader's wishes.
"Without him to herd the wandering cats of Al-Qaeda, the movement is likely to begin to drift," Brachman said, speculating that another strike could end central Al-Qaeda as we know it.
"This is one of two very important remaining nails in Al-Qaeda core's coffin," he said.
"If Zawahiri is put down soon, Al-Qaeda's senior leadership will be broken and the torch will have to pass to AQAP," he said, referring to Al-Qaeda in the Arabian Peninsula, which is based in Yemen and considered Al-Qaeda's most active regional franchise.
US President Barack Obama's administration trumpeted the death of a man who had appeared in countless Al-Qaeda videos and was considered the chief architect of its global propaganda machine.
"Zawahiri will be hard-pressed to find any one person who can readily step into Abu Yahya's shoes," one US official said.
"In addition to his gravitas as a longstanding member of Al-Qaeda's leadership, Abu Yahya's religious credentials gave him the authority to issue fatwas, operational approvals, and guidance to the core group in Pakistan and regional affiliates.
"There is no one who even comes close in terms of replacing the expertise Al-Qaeda has just lost."
Al-Qaeda's line of succession is unclear, but for US terrorism expert Bill Braniff, the number attached to Libi is unimportant compared to his value as a highly-visible propagandist.
"It is easier for Al-Qaeda to find someone who can conduct an operational mission and much harder for them to find someone who can credibly serve as a voice, a mouthpiece," he said.
"You need someone who everyone can turn to and look at and listen to."
Braniff said the documents retrieved by US commandos from bin Laden's Abbottabad lair in Pakistan during the raid that killed him in May last year laid bare the importance of Libi's role as a "generational bridge" who could glue together Al-Qaeda's geographically disparate parts.
"His loss exacerbates a leadership problem for an organization that had already lost its ability to shape the violence of associated organizations, evidenced in the bin Laden documents," the expert said.
"For As-Sahab media, the only remaining center of gravity for Al-Qaeda core, the loss of their most charismatic figure may be devastating. It was through As-Sahab media featuring Al-Libi that Al-Qaeda core managed to convey the image of an ideologically and militarily competent outfit."