Ayman al-Zawahiri has become the world's most wanted man after al-Qa'ida announced that the Egyptian-born surgeon succeeded Osama bin Laden to head the global terror organisation six weeks after the Saudi leader's slaying in Pakistan.
"The general command of al-Qa'ida, after completing consultations, decided that the sheikh doctor Abu Mohammed Ayman al-Zawahiri take the responsibility and be in charge of the group," said a statement, purportedly issued by al-Qa'ida and posted on several jihadist websites.
Long-serving as Bin Laden's deputy, the al-Qa'ida co-founder has effectively served as the operational head of the terror group for at least the past six years. But there are doubts about whether Zawahiri will be able to maintain the terror syndicate's cohesion, or watch it will fracture into smaller, localised groups in the absence of Bin Laden's symbolic leadership.
There were early signs of support from one of the most dangerous al-Qa'ida affiliates yesterday as the Pakistani Taliban backed the succession. "We share the same path with al-Qa'ida," said Pakistani Taliban spokesman Ahsanullah Ahsan. "We are allies." Pakistan is reeling from a series of deadly "revenge" attacks since the raid that killed Bin Laden.
But it remains to be seen if Zawahiri can exert similar sway over other branches of the terror franchise in the Arab world. Marginalised by the Arab Spring, which has dealt a severe blow to al-Qa'ida's attempts to rally public support behind their murderous methods as a means of toppling dictators, the terror group faces a crisis of relevance.
Beyond Pakistan, the terror group has affiliates in the Arab Peninsula and North Africa. These groups are seen by experts to be exercising greater autonomy, and it is unlikely that Gulf jihadists will defer to a wizened and fractious Egyptian jihadist, who has none of his Saudi predecessor's mystique.
At the White House yesterday, officials suggested they were not intimidated by the news of Zawahiri's ascent to the top post at al-Qa'ida, in part because of his lack of charisma and leadership qualifications. President Barack Obama's counter-terrorism advisor, John Brennan, said after Bin Laden's death that Zawahiri had a lot of detractors within al-Qa'ida because he wasn't involved earlier in the fight in Afghanistan.
Fearless, self-righteous, and convinced of the truth of his own beliefs is how the Pulitzer prize-winning writer Lawrence Wright described Zawahiri. These enduring headstrong qualities, he writes in The Looming Tower, "put him in conflict with nearly everyone he would meet".
For Zawahiri, however, staying alive will likely prove his biggest challenge. After evading capture for over a decade, the US has intensified its manhunt, buoyed by the intelligence it has harvested from Bin Laden's compound.
In a sign that he is suspected to be hiding in Pakistan, Hillary Clinton urged the country's leaders to join the US in a combined effort to track him and four other militant leaders on a visit to Islamabad last month. Another name on the list, Ilyas Kashmiri, was reportedly struck down in a drone attack in South Waziristan earlier this month.
A familiar face from the chilling video threats he has issued in recent years, Zawahiri's last known locations are in Pakistan. In January 2006, he fled a hideout in the Bajaur tribal agency town of Damadola before a missile struck. Given the intensity of the current drone effort, many suspect that he may have located to one of Pakistan's cities, where Bin Laden and other al-Qa'ida leaders have been found.
Now nearly 60, Zawahiri first arrived in Pakistan in 1980 to work in relief camps for Afghan refugees. He came from a family of medical professionals, distinguished religious scholars and politicians. Zawahiri's grandfather was Egypt's ambassador to Pakistan.
Inspired by the hardline Egyptian ideologue Sayyid Qutb, Zawahiri was only 15 when he helped form an underground Islamist cell intent on overthrowing the Cairo government and establishing an Islamist state. He was later imprisoned for three years in the aftermath of the assassination of Egyptian President Anwar Sadat. In the earliest of his television appearances, a young Zawahiri addresses cameras through the bars of a cell. "We tried our best to establish this Islamic state and the Islamic society," he shouts animatedly.
Q&A: The obvious choice – what took so long?
Was this announcement a surprise?
No. Ayman al-Zawahiri has been al-Qa'ida's number two for more than a decade. He has been at the heart of its every tactical and philosophical change.
Why did it take so long?
That's the one perplexing thing about al-Qa'ida's statement. The core leadership are known to replace leaders very quickly. Some security experts have speculated that the delay may have been caused by infighting.
Where is he?
Most analysts would have said somewhere in Pakistan's tribal areas along the Afghan border. But following Bin Laden's death in Abbottabad, about 40 miles from Islamabad, the US may have to cast a wider net.
Is he a popular figure?
Amongst the most extreme militants, Bin Laden was revered as a charismatic billionaire who gave up a life of luxury to fight jihad. Zawahiri, meanwhile, is notoriously fractious character and has a history of falling out with key militants. He is known to be haughty and an Egyptian supremacist, something which particularly riles Gulf Arab fighters.
What will happen to al-Qa'ida now?
Unless Zawahiri is killed or captured and replaced by a younger generation of leaders, it is likely al-Qa'ida will follow a similar path. A key task for the new leadership will be to make violent Islamist militancy relevant at a time when the Arab Spring has caught militants off guard.