The Death of Al Qaeda’s No. 2: The ‘Charismatic,’ Deadly Nasir al-Wahishi

— -- With the White House confirmation of his death, Nasir al-Wahishi has now become the biggest al Qaeda target to fall to the U.S. since Navy SEALs killed Osama bin Laden in May 2011 – not for just who the terror leader was before his death, but what he could’ve become.

Overnight al-Wahishi’s group, al Qaeda in the Arabian Peninsula, announced their leader’s death in a video uploaded online, saying the “hero of your heroes and master of your masters” was felled in an American drone strike in recent days. Hours later the White House National Security Council said the U.S. intelligence community “has concluded” the rumors are true and that al-Wahishi is dead – though the NSC didn’t say how al-Wahishi was killed. Later a U.S. official said a CIA drone strike was responsible.

Al-Wahishi kept a relatively low profile, despite being the leader of al Qaeda’s most dangerous affiliate. His name is not widely known outside of counter-terrorism professionals and observers.

But the man who was once bin Laden’s personal secretary was seen by analysts to have risen quickly through the terrorism ranks and was thought to be al Qaeda’s “leader-in-waiting,” according to a spy, one of the few Westerners that ever met the man.

Evolution of a Terror Apprentice

Al-Wahishi was born in Yemen in 1976 but left his home country for Afghanistan in the late 1990s, according to the Combating Terrorism Center at West Point. There he joined al Qaeda and bin Laden named him his personal secretary.

“For the next four years the two were nearly inseparable” and al-Wahishi watched al Qaeda’s founder as he constructed his terrorist organization, the CTC writes.

Al-Wahishi finally was separated from bin Laden in late 2001 in the chaos after 9/11 and, after being held for nearly two years in Iran, he was sent back to a Yemeni prison. But he and nearly two dozen others broke out of prison in 2006 and shortly thereafter, CTC said al-Wahishi “set about rebuilding” al Qaeda’s network in Yemen.

In 2009, al-Wahishi oversaw a merger between two local al Qaeda groups that created AQAP. Since, he has served as its leader, dodging drone strikes and ordering deadly attacks for years.

“When he left al Qaeda central, al-Wahishi built the franchise AQAP into the strongest part of the al Qaeda network and the arm that most directly threatened U.S.,” said Richard Clarke, former White House counter-terrorism advisor and ABC News consultant.

AQAP, along with its master bomb maker Ibrahim al-Asiri, is suspected of being responsible for a series of close-call bomb plots that targeted the U.S., including the botched 2009 Christmas Day bombing of an airplane in Detroit.

Though the attacks were not successful, al-Wahishi gained notoriety among al Qaeda’s members and followers.

In 2010 the U.S. designated al-Wahishi a terrorist, saying that “as AQAP’s leader, al-Wahishi is responsible for approving targets, recruiting new members, allocating resources to training and attack planning, and tasking others to carry out attacks.” Years later, the U.S. government put up a $10 million reward for information leading to his capture.

The Double Agent and the Heir to the Terror Throne

Morten Storm, a large, colorful Dane who says he went undercover to spy on al Qaeda for the U.S., British and Danish governments in the early 2010s, recounts in his book how he met al-Wahishi face-to-face in Yemen in 2012.

Storm was working for the Danish government at the time, pretending to be an al Qaeda supporter in order to get close to the group’s top leadership. He had already ingratiated himself with AQAP after befriending U.S. citizen-turned-al Qaeda cleric Anwar al-Awlaki, who had been killed several months before in a CIA drone strike.

“The car stopped and a new passenger slid in next to me. I looked up and saw the unmistakable features of Nasir al-Wuhayshi – wispy beard, small, close-set eyes under his tribal scarf, and his trademark broad grin,” Storm writes in “Agent Storm,” using an alternate spelling for al-Wahishi.

The two spent hours together in Yemen’s backcountry that day, discussing Awlaki’s death and potential future operations. Al-Wahishi tried to convince Storm that there were no such things as “civilians” when it came to non-believers, but also said that he would rather only strike military targets. In short time, Morten said he was “fascinated by Wuhayshi.”

“He had the same soft spoken humility as his mentor, [Osama] bin Laden, and exuded the same charisma. His fighters loved him and would do anything for him. No wonder people saw him as the leader-in-waiting of all al Qaeda,” Storm writes.

Just a year after Storm met with al-Wahishi, the AQAP leader was officially named deputy to Ayman al-Zawahiri, the leader of overall al Qaeda since bin Laden’s death, according to the State Department.

Analysts widely believed that if Zawahiri was killed, or if he abdicated his throne, al-Wahishi would be the logical next choice to lead overall al Qaeda.

In mid-2014, al-Wahishi seemed to almost taunt the U.S. military and intelligence by appearing in the open in a propaganda video amid dozens of followers – an event one U.S. official said was “atypical” of security-conscious al Qaeda leaders.

“The enemy crusader still has cards to play,” al-Wahishi says in the video. “We must remember that we are always fighting against the big enemy. We must eliminate the cross held by the cross-bearer, America.”

Days after the video, the U.S. unleashed a barrage of missiles aimed at terror targets in Yemen, but until now, no U.S. strikes managed to find al-Wahishi.

Bruce Riedel, a 30-year veteran of the CIA and current Director of the Intelligence Project at Brookings, said that had al-Wahishi taken over al Qaeda, it could have led to a revitalization of the terror group and one that focused more on recruiting and fighting in Yemen and Syria. In Syria, al Qaeda’s second-most deadly franchise, al Nusra Front, is battling the al Qaeda breakaway group ISIS.

“I don’t think it’s good to underestimate Zawahiri. His track record is pretty impressive,” Riedel told ABC News. “But he is an old man, and terrorism is not really an old man’s business. Younger leadership would’ve helped al Qaeda at this point. Al-Wahishi would’ve provided that.”

Matt Olsen, former Director of the National Counterterrorism Center and an ABC News consultant, said that removing al-Wahishi, who he called an “effective and determined leader,” from the playing “leaves al Qaeda leadership in Pakistan with few capable leaders to turn to.”

Still Riedel said that by killing al-Wahishi, the U.S. is far from destroying the threat from al Qaeda as a whole or AQAP.

“It’s a welcome development, but the strategy of decapitating al Qaeda franchises is a proven failure,” he said. “It’s not that is isn’t a useful thing to do, but it isn’t sufficient.”

ABC News’ James Gordon Meek and Luis Martinez contributed to this report.