What Is AQAP, the Terror Group Holding American Captive?

Late Wednesday an affiliate of al Qaeda released a harrowing video showing a British-born American hostage who they say will be killed in three days if President Obama doesn't meet the terror group's demands.

Americans have sadly become familiar with their countrymen appearing in hostage videos halfway around the world - the terror group ISIS separately filmed three American civilians they held in Syria before executing them in recent months - but this time it was the Yemen-based al Qaeda in the Arabian Peninsula (AQAP), not ISIS, forcing U.S. citizen Luke Somers to plead for his life.

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And while ISIS has come to dominate headlines since cutting a brutal swath through Syria and Iraq in recent months, it's AQAP that top U.S. security officials have said presents the greatest external terror threat to the homeland - the same group behind sophisticated and narrowly-foiled airline bomb plots, and the group led by the man who may one day take over as leader of all of al Qaeda.

So what is AQAP?

Out of Yemen, Target: America

Al Qaeda in the Arabian Peninsula (AQAP) was formed in 2009 after a Yemeni faction of al Qaeda and Saudi extremists agreed to pool their terrorism talents and resources, according to the U.S. National Counterterrorism Center. The group, which declared its allegiance to al Qaeda "core" leader Osama bin Laden before his May 2011 death, started with local operations, but soon turned its attention to a "global strategy," including several direct attempts to attack America.

The same year as AQAP's founding, the terror group launched a nearly-successful operation to bomb an American airliner in Detroit. The Christmas Day 2009 attack only failed because the explosive device hidden inside the underwear of then-23-year-old Umar Farouk Abdulmutallab ignited, but failed to detonate.

"It's very clear it came very, very close," former Rep. Pete Hoekstra, R-Mich. and then-ranking member of the House Intelligence Committee, said at the time.

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U.S. officials said AQAP followed that attempt up with another the next year, in which explosive-laden packages were meant to be sent by cargo planes to the U.S. and then detonated. That attack was foiled after the packages were intercepted in Dubai and England, thanks to a tip from Saudi intelligence.

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In May 2012, reports emerged that a double agent, working with allied intelligence agencies and the CIA, had infiltrated AQAP posing as a suicide bomber and made off with an explosive device he was supposed to take on yet another U.S.-bound aircraft.

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Who's Cooking Up All These Plots?

AQAP is believed to be led by the wiry Nasir al-Wahishi, who the U.S. State Department says is "responsible for approving targets, recruiting new members, allocating resources to training and attack planning, and tasking others to carry out attacks." The U.S. offers a $10 million reward for information leading to his capture.

Al-Wahishi has survived in the dangerous position as AQAP's commander since 2009 and just earlier this year seemed to poke a finger in the eye of U.S. intelligence by appearing in a video in the open before a large gathering of AQAP fighters.

"We must eliminate the cross held by the cross bearer America," he told his followers.

The video appearance was answered days later with a barrage of airstrikes, which Yemeni officials said killed dozens of suspected AQAP members and a small number of civilians.

Al-Wahishi apparently survived, and U.S. counter-terrorism officials have told ABC News he could be the one to take on the mantle of leader of al Qaeda "core" in Pakistan following Ayman al-Zawahiri.

But while al-Wahishi is at the top of AQAP's command structure, U.S. security officials are equally, if not more concerned, about Ibrahim al-Asiri, identified as the terror group's master bomb maker.

Al-Asiri is believed to have been the mastermind behind the airline bombing attempts on the U.S., as well as a particularly gruesome failed attempt on a member of the Saudi royal family in 2009. In that case, al-Asiri supposedly hid explosives in the rectum of his younger brother, who then attempted to detonate the device while in the presence of Saudi Prince Muhammed bin Nayif.

The explosion was apparently underpowered and only managed to kill al-Asiri's brother, but as the State Department put it, "the brutality, novelty and sophistication of the plot is illustrative of the threat posed by al-Asiri." The U.S. offers $5 million for information leading to al-Asiri's capture.

Recently Western officials have said they are also worried about his protgs, including at least one Westerner, who are believed to have learned al-Asiri's twisted techniques.

High-Profile American AQAP Members, Killed in Drone Strike

But better known in AQAP than al-Wahishi or al-Asiri, at least in American security circles, was Anwar al-Awlaki, an American citizen and a high-profile recruiter for the organization.

Born in New Mexico and educated in Colorado, al-Awlaki's radical English-language sermons posted online propelled him to star status in jihadi circles. While living in America, Awlaki met with two future 9/11 hijackers and later, while living in Yemen, corresponded with Nidal Hasan, the U.S. Army major convicted of killing 13 people when he opened fire at the Army's Fort Hood base in Texas in 2009.

President Obama authorized the military and U.S. to kill al-Awlaki in early 2010. Later the government said al-Awlaki also served as AQAP's chief of external operations.

Al-Awlaki responded to his name being added to the kill list with internet messages taunting President Obama and releasing a video in which he said jihadis do not have to ask permission to kill Americans.

"Fighting the devil doesn't require consultation or prayers seeking diving guidance," he said then. "They are the party of the devils."

Anwar Al-Awlaki: From American Boy to Face of Terror

Awlaki was killed in a CIA drone strike in September 2011 - the only American known to have been targeted in a strike under the Obama administration. Another American, however, was killed by coincidence in the same strike - AQAP member Samir Khan, the editor of an English-language AQAP propaganda magazine.

A third American, al-Awlaki's 16-year-old son Abdulrahman, was killed in a separate drone strike in Yemen days later that the U.S. said targeted another militant nearby.

How Is AQAP Related to ISIS?

In the shadowy world of global terror, it's often hard to see who is on who's side and the case of AQAP and ISIS is no different. ISIS used to be an al Qaeda affiliate itself, but its leader, Abu Bakr al-Baghdadi, had a public, divisive falling out with al Qaeda leader Ayman al-Zawahiri.

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Since, various al Qaeda affiliates have expressed varying levels of support or condemnation for ISIS. AQAP reportedly put out a statement in support of ISIS in August, but then in November, some of the group's top clerics publicly rebuked al-Baghdadi and ISIS's declaration of an Islamic caliphate.

It remains to be seen how AQAP will deal with Luke Somers. Another al Qaeda affiliate, the al-Nusra Front in Syria, released an American it was holding in August. ISIS, on the other hand, has killed every Western hostage it has shown on camera.

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Contact the author at lee.h.ferran@abc.com