Channel 4 News looks at the al-Qaeda group in the Arabian Peninsula linked to explosives found on two cargo planes, and Public Enemy No 1 for the UK intelligence services, Anwar al-Awlaki.
The Leader of al-Qaeda in Yemen, Nasser al-Wahaishi (2nd R), his deputy Said al-Shihri (2nd L), the group's field commander, Mohammed al-Oufi (R) and the group's commander, Qassim al-Raimi (L) appear in a rare video posted on the Internet on 24 January 2009.
Al-Qaeda in the Arabian Peninsula (AQAP) was formed in January 2009 in a merger between two regional strands of the terror group in Saudi Arabia and Yemen - Osama Bin Laden's ancestral home.
The group is led by a former aide to Bin Laden, Nasser Abdul Karim al-Wuhayshi, and was singled out by President Obama as planning "attacks against our homeland, our citizens, and our friends and allies". It is believed to have several hundred members, including preacher Anwar al-Awlaki, who was allegedly a mentor for some of the 9/11 attackers.
The most recent example of AQAP's threat was an underwear bomb seized by authorities in the Middle East, which the US believes was intended to give to a suicide bomber to blow up an airliner bound for the US or another Western country.
US officials said the aborted plot shows AQAP remains intent on attacking the United States or its allies, and is continuing to evolve its weapons and tactics. One source said the bomb is similar to the work of bomb-maker Ibrahim Hassan Al-Asari, who is believed to be working with the militant group.
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Al-Awlaki, who has lived in both the US and Britain, was singled out by MI6 chief Sir John Sawers in his first public speech this week, describing him as al-Qaeda's leader. "From his remote base in Yemen, al-Qaeda leader and US national Anwar al-Awlaki, broadcasts propaganda and terrorist instruction in fluent English, over the internet," he said.
And in September, MI5 Director General Jonathan Evans said he was of "particular concern" to the West.
"His influence is all the wider because he preaches and teaches in the English language which makes his message easier to access and understand for Western audiences," he said.
"We saw his hand in the Abdulmutallab case. There is a real risk that one of his adherents will respond to his urging to violence and mount an attack in the UK, possibly acting alone and with little formal training, and we have seen a surge in Yemen related casework this year."
AQAP has vowed to attack foreigners and security forces as part of an effort to topple the Saudi and Yemeni governments, and establish an Islamic state. It has claimed responsibility for a number of attacks in the two countries over the last 12 months.
"His influence is all the wider because he preaches and teaches in the English language"
MI5 Director General Jonathan Evans on Preacher Anwar al-Awlaki
Al-Qaeda's Coming Home
The inspiration for this attack may have come from Anwar al-Awlaki, the radical American cleric of Yemeni descent hiding somewhere in Yemen. He is believed to have inspired Abdulmutallab's Detroit exploit as well as the massacre at Fort Hood in Texas which left 13 people dead. Awlaki was the only wanted terror suspect named by Sir John Sawers, the MI6 Chief, in his first very prescient public speech last Thursday. Sawers is an Arabist and knows Yemen - he served there as a junior intelligence officer at the beginning of his career, so his appointment as the new "C" last November has turned out to be prescient too.
For it seems inevitable that the focus of western intelligence agencies will have to widen and shift from the Pakistan-Afghanistan border back to the Arabian Peninsula, where al-Qaeda began. Osama Bin Laden, a Saudi of Yemeni descent, almost certainly had nothing to do with this plot. If he later applauds it in an audio tape smuggled out of the Pakistan border region, it may be to claim credit for an act of terror he can no longer order or control.
Osama Bin Laden remains al-Qaeda's figurehead. But Anwar Al-Awlaki could now be the evil brains behind the Arabian franchise of al-Qaeda - the franchise which the Arab world and the West have to fear most. I don't believe the date of this would-be attack was coincidental. Al-Qaeda likes big diary days. It tried to attack last Christmas. The ghosts and ghouls of Halloween must have been tempting.
AQAP was also blamed for the Christmas Day bomb plot in the US. Umar Farouk Abdulmutallab, the former London-based student charged in relation to that plot, allegedly told investigators that AQAP operatives trained him in Yemen, equipped him with a powerful explosive device and organised his mission.
In 2006, 23 suspected al-Qaeda members escaped from prison in Yemen's capital, Sana'a. Most were recaptured, but former Bin Laden aide Nasser Abdul Karim al-Wuhayshi got away. He is said to have overseen the rebuilding of al-Qaeda in Yemen and announced the creation of "al-Qaeda of Jihad Organisation in the Arabian Peninsula" in January 2009.
Previous incarnations of the group are also believed to have been behind attacks on foreign compounds in Saudi Arabia. Extremists claimed responsibility for simultaneous suicide bombing attacks in May 2003 on three Western housing compounds in Riyadh, which left 29 dead. Another attack on the Muhayyah residential compound in the capital in November that year killed 17 people.
Al-Qaeda activists migrated to Yemen over the next few years as militants took advantage of the weak central government and anti-western sentiment in the country.
In AQAP's official Arabic-language magazine in February this year, they included an article on the device used in the Christmas Day foiled plot.
"The article provides insights into how the group approaches IED design and creates devices for specific targets and operations," says IntelCentre. "The creation of devices built into toner cartridges fits within this philosophy and would not be surprising to see coming out of AQAP. If this attack is by AQAP, it demonstrates an accelerated ability to design new and innovative ways of conducting IED attacks and a focused effort to execute those attacks on US soil."
In the article the group says: "The tight security inside the office of a security official under observation and guard is totally different than an airplane that is in the air for six hours. It is certain that the conditions in the later situation will be more flexible and do not raise suspicions during implementation."