Al-Qaeda in the Arabian Peninsula
Al-Qaeda in the Arabian Peninsula (APAP) was formed from the merger of Saudi and Yemeni groups, and is the main group attempting terrorism against the U.S. and Saudi Arabia, especially recent attempted airliner bombings.
It is believed to be headed by Nasser al-Wahishi, a Yemeni who escaped from a prison in Sanaa in 2006. This is a newer "affiliate" than the others, and seems to have learned from the other al-Qaeda affilliates. Anwar al-Awlaki is a prominent member, involved with promoting self-radicalization.
The Republic of Yemen has an unusual mix of tribal and central government.
As opposed, in particular, to al-Qaeda operations in Afghanistan, Iraq, Saudi Arabia and Sudan, the group is largely "home-grown" and cooperates much more effectively with existing tribal structures. "They've worked hard to put deep, and what they hope are lasting, roots that will make it very difficult for them to be rooted out of Yemen," says Gregory Johnsen, a Yemen expert at Princeton University. "They've done a good job of looking at the mistakes that other versions of al Qaeda have made elsewhere."
"As long as Qaeda respects the tribes, some tribes will welcome them," says Sheikh Abdulqawi Sherif, the head of the pro-government Bani Dhabian tribe, whose land borders Mareb and Shebwa provinces, two areas where al Qaeda cells are based. Gen. Yahya Saleh, nephew of Yemen's president and the head of one of the country's counterterrorism forces, acknowledges the alliances some tribes have with al Qaeda.
Still, he says, "the tribes in Yemen are practical. They know there will be a heavy price to pay for harboring al Qaeda, and more and more, [the tribes] will not be willing to pay that price."
Most recently, it was associated with package bombs sent by air courier service to the U.S. 
It had been operating locally, as with a suicide bombing against Korean tourists in March 2009, , but it appears responsible for the attempted suicide bombing of a U.S. aircraft on 25 December 2009.
The Saudi elements escaped to Yemen after intensified security in 2004 and 2005. In February 2006, 23 Yemeni prisoners escaped from the main prison in the Yemeni capital, Sanaa. Two of those escaped prisoners – Nasser al-Wahishi (or Wuhaishi) and Qasim Al Raimi – now head AQAP, although Saeed al-Saudi Shahrani has also been described as al-Wahishi's deputy. "Two former Guantanamo Bay detainees, and graduates of the Saudi rehabilitation program, appeared in a video announcing the merger and assumed senior positions (although one later left and surrendered to Saudi authorities). The group went public just days after U.S. President Barack Obama's inauguration and vow to shut Guantanamo."
- Peter Finn, Greg Miller and Anne E. Kornblut (30 October 2010), "Intercepted packages could have exploded anytime, British officials say", Washington Post
- Charles Levinson and Margaret Coker (22 January 2010), "Al Qaeda's Deep Tribal Ties Make Yemen a Terror Hub", Wall Street Journal
- "Qaeda suicide bomber behind Yemen tourist attack", Reuters, 16 March 2009
- Al-Qaeda in the Arabian Peninsula, Al Jazeera, 29 December 2009
- Michelle Shephard (2 January 2010), "Yemen: Terror threat? U.S. ally? Nearly failed state?", The Star (Canada)