By Tim Lister and Paul Cruickshank
Abu Sufyan Said al-Shihri was prisoner number 327 at the Guantanamo Bay, Cubla, detention center, transported there after being captured as he tried to cross the border into Pakistan from Afghanistan late in 2001.
But in 2007 he argued before a review board that he was a Muslim - not a terrorist - and if allowed to return home to Riyadh in Saudi Arabia he would join his family's furniture business.
Al-Shihri was repatriated and put through a rehabilitation program, but within months absconded to become one of the founding members of al Qaeda in the Arabian Peninsula in neighboring Yemen.
Four years later, his reported demise - in the remote and mountainous Hadramawt province - is a significant success for Yemen's armed forces in their re-energized campaign against AQAP and its allies in the south and east of the country.
Al-Shihri was the most senior Saudi figure in the group and important to its recruitment and fund-raising. And despite his relative youth (he was about 40) he had plenty of experience in jihadist circles. He had fought in Chechnya and trained in urban warfare at an al Qaeda camp near Kabul before the Taliban were overthrown.
According to local officials in Yemen, al-Shihri was killed by a U.S. drone strike against a car in which he and other militants were traveling, after being tracked for several days. It is further evidence of the growing liaison between the two governments since President Abdurabu Mansour Hadi took office earlier this year.
Al-Shihri's demise follows the killing of U.S.-educated al Qaeda propagandist Anwar al-Awlaki a year ago and senior operative Fahd al-Quso in May.
More recently there appears to have been a dramatic uptick in the U.S. drone campaign, often with controversial consequences. Just last week an air-strike killed 10 civilians in Rada'a, after missiles missed a vehicle carrying a local al Qaeda leader. Local tribal leaders blamed U.S. drones for the deaths.
But the expansion of the drone attacks has undoubtedly forced AQAP's leadership onto the back-foot.
Mustafa Alani, director of National Security and Terrorism at the Gulf Research Center, says U.S. drone strikes have done great damage to AQAP - much as they have to al Qaeda in Pakistan. One drone strike in August killed a Yemeni bomb-maker Abdullah Awad al-Masri who was suspected of assembling suicide vests and car bombs for use in attacks inside Yemen.
Six months ago, al Qaeda and its allies controlled several towns in the southern provinces of Abyan and Shabwah. A military offensive in the air and on the ground, supported by pro-government militia, has gradually uprooted these self-declared "Emirates." White House Counter-Terrorism Advisor John Brennan spoke of "unprecedented pressure" from Yemen's armed forces against AQAP.
President Hadi is gradually asserting control of the military to rein in the influence of relatives of his predecessor, Ali Abdullah Saleh, by seeking to give the better brigades more independence and their own budgets.
There are also signs of division and defections within AQAP.
A Gulf security analyst briefed by Saudi and other regional counterterrorism agencies tells CNN that a number of Saudis within AQAP have given up the fight in recent months. One of them was another former Guantanamo inmate, Adnan al-Sayegh, who gave himself up to Saudi authorities in late July.
According to the Saudi newspaper Al Hayat, al-Sayegh and other Saudi fighters disagreed with the focus on fighting the Yemeni military and had grown weary of constantly shifting locations to dodge drone strikes. In addition, in an atmosphere of growing distrust within the group, AQAP commanders had banned Saudi militants from making unsupervised phone calls to their families, according to the newspaper, for fear of infiltration.
In April a British mole within AQAP working for Saudi intelligence thwarted a plot by the group for him to target a U.S.-bound airliner on a suicide bombing. One senior official in the region said the bomb was more advanced than any the group had previously made.
No one is about to proclaim victory. Yemen's multi-layered crisis includes not only the most visceral threat of any al Qaeda franchise, but secessionist groups in the south, continuing tensions within the military and a desperate humanitarian situation.
And Time correspondent Casey Coombs wrote recently that some pro-government Popular Resistance Committees had quickly become disenchanted with a lack of support from the military. Brennan told the Council on Foreign Relations in Washington last month that the task was now for Yemeni forces to "hold and build" in areas cleared of al Qaeda fighters.
As it has been driven out of areas it controlled, AQAP has resorted to devastating suicide bombings in Yemen's major cities, and the assassination of pro-government militia leaders.
One Saturday morning last month a car approached the offices of Yemen's state broadcaster in the port city of Aden. It exploded, destroying a military vehicle outside. Militants then attacked the neighboring intelligence headquarters, detonating another car bomb in the process. At least 14 security officials were killed.
That followed attacks on military parades and police recruits in the capital that killed well over 100.
And there are still plenty of Saudi al Qaeda operatives in Yemen. They include the likes of Ibrahim al-Asiri, a master bomber suspected of building devices targeting U.S.-bound planes.
A Yemeni official told CNN that al-Asiri remains the greatest worry - especially as the most recent plot uncovered suggested he had mastered a new explosives formula.
Alani told CNN that an increasing number of Somalis had been killed or arrested inside Yemen in recent weeks, and that Somalis were among those arrested in August in a raid on a safe house in Jaar. "They are basically foot soldiers," he said.
Alani says AQAP's strategy is to withdraw from areas where it was under pressure and surge back when offered the opportunity. That may arise if the military and Popular Committees can't overcome their differences - or if intra-military rivalries flare up again.