COPENHAGEN — If Al Qaeda strikes the West in the coming months, it's likely the mastermind will be a stocky Egyptian explosives expert with two missing fingers.
His alias is Abu Ubaida al Masri. Hardly anyone has heard of him outside a select circle of anti-terrorism officials and Islamic militants. But as chief of external operations for Al Qaeda, investigators say, he has one of the most dangerous -- and endangered -- jobs in international terrorism.
He has overseen the major plots that the network needs to stay viable, investigators say: the London transportation bombings in 2005, a foiled transatlantic "spectacular" aimed at U.S.-bound planes in 2006, and an aborted plot in this serene Scandinavian capital last fall.
But pursuers have captured or killed his predecessors and have been gunning for him. He prowls Pakistani badlands one step ahead of satellites and security forces.
Although periodic reports of his death have proved false, rumors resurfaced after recent American airstrikes. Asked whether Masri is alive, a Western anti-terrorism official said, "It's a question mark."
Masri himself can be described that way. Authorities know only bits and pieces of his biography. They know his face, having identified an unreleased photo, but not his real name.
"He is considered capable and dangerous," said a British official, who like others in this report declined to be identified. "He is not at the very top of Al Qaeda, but has been part of the core circle for a long time. He is someone who has emerged and grabbed our attention as others were caught or eliminated in the last couple of years. Perhaps he rose faster than he would have otherwise."
The Times has charted Masri's rise in interviews with anti-terrorism officials and experts from Europe, the United States and the Middle East, and a review of case files and academic and intelligence reports. The stories of man and network intertwine, revealing the dangers and vulnerabilities of both.
Masri's emergence reflects Al Qaeda's resilient, hydra-like structure. As leaders fall, mid-level chiefs step up, shifting tactics and targets with determination and innovation.
But Al Qaeda seems diminished despite insistent propaganda and an onslaught of violence in Iraq, South Asia and North Africa. The network has not pulled off an attack in the West since 2005.
"We have to be careful not to fall prey to our fears," said a senior British anti-terrorism official. "The language of 2001, 2002, gave an inflated view of Al Qaeda's size and structure. It's not the Red Army, it's not even the Irish Republican Army. . . . There have been advances by AQ at the ideological level, it has spawned franchises, but don't lose sight of the operational setbacks that AQ has suffered."
The plots attributed to Masri were ambitious, but authorities infiltrated two cells long before they could strike. Some trainees seemed more fierce than talented. And the number of seasoned field commanders dwindles, former CIA officer Marc Sageman said in an interview.
"Al Qaeda's bench is shrinking," Sageman writes in his latest book, "Leaderless Jihad." "Yes, there are trained and still quite competent terrorist trainers around, and they are more visible in Waziristan [in Pakistan], but the long-term prospect of Al Qaeda central in the Afghan-Pakistani theater is diminishing."
But other experts see signs of resurgence. Last year, U.S. spy agencies warned that Al Qaeda had "protected or regenerated" its leadership and ability to attack the United States by carving out a haven in Pakistani tribal areas.
Masri is in his mid-40s, according to an Italian translation of a German investigative file. His nom de guerre means "The Egyptian Father of Ubaida." Little is known about his youth. He belongs to a generation of Egyptians who have dominated Al Qaeda since they fought the Soviets in Afghanistan, officials say.
Masri followed the classic itinerary after Afghanistan, officials say. He fought in Bosnia-Herzegovina in the early 1990s, went on to Chechnya and was wounded, according to the Italian file. He lost two fingers -- a common disfigurement suffered by Al Qaeda veterans from combat or explosives. Masri also spent time in Britain, according to the file. In 1995, he surfaced in Munich, Germany, under an alias and requested asylum. His associates there included a Moroccan computer science student who married the daughter of Ayman Zawahiri, Osama bin Laden's deputy, and Jordanian operatives who led a 2002 plot for shooting attacks on Jews.
In 1999, authorities rejected Masri's asylum claim and jailed him pending deportation. But he was released instead for reasons that are unclear.
Tanned and muscular