Intelligence sources say it’s hard to exaggerate the importance of Hambali’s capture. They explain he was not only the “operational mastermind” of Al Qaeda’s Southeast Asian affiliate, Jemaah Islamiah, but he was also Osama bin Laden’s senior representative in the region. The 39-year-old native of West Java has been implicated in planning the 9/11 attacks, the nightclub bombings that killed some 200 people on the island of Bali in October 2002 and other deadly terrorist incidents. He could help to answer many questions about those attacks and to unravel other plots that were planned but not yet executed. newsweek has learned that at least one major Qaeda detainee has alleged that Hambali was assigned to recruit additional teams of hijackers for follow-up attacks on U.S. targets after 9/11. A U.S. official says those allegations have been corroborated by other intelligence and are believed credible.

Hambali began life as Encep Nurjaman, one of 12 children born into the family of a village schoolteacher. (He’s often identified in press accounts by another alias, Riduan Issamuddin.) Neighbors recall him as “a taciturn, obedient boy.” He was about 20 when he migrated to Malaysia and met up with a militant Islamic preacher who had fled the repressive regime of Suharto, the U.S.- backed dictator who then ruled Indonesia. By the late 1980s, Hambali had joined the anti-Soviet resistance in Afghanistan. One of his closest associates was Khalid Sheikh Mohammed, then a roving operative and later one of bin Laden’s top planners. After the war, the Indonesian returned to Malaysia and began calling for a holy war against America.

Hambali was a doer, not just a talker. Intelligence specialists believe he was in charge of logistics and accommodations for the now notorious January 2000 terror-planning session in Kuala Lumpur. It was there that at least two future 9/11 hijackers would meet with other Qaeda operatives, including one called “Khallad,” the architect of the USS Cole bombing. U.S. officials say Hambali also had a hand in a deadly series of church bombings on Christmas 2000 in Indonesia and the Philippines. “Hambali … has been involved in every major terrorist plot in the region,” says Andrew Tan, a security analyst for the Institute of Defence and Strategic Studies in Singapore.

Still, the problems that Hambali represents are still there. Thai authorities wish his capture would prevent whatever atrocities he was planning–but they aren’t betting on it. “You can’t be sure because he’s been working for quite some time,” says the Thai police source. “We don’t know if he’s got things set up [for an attack] or not.” And the groups remain. “It is a mistake to think that Hambali’s arrest will reduce the threat of terror in Southeast Asia,” says Tan. “Jemaah Islamiah believes in ’leaderless resistance.’ Although 200 JI operatives have been arrested so far, 500 to 1,000 members have gone through terrorist training. Others will take the places of those arrested.” Presumably, Hambali knows their names.