He says he’s just simple preacher. But on Thursday, Abubakar Ba’asyir, the man widely considered the grandfather of Islamic militancy in Indonesia, was convicted on terror charges and sentenced to 15 years. Ba’asyir, 72, was charged with founding and financing a militant group that ran a terrorist camp in Aceh, northern Sumatra. The group, which called itself Al Qaeda of the Veranda of Mecca, was raided last year, resulting in more than 100 arrests. Ba’asyir, who was previously held in connection with the Bali Bombings, dismissed the judgement, saying it was based on laws made by “infidels,” not the laws of Islam. He smiled as he left the courtroom.
Today’s verdict is, in some ways, a victory for Indonesia. Since the bold and bloody Bali Bombings of 2002, the archipelago nation has been under tremendous pressure to tackle terrorism. In 2003, with support from the United States and Australia, Indonesia formed Detachment 88, a counter-terror squad staffed by the elite of the country’s police and special forces. The unit has earned acclaim for its success building an extensive intelligence network and conducting undercover operations. They’ve arrested, detained or killed hundreds of leaders and foot soldiers. They’ve also made modest strides in de-radicalization. “You want to know why Indonesia has done well fighting terrorism? We have no Guantánamo prisons,” psychologist Sarlito Wirawan Sarwono, who instructs Detachment 88 officers in interrogation tactics told TIME last year. “Our police understand the terrorists’ psyches.”
To an extent, sure. But the threat persists. Even as cells are shuttered, or clerics tried, new groups emerge. Maria Ressa, an expert on radical Islam in Indonesia likens it to the spread of a virus: The ‘jihadi virus’ grew out of the crucible of Afghanistan, she says, and was carried to Southeast Asia by veterans who trained and taught in the Philippines and elsewhere. Their ideology passed, friend to friend, family to family, changing as it spread. “The virus is resilient,” she told me recently. “It mutates.”
Indeed, as the crackdown presses on and leaders like Ba’asyir are jailed, extremist groups adapt. Recent attacks have been relatively low-tech and have focused on local, rather than international, targets. In March, a series of ‘book bombs’ (hollowed-out books stuffed with explosives) were sent to four Indonesians — a politician, a counter-terror expert, the chair of a youth organization and a singer. In April, a suicide bomber attacked a police mosque in Cirebon, killing himself and inuring 30 others. “This is part of a pattern of do-it-yourself jihad,” Sidney Jones, a terrorism expert at the International Crisis Group, told TIME. “It falls under the ideological precept of jihad fardiyaor individual jihad, and I’m afraid we will see more of them.” The key, she says, it to focus on prevention, to stop people from joining up in the first place. Without a major counter-radicalization effort, people will continue to buy in to Ba’asyir’s ideology. The preacher is in prison, but his word spreads still.
More on TIME.com: See TIME’s 2002 interview with Abubakar Ba’asyir