SOLO, Indonesia—This city in central Java is ground zero in Indonesia’s fight against extremism.
One man—a native of this community of half a million people—financed and encouraged the terrorists who carried out the gun and bomb attacks against the capital, Jakarta, on Jan. 14. It wasn’t the first time Solo had incubated violent radicals.
Police said Bahrun Naim, an Islamic State adherent now based in Syria, sent money to the Jakarta attackers. Radicals from Solo, also known as Surakarta, were prominent in a wave of attacks against Western targets at the turn of the century, including the bombings on the resort island of Bali in 2002 that killed 202 people, mostly tourists.
Mr. Naim became radicalized while attending an Islamic school in Solo, local police and a person who knew him said. Over the past decade, Indonesian police have arrested or killed scores of local terrorists from a generation inspired by and linked to al Qaeda. Some had been to Afghanistan pre-9/11; many had studied in Solo. Improved policing eviscerated the leadership until only scattered cells capable of little more than drive-by shootings remained, experts said. Until last week there had been no major attack on Jakarta since 2009.
But the emergence of a new cohort of militants impressed as youngsters by the previous heyday of terror here demonstrates the deep roots of radicalization.