From 1948 to the early 1960s when its back was broken, Darul Islam was the group that Muslim radicals would join to pursue a dream of Indonesia as an Islamic state.
When President Suharto fell in May 1998, the advent of free speech and assembly and the activities of some enterprising military intelligence operatives helped nurture new groups.
Thus thousands of eager young Muslim men went to fight Christian compatriots in the Maluku Islands from early 1999.
In time-honoured fashion, true believers pursued their cause, corrupt security forces profited and the world largely ignored the destruction of hundreds of communities and thousands of lives in a little-known religious war.
That neglect, and the incompetence of investigations into bombings across the country in 1999 and 2000, has come back to haunt not just Indonesia but the region as a whole.
Behind the scenes, a far more ambitious plan was afoot - the cross-border marriage of religious fanaticism with battle-hardened explosives skills in the resurrected cause of an Islamic caliphate across Southeast Asia.
This is Jemaah Islamiah, says the Jakarta office of the International Crisis Group, a Brussels-based think-tank which has just produced a second report on the roots of Islamic rebellion in Southeast Asia through analysis of trial documents, police reports and its own interviews with an impressive range of contacts.