Jemaah Islamiah, the group most likely to have carried out the Bali bomb attacks on 1 October, has in recent months been beset by internal disputes over ideology and the use of violence.
By David Wright-Neville
Monash University, Melbourne
Ji is the main suspect behind the latest attacks in Bali
Successful counter-terrorism operations by Indonesian authorities have also increased pressure on the organisation.
But the latest bombings suggest that hardliners within the group remain both willing and able to use deadly force to promote their agenda.
Jemaah Islamiah (JI) has a long track record of bomb attacks, the most notorious of which were the near simultaneous blasts in two Balinese nightclubs on 12 October 2002, in which more than 200 people were killed, including 88 Australians.
More recently, JI has been implicated in attacks against Christian targets in eastern Indonesia, a suicide bombing outside the Australian embassy in Jakarta in September 2004 and a similar strike at the JW Marriott hotel, also in Jakarta, in August 2003.
However, JI has not been without its problems. In particular, there is a growing schism between those JI members who want to continue to use violence to secure their goals and a growing sector unhappy at the disproportionately large number of unintended Muslim victims of such violence.
Indonesian security analysts report that the organisation has split into two broad factions - bombers and proselytisers. The latter are attempting to steer the organisation towards using preaching as its main weapon.
JI is alleged to have established cells throughout the region
Adding to these internal divisions has been the sustained pressure applied to JI by Indonesian counter-terrorism agencies, often in concert with counterparts from further afield, notably the US, Australia and other South East Asian states.
This pressure has led to more than 200 arrests of suspected JI members across the region.
Critical among these has been the detention of JI's alleged spiritual leader, Abu Bakar Ba'asyir, currently serving two years jail on minor charges stemming from the Bali attacks in 2002.
The capture of logistics chief Riduan Isamuddin, also known as Hambali, arrested in Thailand and now in US custody, and the death of a senior bomb maker, Fathur Rahman al Ghozi, killed in a shoot-out with police in the Philippines, have also been important.
But a number of key figures with the logistic and technical expertise required to sustain a level of deadly violence remain at large.
Of particular interest to the authorities are two Malaysian JI members - Dr Azahari Husin and Noordin Mohamed Top - whom Australian forensic experts have implicated in both the Marriott and Australian embassy attacks.
A UK-trained engineer and former university lecturer, Azahari is an explosives expert who adapted his academic training to terrorist trade craft at al-Qaeda run camps in Afghanistan in the 1990s.
South East Asian intelligence sources say that Azahari, along with the former accountant Noordin Top, have come to play increasingly important roles within the organisation, filling the operational and logistic vacuum left by those who have eschewed violence, and the arrests or deaths of others.
The militant factions are now looking outside JI for bombers, as the pool of potential attackers shrinks.
For instance, the suicide bomber who drove the van to the Australian embassy in Jakarta is thought to have been recruited from outside the formal JI structure.
JI is said to have been formed in Malaysia in the late 1980s, by a handful of exiled Indonesian extremists.
The network has since grown to include cells across the Indonesian archipelago, Malaysia, the Philippines, Singapore and Thailand. Smaller cells might also exist in Cambodia, Vietnam, and possibly even in Australia.
Its goal is the establishment of an Islamic state in Indonesia and in other parts of South East Asia. In its formative years JI advocated using largely peaceful means to pursue these goals, but in the mid-1990s the group took on a more violent edge.
This growing militancy was nurtured in part through contacts between JI figures, and senior al-Qaeda personnel then in Afghanistan.
Under the influence of the latter, JI embraced the idea that its goals could only be secured through a "holy war".
There is still no reliable information on the number of JI members, with estimates ranging from several hundred to several thousand. The actual number probably lies somewhere between the two, with the majority scattered across Indonesia.
There are several reasons for JI's durability, one of which is its ability to tap into a general feeling that South East Asian Muslims are victims of a larger anti-Islamic conspiracy led by the US and supported by allies such as the UK and Australia.
Indeed a recent al-Qaeda-linked website urged South East Asian groups to prioritise Australian targets.
While parallels will inevitably be drawn between al-Qaeda's hubris and JI's regular attacks against Western targets, there is still little credible evidence to support the claim that the JI is al-Qaeda's "South East Asian wing".
It is true that links between senior JI operatives and al-Qaeda stretch back a decade.
In fact it was the simultaneous presence at al-Qaeda camps in Afghanistan by militants from across South East Asia that facilitated many of the personal relationships that exist between JI and members of other violent South East Asian Islamist groups.
These include the Moro Islamic Liberation Front, a secessionist movement fighting for a Muslim homeland in the southern Philippines, as well as several other Indonesian, Malaysian and Thai groups.
But the weight of evidence suggests that although some JI personnel might be inspired by the larger global mystique of figures such as Osama bin Laden, the South East Asian group remains operationally and organisationally distinct.