But the only group to carry out high profile attacks on Western targets in Indonesia's capital in the past has been the Jemaah Islamiyah (JI), and most analysts expect the attackers will be found to be part of the group's network. The JI had attacked the Jakarta Marriott once before, killing 20 people there with a suicide car bomb in 2003.
Counter-terrorism efforts in Indonesia and in neighboring countries where the groups members have operated – Singapore, Malaysia, and the Philippines have all arrested JI members on their own soil – had proven successful until now. Friday's attack was the first terrorist incident in the country in four years.
Is it possible that another wave of JI attacks are in the offing?
What is JI?
Jemaah Islamiyah means simply "Islamic Group" and the organization's ideological roots stretch back to Indonesian independence at the end of World War II. Indonesia then as now was the most populous Muslim-majority nation in the world. In West Java, part of Indonesia's most populous island, a number of local preachers and their followers who were influenced by the austere brand of Islam practiced in Saudi Arabia were angry that the new nation had not been made an Islamic State and took up arms against the new nation until being decisively and brutally crushed in the 1950s.
The survivors of this earlier movement, called the Darul Islam ("House of Islam"), continued to be a thorn in the side of the Indonesian state for years, occasionally carrying out attacks and organizing through a tightly-knit group of Islamic boarding schools and mosques. Though their views have evolved over time, the ideological forefathers of the group today saw the military dictatorship that ruled Indonesia until the fall of Suharto in 1998 as irredeemably godless and corrupt and the only acceptable form of government to be, ultimately, an Islamic caliphate. Their views have also generally been hostile to Indonesia's Christians.
The modern terrorist group evolved from a circle of Indonesian clerics and supporters who were exiled to Malaysia in the 70s and 80s for their Islamic activism. Within days of Suharto's fall, they made plans to come home and try to seize control.
Who are they?
The movement's surviving spiritual leader is Abu Bakar Bashir, who remains a free man and says he has never carried out a terrorist attack and that he simply broadcasts a call to jihad – or holy war – to protect Islam from its enemies. Some analysts believe that Mr. Bashir's influence has waned in recent years, as the operatives who gathered around him in Malaysia have been killed or captured. The most prominent of the activists still at large who were suspected of involvement in past JI attacks is Noordin Mohammed Top a Malaysian national who officials in Indonesia and Singapore have accused of playing a key financing and logistical role in major attacks like the 2002 Bali bombing that killed 200 people and the 2003 Marriott attack.
Indonesian officials said in 2006 that Mr. Top considered himself to be the leader of his own militant group and intelligence analysts have said that if JI attacks were to resume, the structure and leadership of the group would probably be radically different than in the past.
What are they fighting for?
What they want is an Islamic state that, eventually, spans the globe. But for the moment they'll settle for a caliphate in the Islamic parts of Southeast Asia – Indonesia, Singapore, Malaysia, Southern Thailand and the Southern Philippines. Accomplishing this goal is far from likely, of course. Sidney Jones, a leading expert on militant groups in Indonesia at the International Crisis Group, has estimated that hard core supporters of JI are probably below 1,000.
Do they have a new strategy?
Successful terrorist groups are always adapting their tactics to circumvent new security measures, and there was evidence of that in today's attack. The men who carried it out checked into the Marriott ahead of time with bombs sufficiently broken down that they were able to evade detection by the lobby metal detectors, then quietly assembled them in the room they took on the 18th floor. In the past, JI attacks have involved suicide bombers, either on foot or in cars ramming front gates or wandering in to lightly guarded cafes.
But as to strategy, there is probably no change. Their rather unlikely hope is that terrorist attacks will so weaken the economy and legitimacy of the Indonesian government that the general public will turn to their rather extreme vision of Islamic government. Indonesia's tourism industry, an economic mainstay, has continued to grow after each JI attack in the past.
What is being done to stop them?
Detachment 88 is the Indonesian government's primary anti-terrorism group, and has been widely praised in recent years for its success against JI.
The US-trained police unit has captured hundreds of JI operatives in the past. When the first major JI attacks began in 2002 and 2003, the Indonesian police had limited ability to track terrorist groups, both in terms of networks of informants inside the right organizations, but also an absence of computer systems or other organized national databases. The detachment also received traditional forensic training from Australia, which lost 88 of its citizens in the 2003 Bali bombing.
Years ago, Indonesian bombing scenes were sloppily secured, if at all, and physical evidence was often damaged or contaminated by onlookers.
Today, reporters in Jakarta said they were frustrated to be kept over a 100 yards away form the hotels shortly after the bombs were placed.