By Lucy Williamson
BBC News, Jakarta
Abu Dujana is thought to be JI's military leader
Two of the most senior operatives from the Islamic militant group Jemaah Islamiah are now believed to be sitting in custody in Indonesia.
Abu Dujana, the man police describe as the terrorist suspect they most wanted to catch, is waiting to answer questions about a string of bomb attacks in the country.
So too is the alleged leader of the group, a man known as Zarkasih.
Police say both men have valuable information about the workings of Jemaah Islamiah (JI), Indonesia's most active militant group.
But the question burning most in minds here is what effect these arrests will have on the shadowy organisation.
Jemaah Islamiah is widely blamed for the 2002 attacks in Bali, that killed more than 200 people, as well as bombings in Jakarta and Sulawesi.
But little concrete information is known about who exactly runs it, and how its different parts are linked.
Both men were among eight suspects arrested during raids on the island of Java in early June.
Zarkasih is believed to have taken the top role in JI in recent years
Most observers say their arrests will be a severe blow to JI.
Sidney Jones, the head of the International Crisis Group in Indonesia, said the men know "virtually every single bit of information that's known about JI."
Many analysts believe that, even before these two men were captured, JI had already been weakened due to a spate of arrests by counter-terrorism forces here.
Hundreds of suspected militants have been arrested or killed, including high profile figures like JI bomb-maker Azahari Husin.
KEY JI FIGURES
Noordin Mohamed Top, bomb maker and head of splinter group, still on run
Dulmatin, in hiding in the southern Philippines
Alleged leader Zarkasih, in police custody
Alleged military leader Abu Dujana, in police custody
Bomb expert Azahari Husin shot dead by police in 2005
Abu Bakar Ba'ashir, alleged JI spiritual leader, released from jail in 2006
Amrozi, Imam Samudra and Ali Ghufron on death row for 2002 Bali bombings
Hambali, alleged JI operations chief, held in Guantanamo Bay
And that is another reason, says Sidney Jones, why the capture of Zarkasih and Abu Dujana could hurt the organisation.
Not only are they alleged to be some of its most senior members, but they are both seen as men with experience of previous operations, and past links to al-Qaeda - men who trained for several years in Afghanistan's mujahideen camps.
Experience like this, she says, is now in increasingly short supply for groups like JI.
Since the Bali nightclub bombings in 2002, which killed 202 people, internal splits are thought to have grown within JI.
That may make it harder for the group to launch attacks on the same kind of scale as the Bali bombings, but it has also made it harder for the security forces to track them.
The splits have led to the rise of smaller, more extreme, splinter groups like that believed to be led by Noordin Mohamed Top.
He has been described as the number one fugitive in South East Asia, and he is still at large.
Jemaah Islamiah has been blamed for the Bali attack in October 2002
The fact that JI, and other groups like it, are still able to launch deadly attacks was highlighted earlier this year when security forces found large amounts of bomb-making materials during raids on JI hideouts.
Police say there was enough material to dwarf previous bomb attacks in the country.
The capture of Zarkasih and Abu Dujana could expose the long-secret workings of the group's highest echelons, but it will not stop recruitment or solve the problem facing police here.