They rose up quickly to take up Osama bin Laden's call for jihad -- ruthless men in their 20s and 30s heralded as the next generation of global terror.
Two years after they were identified in an AP analysis as Islamic terrorism's young frontline leaders, five of the dozen militants are dead, targets of a worldwide crackdown that claimed its biggest victory with the killing this week of Abu Musab al-Zarqawi, al-Qaeda's frontman in Iraq.
Manhunts in Asia, Africa and Europe have pushed most of the rest deep underground; they are believed to have found refuge in places like the wartorn chaos of Somalia or the thick jungles of the southern Philippines.
While there will always be somebody willing to take up al-Qaeda's call to arms, analysts say the newcomers have fewer connections than the men they are replacing, less training and sparser resources.
And their degree of mutual allegiances -- the likelihood that they will seek to avenge or protect each other -- remains uncertain as well.
"There are more people popping up than are being put away," said Magnus Ranstorp, a terrorism expert at the Swedish National Defense College in Stockholm. "But the question is whether the new ones have the fortitude to take up the mantle and carry the struggle forward. I don't see that they have."
The 2004, AP analysis named the dozen as frontline leaders, their hands stained with the blood of attacks from Bali to Baghdad, Casablanca to Madrid.
Al-Zarqawi, who sat atop the 2004 list as the biggest threat after Osama bin Laden and his deputy Ayman al-Zawahri, died on Wednesday when US forces in Iraq dropped two massive bombs on his hideout northeast of Baghdad.
Tom Ridge, the former US Homeland Security chief, cautioned on Friday that governments can only reduce the risk from terrorism, not eliminate it.
"There will be a successor to bin Laden, as there will be a successor, unfortunately, to Zarqawi," he said in a speech in Paris. "There will be a successor to al-Qaeda."
But Ranstorp said it was far from clear if al-Zarqawi's replacement will have the contacts, resources or capacity to match the Jordanian terrorist's effectiveness at the helm of the biggest group of Iraqi insurgent forces.
"I'm not convinced that there is somebody ready to step in and fill Zarqawi's shoes," he said. "There may be, but it will take some time."
Globally, security forces have also had considerable success. Four of the other top 12 young militants in the 2004 list have met violent ends -- in shootouts in Saudi Arabia, under US bombardment in Fallujah, or in an Algerian terror sweep. The seven who remain at large are on the run, and none have been able to match al-Zarqawi's success at launching large-scale attacks since mid-2004.
Counterterrorism officials warn that others have since emerged as equally or more dangerous, and that the global fight against Islamic militancy is far from won. But tracking the fate of the 12 terror leaders gives an insight into the ever-changing landscape of Islamic militancy, and the short life expectancy of those who choose to take up arms in this way.
On the roll call of dead militant leaders is Nabil Sahraoui, who took over the North African Salafist Group for Call and Combat in a 2004 coup, and quickly announced that he was merging it with al-Qaeda. Sahraoui didn't have much time to savor his power play. The militant in his 30s was gunned down by Algerian troops that same year in a massive sweep east of Algiers.