The leader of radical Sunni fighters who have made rapid military advances in Iraq is the rising star of global jihad, driven, Islamist fighters say, by an unbending determination to fight for and establish a hardline Islamic state.
Abu Bakr al-Baghdadi, commander of the Islamic State in Iraq and the Levant (ISIL), now controls large parts of eastern Syria and western Iraq, a vast cross-border haven for militants in the Sunni Muslim core of the Middle East.
Despite his power - and a US$10 million US reward for information leading to his capture - little is known about a man who for his own survival has shunned the spotlight.
Fighters from ISIL and its rivals who spoke to Reuters praised Baghdadi as a strategist who succeeded in exploiting turmoil in Syria and Iraq's weak central authority after the US military withdrawal to carve out his powerbase.
He has proved ruthless in eliminating opponents and showed no hesitation in turning against former allies to further his ambition of creating an Islamist state.
Enemies, even those from rival radical groups who broadly share ISIL's religious ideology, are fought and defeated. Captured fighters - and non-combatants - are usually shot or decapitated, their deaths recorded in grisly videos which inspire fear and revulsion among opponents.
"In short, for Sheikh Baghdadi, each religion has its state except Islam, and it should have a state and it should be imposed. It is very simple," said one of his non-Syrian members, speaking from inside Syria.
According to the US reward notice, which depicts a round-faced, brown-eyed man with closely cropped beard and short dark hair, Baghdadi was born in the Iraqi town of Samarra in 1971.
He got a doctorate in Islamic studies at Baghdad university, jihadi websites say, and after years of fighting with al Qaeda groups became leader of its Islamic State in Iraq in 2010.
A year later, sensing opportunity when the uprising against Syrian President Bashar al-Assad erupted, Baghdadi sent an aide across the border to expand al Qaeda's foothold there.
That aide, Abu Mohammad al-Golani, set up al Qaeda's Nusra Front which quickly rose to prominence with a series of deadly car bombings. It also earned a reputation as the most effective of the many disparate forces fighting Assad.
But as Golani grew strong in Syria and rejected an edict to merge his forces under Baghdadi's command, Baghdadi launched a war against the Nusra Front, leading to a split with al Qaeda leader Ayman al-Zawahri.
For many of Baghdadi's supporters the clash between their battlefield commander and the nominal but distant al Qaeda leader, who tried in vain to impose his authority to end the dispute, was no surprise.
When al Qaeda founder Osama bin Laden was killed by US forces in Pakistan three years ago, Baghdadi "was the only one who did not pledge allegiance to Zawahri," the non-Syrian ISIL member said.
"He was assigned by Sheikh Osama to establish the state, this was his plan before he (bin Laden) was killed."
While Baghdadi's supporters believe an Islamic state would revive the glories of Islam under the Prophet Mohammad, they say Zawahri feared that by drawing jihadi fighters together in one place it would make it easier for the West to defeat them.
His fighters counter that Baghdadi has plenty of hidden surprises for his enemies. "He has capabilities that he keeps secret until the right time," another ISIL supporter said.
GROWING IN STRENGTH
Ignoring Zawahri's calls to leave Syria to the Nusra Front, Baghdadi expanded operations across northern and eastern parts of Syria in 2012 and 2013, sometimes battling Assad's forces but more often pushing out other rebel fighters.
ISIL's unforgiving treatment of ordinary Syrians won it many enemies and by the end of last year an alliance of Nusra and other Islamist brigades struck back, pushing ISIL back to its stronghold along the Euphrates River in the oil producing deserts of eastern Syria.
But ISIL has grown stronger, not weaker. Baghdadi's fighters control the city of Raqqa - Syria's only provincial capital completely beyond Assad's control - and have imposed strict Islamic law.
In neighbouring Deir al-Zor province ISIL has waged a six-week offensive against rival rebels in which 600 fighters have been killed, seizing oilfields and towns on the north-east bank of the Euphrates 100km from the Iraqi border.
Oil sold on the black market provides millions of dollars in revenues, rebels say. Combined with Iraqi recruits and the military equipment seized in his capture of the Iraqi city of Mosul, Baghdadi now has a formidable array of resources.
Supporters say that is key to achieving his aim of military self-sufficiency, ensuring an independent flow of money, manpower, weapons and energy supplies.
RIVAL TO ZAWAHRI
Baghdadi's real and very visible strength stands in sharp contrast to Zawahri, in hiding for more than a decade and trying to influence a global jihad most of which is played out a long way from his refuge.
Even Baghdadi's rivals say the ISIL leader is in the ascendancy, winning influence well beyond Syria and Iraq.
"He is becoming very popular among jihadis. They see him as someone who is fighting the war of Islam," said a Nusra Front fighter from the Syrian city of Aleppo, adding bitterly that Baghdadi's supporters "cannot see the damage he is inflicting".
"He has received letters expressing loyalty from Afghanistan and Pakistan as well," the Nusra fighter said. "Sheikh Zawahri is trying but I think it is too late."
From Nusra's perspective, Islamists in Syria have "entered a cycle of blood and nobody will come out of it," he added.
To his followers, Baghdadi represents a new generation of fighters working to fulfil the next stage of bin Laden's dream, moving from Qaeda - which can mean 'base' in Arabic - towards the fully fledged radical state.
"Sheikh Baghdadi and Sheikh Osama are similar. They always look ahead, they both seek an Islamic state," said a Syrian ISIL fighter.
Others go further, saying Baghdadi's creation of ISIL makes Zawahri's part of al Qaeda's operation redundant.
"The group al Qaeda does not exist any more. It was formed as a qaeda (base) for the Islamic State and now we have it, Zawahri should pledge allegiance to Sheikh Baghdadi," said the non-Syrian ISIL fighter.
Another jihadi who described himself as close to Baghdadi said Zawahri was watching, powerless, to see whether the ISIL leader makes a false move. "He is waiting to see if Baghdadi will win or fall, but in either case he is no longer leader."
"WORLD SHOULD FEAR HIM"
Among his strategies, Baghdadi has opened the door to foreign fighters, particularly Europeans and Americans, providing them with training and a sense of purpose.
While they are useful on the Syrian battlefield, they may also head back home one day, war veterans with experience to recruit others to carry out attacks for Baghdadi outside the Middle East.
They are trained to be fearless and merciless. Activists in several areas inside Syria say that Baghdadi's men walk around wearing explosive vests.
In a sign of their brutality, a video posted on the internet shows ISIL fighters, some of whom do not appear to speak Arabic, executing several men. Two victims were reciting the Shahada, the Muslim declaration of faith, as they were killed.
Many clerics say it is forbidden to kill a person while they declare the Shahada, but Baghdadi's men operate by a simpler rule: whoever stands in their way should be terminated, regardless of religion or sect.
Asked how serious Baghdadi is, a supporter replied: "When you have his army, his determination and his belief then the world should fear you."
"If the world does not fear Baghdadi then they are fools, they do not know what will hit them in the future."