For nearly three years the United States has had a $10 million bounty on the man who has emerged as the leader of Islamic insurgents, even though American authorities had him in custody during the U.S. war in Iraq.
U.S. military authorities captured the man known by his nom de guerre, Abu Bakr al-Baghdadi, in 2005, and held him for four years at Camp Bucca, detention center the U.S. was operating in southern Iraq.
But as the United States wound down combat operations in Iraq, former President George W. Bush signed an agreement turning over all detainees to the Iraqis, who released Baghdadi in 2010.
That year Baghdadi assumed leadership of the Islamic State of Iraq and the Levant (ISIL), the group that has taken control of large swathes of Iraq and Syria.
ISIL poses a great threat to the Baghdad government as the militants seek to impose a Sunni Islam caliphate across the Middle East.
The U.S. officially designated Baghdadi a terrorist in 2011 and offered the $10 million reward for his capture or killing.
Baghdadi is believed to have been born in Samarra, north of Baghdad, in 1971, with the name Awwad Ibrahim Ali al-Badri al-Samarrai.
He obtained a doctoral degree in Islamic studies and history at an Islamist university in Baghdad, perhaps accounting for why several of his aliases include the title "Dr."
Some news accounts say he was a cleric in a mosque at the time of the U.S. invasion of Iraq in 2003, and possibly already a militant jihadist during the rule of Saddam Hussein, the Iraqi leader toppled by the U.S. and eventually executed. The circumstances of Baghdadi's apprehension by the U.S. are not publicly known, but some analysts say he may have been radicalized while held by the U.S.
He has rarely been seen in public, but a video was posted Saturday on radical Islamist websites purporting to show him giving a sermon Friday at a mosque in Mosul, Iraq's second largest city captured last month by the ISIL insurgents.
He appealed to his followers to help him if he is right, and put him "on the right path" if he is wrong.
"It is a burden to accept this empowerment to be in charge of you. I am not better than you or more virtuous than you," Baghdadi said. "If you see me on the right path, help me. If you see me on the wrong path, advise me and halt me. And obey me as far as I obey God."
Baghdadi has declared an Islamic "caliphate" in northern Iraq and Syria, calling on the world's Muslims to emigrate there and take up arms.