It’s not surprising that ISIS leader Abu Bakr al-Baghdadi keeps a low profile, considering the fate of his predecessors. Abu Musab al-Zarqawi, the original leader of what was then called al-Qaida in Iraq, was killed by a U.S. bomb in 2006. His successors, Abu Ayyub al-Masri and Abu Omar al-Baghdadi, met their end in an attack by U.S. and Iraqi forces west of Baghdad in 2010.

All the same, the dearth of information about Baghdad is as remarkable as the speed of his rise to prominence. In just five years, Baghdadi has gone from a low-level fighter considered a minor enough risk that he was released by U.S. forces to being called the “world’s most influential militant” and the “true heir to Osama bin Laden.”

There are only two known photos of the 43-year-old Baghdadi, who Iraqi military officials believe is hiding somewhere in Iraq’s eastern Diyala province. An “official” biography of Baghdadi, whose real name is Ibrahim Awwad Ibrahim Ali al-Badri al-Samarrai, that has circulated on jihadist forums says he earned a doctorate in Islamic studies and lectured on Shariah before becoming a militant. Some other accounts say he was a peasant who was trained by members of al-Qaida when he was in prison.

Baghdadi fought in some capacity with Sunni militant groups after the U.S. invasion of Iraq but was arrested in 2005 and interred by U.S. forces at Camp Bucca, the main U.S. detention facility after the closing of Abu Ghraib. He wasn’t considered much of a threat and was released in 2009. The former commanding officer of Camp Bucca recently told the Daily Beast that when Baghdadi was released, he told his captors, “I’ll see you guys in New York.” (The guards at the prison were from a Long Island-based military police unit.) The commander, Col. Kenneth King, says Baghdadi “was a bad dude, but he wasn’t the worst of the worst” and is surprised he rose to such prominence.

It seems as if Baghdadi became far more involved with al-Qaida in Iraq while imprisoned than he had been before, to the point that he took over the group after the deaths of Masri and the other Baghdadi a year later. In 2011 he was designated as a global terrorist by the U.S. State Department with a $10 million bounty.

Things really picked up in 2012, when, sensing an opportunity, Baghdadi dispatched some foot soldiers to join the fighting against Bashar al-Assad’s government in Syria. In 2013 he announced that the group was merging with Jabhat al-Nusra, the other al-Qaida affiliate in Syria, to form a new group called the Islamic State in Iraq and al-Sham. (al-Sham refers to “Greater Syria” and has been translated as either Syria or the Levant in the English-language press. Locals often refer to the group using the acronym Da’ash, a crime which is reportedly punishable by flogging in ISIS-controlled areas. )

This was a fairly audacious move considering that he doesn’t seem to have run it by either the leaders of Nusra or al-Qaida’s global leader Ayman al-Zawahiri. Nusra, predominantly Syrian in membership, is more focused on the overthrow of Assad, whereas ISIS is more international and interested in expanding its territory and enforcing Shariah. Zawahiri formally disavowed ISIS earlier this year, but it has clearly become the more dominant group in Syria, eclipsing the once-formidable Nusra.

Under Baghdadi, ISIS’s approach to governance is an odd mix of terror and charm offensive: It has provided food aid and below-market-value fuel—branded with the group’s black flag—and sponsored fairs for local children at the same time it has boasted of the summary execution of hundreds and enforced its extremely narrow interpretation of Shariah with floggings and amputations.

Baghdadi clearly was shrewd in taking advantage of Syria’s chaos to grow his organization, but it seems pretty obvious that the group’s new prominence didn’t just emerge out of nowhere. In addition to gathering weaponry and money from areas captured, it seems likely that ISIS has been tapping into al-Qaida central’s revenue stream for some time.

Zawihiri, Bin Laden’s formal successor, seems more sidelined than ever in his Pakistani redoubt as dynamic new groups in Syria, Iraq, Yemen, Somalia, the Maghreb, and West Africa increasingly orchestrate operations on their own. So is Baghdadi the true heir?

Unlike Bin Laden, he doesn’t seem to have much influence beyond his immediate battlefield in Syria and Iraq, though reports of an “ISIS cell” being broken up in Madrid today may indicate more international ambitions. My guess is that the group’s leader won’t be a man of mystery for much longer.