(FILES) This image grab taken from a propaganda video released on July 5, 2014 by al-Furqan Media allegedly shows the leader of the Islamic State (IS) jihadist group, Abu Bakr al-Baghdadi, aka Caliph Ibrahim, adressing Muslim worshippers at a mosque in the militant-held northern Iraqi city of Mosul. 
The Russian army on June 16, 2017 said it hit Islamic State leaders in an airstrike in Syria last month and was seeking to verify whether IS chief Abu Bakr al-Baghdadi had been killed. In a statement, the army said Sukhoi warplanes carried out a 10-minute night-time strike on May 28 at a location near Raqa, where IS leaders had gathered to plan a pullout by militants from the group's stronghold.
 / AFP PHOTO / AL-FURQAN MEDIA / --/AFP/Getty Images
(FILES) This image grab taken from a propaganda video released on July 5, 2014 by al-Furqan Media allegedly shows the leader of the Islamic State (IS) jihadist group, Abu Bakr al-Baghdadi, aka Caliph Ibrahim, adressing Muslim worshippers at a mosque in the militant-held northern Iraqi city of Mosul. The Russian army on June 16, 2017 said it hit Islamic State leaders in an airstrike in Syria last month and was seeking to verify whether IS chief Abu Bakr al-Baghdadi had been killed. In a statement, the army said Sukhoi warplanes carried out a 10-minute night-time strike on May 28 at a location near Raqa, where IS leaders had gathered to plan a pullout by militants from the group's stronghold. / AFP PHOTO / AL-FURQAN MEDIA / --/AFP/Getty Images
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(CNN) —  

A preacher of hate. The instigator and inspirer of some of the most hideous acts of violence ever put to video. An elusive fugitive, hunted by drones, only once seen in public. The perverter of Islam with a nauseatingly infectious ideology that had a greater lure to a disenfranchised minority than anything comparable since the 1970s.

Abu Bakr al-Baghdadi has been all of these, and now – after he was killed in a raid by US troops – he leaves behind a trail of ghastly crimes, internecine hatreds and the sad realization that he and his brand of bloodthirsty, loathing ISIS are an ongoing symptom of regional upheaval and failure, and of what the Internet can do to the isolated and deranged.

In its geographical scope, ISIS was the candle that burned twice as bright and burned half as long. It was in late 2013 that Baghdadi’s followers first swept into Raqqa. That began their ambitions in Syria, and led in June 2014 to the establishing of what they called an Islamic “caliphate,” never short of ambition, but rarely showing enough sobriety or statehood to last for very long.

They had rules, an army, and briefly a currency, yet just over three years later were reduced to fighting for scraps of Mosul in Iraq and the object of a large offensive against their de facto capital in Raqqa.

ISIS’ control of Mosul officially crumbled in July 2017, when Iraqi Prime Minster Haider al-Abadi declared that troops had recaptured the metropolis.

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Territorially, ISIS fell as fast as they rose, yet now the world must deal with the menacing tail-end of their worldview: those remaining followers who dream up acts of often cowardly terror that will later be claimed by ISIS as one of their own. The ideology lives on, and its message is Baghdadi’s hideous legacy on earth.

Baghdadi came as close to being in public as he ever would in July 2014, when he appeared in, and lectured to, a mosque in Mosul. Local reports suggested a huge convoy ferried him to the building – a sign at the time, perhaps, that US drones were inadequately prepared for their new quarry.

In Mosul he spoke at length, relishing his self-declared role – deeply offensive to most Muslims – as their new caliph. He said he was the Caliph Ibrahim, the self-anointed spiritual leader of a 1.6 billion-strong religion. What had happened to this diminutive scholar from Baghdad, in Iraq’s dusty plains and dense alleyways, to leave him capable of such a self-aggrandizing pronouncement and the sickening violence that went with it?

It is a question whose answer is more likely to be found in the crucible of violence-plagued, US-occupied Iraq than in the scant details that are known about Baghdadi’s personal beginnings.

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Jihadist websites and other sources suggest he was born in Diyala or Samarra in 1971 and went to the Islamic University in Baghdad, where he studied Islamic culture and jurisprudence to a Ph.D. level. The same jihadist biography gives his full name as “Ibrahim bin Awwad bin Ibrahim al-Badri al-Radhwi al-Husseini al-Samarrai.”

Reports suggest he may have been a cleric in a Samarra mosque until the American invasion in 2003. A year later, he was arrested during the Sunni insurgency that gripped Iraq and ferociously hampered the US occupation.

It was Iraq’s Sunnis for whom Baghdadi clearly felt aggrieved, and from where he would later draw support. Years of internecine sectarian violence had inflamed the Sunni-Shia tensions Saddam Hussein had so ruthlessly quashed, and provided a vengeful appetite for the kind of sectarian loathing ISIS would come to represent.

The jihadist biography – published in 2014 – claims Baghdadi spent the “last eight and a half years of fighting and hit-and-run strikes,” which might explain why he was found in the insurgency hotbed of Falluja, where he was detained in 2004.

Reports have suggested he was then held, for perhaps until 2009, under the name Ibrahim Awad Ibrahim Al Badry, in Camp Bucca – a US facility where other key future jihadist and ISIS leaders were incarcerated by the over-burdened and struggling American military.

Prison – as is often the truism – most likely changed him. On his emergence, the world next learned of Baghdadi as the leader of the Islamic State in Iraq, formerly known as al Qaeda in Iraq, the savage insurgency led by Abu Musab Al-Zarqawi until his death in a US bombing raid in 2006.

In 2010, the group was in disarray, after a lengthy brutal fight whose inhumane tactics had robbed them of some supporters. Baghdadi, then age 39, spurred a transformation by focusing on the enduring disenfranchisement felt by Iraq’s Sunnis.

The US had empowered a predominantly Shia clique of politicians, believing they would both fairly represent the Shia majority of Iraq that Saddam had repressed, but also give the Sunnis a continued voice in government. That didn’t happen, but what had taken its place were Shia death squads seeking revenge for Sunni insurgent attacks. A bloodbath ensued, one whose seemingly infinite sectarian hatred Baghdadi sought to harness.

Instability in Iraq and civil war in Syria were a gift to Baghdadi’s ambitions. The group got organized – extorting locals, robbing banks, aiming for ever larger attacks, and eventually declaring their caliphate. At the time the pronouncement seemed partially ridiculous to observers: no insurgent group could take and hold territory in the chaos and gunpowder of Syria’s conflict. But the caliphate grew, in size and confidence.

Baghdadi himself is thought to have authorized the gruesome execution of American journalist James Foley, whose lurid video provoked the Obama White House to take firmer military action against the group.

Thus began the world’s war with ISIS, a group that had become an umbrella mechanism for experienced foreign jihadists seeking a new path in the turmoil of Syria; veteran Iraq insurgents, some with Baathist era military experience; and even adventurous and slightly unhinged war-tourists, ensnared by the adrenaline rush of the combat videos so relentlessly pumped out at the public by Baghdadi’s prolific minister for information – the also deceased Abu Mohammed Adnani.

The group’s radical atavistic brutality made the Afghan Taliban at times appear moderate. ISIS beheaded people as if it were a leisure activity; threw gay men from rooftops; encouraged children not only to fight, but also execute adults at close range on video; and burned or drowned people alive in cages. Observing Baghdadi’s ISIS, it was easy to imagine that somewhere, some time, they sat in meetings imagining ways in which to out-do their latest, most gut-wrenching atrocity. They had become an experiment in the reaches of human cruelty, one that Baghdadi happily oversaw.

After his one Mosul tirade in 2014, Baghdadi vanished from view. A report in 2015 claimed he was badly wounded – even bedridden – by a US strike, yet the Pentagon never confirmed this injury. More reports suggested he was wounded again in 2017, as US-backed and other forces closed in on ISIS’ territory in Syria.

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In 2018, as ISIS faced repeated defeats and growing pressure from all sides, the group released an audio recording of Baghdadi, in which he admitted his militants were losing the battle for their self-declared state. He described the situation as a test from Allah and urged fighters to stick together. The following year, in another apparent attempt to rally the troops, ISIS released a video of Baghdadi, the first time he had been seen since that 2014 speech. In the video, a man purporting to be Baghdadi appeared to be wearing a casual outfit, sitting on the ground next to an assault rifle, he referenced contemporary events, including the deadly Easter Bombings in Sri Lanka, which ISIS claimed to have inspired.

Overt leadership was never Baghdadi’s lure. He did not direct operations in detail, or visibly lead fighters into battle. He allowed himself to be the overarching “spiritual” leader of an idea that spread like a virus on the internet whose attraction to young and deranged men as far away as Libya, Brussels and Paris was so strong that they would take the lives of others and their own just to be associated with it.

With Baghdadi’s death, the minimal understanding about how he became such a monster contributes to how little is known about what fuels and sparks ISIS’ sickness. Almost a decade since their first incarnation, the anger and cruelty that drives them remains hard for Western observers to fully grasp – leaving the group distant and its inner psyche elusive. Perhaps that is how Baghdadi wanted it.