By Jim Muir
17 October 2017
Abu Anis only realised something unusual was happening when he heard the sound of explosions coming from the old city on the western bank of the Tigris as it runs through Mosul.
"I phoned some friends over there, and they said armed groups had taken over, some of them foreign, some Iraqis," the computer technician said. "The gunmen told them, 'We've come to get rid of the Iraqi army, and to help you.'"
The following day, the attackers crossed the river and took the other half of the city. The Iraqi army and police, who vastly outnumbered their assailants, broke and fled, officers first, many of the soldiers stripping off their uniforms as they joined a flood of panicked civilians.
It was 10 June 2014, and Iraq's second biggest city, with a population of around two million, had just fallen to the militants of the group then calling itself Islamic State in Iraq and al-Sham/the Levant (Isis or Isil).
Four days earlier, black banners streaming, a few hundred of the Sunni militants had crossed the desert border in a cavalcade from their bases in eastern Syria and met little resistance as they moved towards their biggest prize.
Rich dividends were immediate. The Iraqi army, rebuilt, trained and equipped by the Americans since the US-led invasion of 2003, abandoned large quantities of armoured vehicles and advanced weaponry, eagerly seized by the militants. They also reportedly grabbed something like $500m from the Central Bank's Mosul branch.
"At the beginning, they behaved well," said Abu Anis. "They took down all the barricades the army had put up between quarters. People liked that. On their checkpoints they were friendly and helpful - 'Anything you need, we're here for you.'"
The Mosul honeymoon was to last a few weeks. But just down the road, terrible things were already happening.
As the Iraqi army collapsed throughout the north, the militants moved swiftly down the Tigris river valley. Towns and villages fell like skittles. Within a day they had captured the town of Baiji and its huge oil refinery, and moved on swiftly to seize Saddam Hussein's old hometown, Tikrit, a Sunni hotbed.
Just outside Tikrit is a big military base, taken over by the Americans in 2003 and renamed Camp Speicher after the first US casualty in the 1991 "Desert Storm" Gulf war against Iraq, a pilot called Scott Speicher, shot down over al-Anbar province in the west.
Camp Speicher, by now full of Iraqi military recruits, was surrounded by the Isis militants and surrendered. The thousands of captives were sorted, the Shia were weeded out, bound, and trucked away to be systematically shot dead in prepared trenches. Around 1,700 are believed to have been massacred in cold blood. The mass graves are still being exhumed.
Far from trying to cover up the atrocity, Isis revelled in it, posting on the internet videos and pictures showing the Shia prisoners being taken away and shot by the black-clad militants.
In terms of exultant cruelty and brutality, worse was not long in coming.
After a pause of just two months, Isis - now rebranded as "Islamic State" (IS) - erupted again, taking over large areas of northern Iraq controlled by the Kurds.
That included the town of Sinjar, mainly populated by the Yazidis, an ancient religious minority regarded by IS as heretics.
Hundreds of Yazidi men who failed to escape were simply killed. Women and children were separated and taken away as war booty, to be sold and bartered as chattels, and used as sex slaves. Thousands are still missing, enduring that fate.
Deliberately shocking, bloodthirsty exhibitionism reached a climax towards the end of the same month, August 2014.
In the following weeks, more American and British journalists and aid workers - Steven Sotloff, David Haines, Alan Henning, and Peter Kassig (who had converted to Islam and changed his name to Abdul Rahman) - appeared being slaughtered in similar, slickly produced videos, replete with propaganda statements and dire warnings.
In the space of a few months, IS had blasted its way from obscurity on to the centre of the world stage. Almost overnight, it became a household word.
Seven-and-a-half thousand miles (12,000km) away, then Australian Prime Minister Tony Abbott summed up the breathtaking novelty of the horror. It was, he said "medieval barbarism, perpetrated and spread with the most modern of technology".
IS had arrived, and the world was taking notice. But the men in black did not appear out of the blue. They had been a long time coming.
The Theology of Murder
The ideological or religious roots of IS and like-minded groups go deep into history, almost to the beginning of Islam itself in the 7th Century AD.
Like Christianity six centuries before it, and Judaism some eight centuries before that, Islam was born into the harsh, tribal world of the Middle East.
"The original texts, the Old Testament and the Quran, reflected primitive tribal Jewish and Arab societies, and the codes they set forth were severe," writes the historian and author William Polk.
"They aimed, in the Old Testament, at preserving and enhancing tribal cohesion and power and, in the Koran, at destroying the vestiges of pagan belief and practice. Neither early Judaism nor Islam allowed deviation. Both were authoritarian theocracies."
As history moved on, Islam spread over a vast region, encountering and adjusting to numerous other societies, faiths and cultures. Inevitably in practice it mutated in different ways, often becoming more pragmatic and indulgent, often given second place to the demands of power and politics and temporal rulers.
For hard-line Muslim traditionalists this amounted to deviationism, and from early on, there was a clash of ideas in which those arguing for a strict return to the "purity" of the early days of Islam often paid a price.
The eminent scholar Ahmad ibn Hanbal (780-855), who founded one of the main schools of Sunni Islamic jurisprudence, was jailed and once flogged unconscious in a dispute with the Abbasid caliph in Baghdad. Nearly five centuries later, another supreme theologian of the same strict orthodox school, Ibn Taymiyya, died in prison in Damascus.
These two men are seen as the spiritual forefathers of later thinkers and movements which became known as "Salafist", advocating a return to the ways of the first Muslim ancestors, the Salaf Al-Salih (righteous ancestors).
They inspired a later figure whose thinking and writings were to have a huge and continuing impact on the region and on the Salafist movement, one form of which, Wahhabism, took his name.
Muhammad ibn Abd al-Wahhab was born in 1703 in a small village in the Nejd region in the middle of the Arabian peninsula.
A devout Islamic scholar, he espoused and developed the most puritanical and strict version of what he saw as the original faith, and sought to spread it by entering pacts with the holders of political and military power.
In an early foray in that direction, his first action was to destroy the tomb of Zayd ibn al-Khattab, one of the Companions of the Prophet Muhammad, on the grounds that by the austere doctrine of Salafist theology, the veneration of tombs constitutes shirk, the revering of something or someone other than Allah.
But it was in 1744 that Abd al-Wahhab made his crucial alliance with the local ruler, Muhammad ibn Saud. It was a pact whereby Wahhabism provided the spiritual or ideological dimension for Saudi political and military expansion, to the benefit of both.
Passing through several mutations, that dual alliance took over most of the peninsula and has endured to this day, with the House of Saud ruling in sometimes uneasy concert with an ultra-conservative Wahhabi religious establishment.
The entrenchment of Wahhabi Salafism in Saudi Arabia - and the billions of petrodollars to which it gained access - provided one of the wellsprings for jihadist militancy in the region in modern times. Jihad means struggle on the path of Allah, which can mean many kinds of personal struggle, but more often is taken to mean waging holy war.
But the man most widely credited, or blamed, for bringing Salafism into the 20th Century was the Egyptian thinker Sayyid Qutb. He provided a direct bridge from the thought and heritage of Abd al-Wahhab and his predecessors to a new generation of jihadist militants, leading up to al-Qaeda and all that was to follow.
Born in a small village in Upper Egypt in 1906, Sayyid Qutb found himself at odds with the way Islam was being taught and managed around him. Far from converting him to the ways of the West, a two-year study period in the US in the late 1940s left him disgusted at what he judged unbridled godless materialism and debauchery, and his fundamentalist Islamic outlook was honed harder.
Back in Egypt, he developed the view that the West was imposing its control directly or indirectly over the region in the wake of the Ottoman Empire's collapse after World War One, with the collaboration of local rulers who might claim to be Muslims, but who had in fact deviated so far from the right path that they should no longer be considered such.
For Qutb, offensive jihad against both the West and its local agents was the only way for the Muslim world to redeem itself. In essence, this was a kind of Takfir - branding another Muslim an apostate or Kafir (infidel), making it justified and even obligatory and meritorious to kill him.
Although he was a theorist and intellectual rather than an active jihadist, Qutb was judged dangerously subversive by the Egyptian authorities. He was hanged in 1966 on charges of involvement in a Muslim Brotherhood plot to assassinate the nationalist President, Gamal Abdel Nasser.
Qutb was before his time, but his ideas lived on in the 24 books he wrote, which have been read by tens of millions, and in the personal contact he had with the circles of people like Ayman al-Zawahiri, another Egyptian who is the current al-Qaeda leader.
Another intimate of the al-Qaeda founder Osama Bin Laden said: "Qutb was the one who most affected our generation." He has also been described as "the source of all jihadist thought", and "the philosopher of the Islamic revolution".
More than 35 years after he was hanged, the official commission of inquiry into al-Qaeda's 9/11 attack on the Twin Towers in 2001 concluded: "Bin Laden shares Qutb's stark view, permitting him and his followers to rationalise even unprovoked mass murder as righteous defence of an embattled faith."
And his influence lingers on today. Summing up the roots of IS and its predecessors, the Iraqi expert on Islamist movements Hisham al-Hashemi said: "They are founded on two things: a Takfiri faith based on the writings of Muhammad ibn Abd al-Wahhab, and as methodology, the way of Sayyid Qutb."
The theology of militant Jihadism was in place. But to flourish, it needed two things - a battlefield, and strategists to shape the battle.
Afghanistan was to provide the opportunity for both.
Rise of al-Qaeda
The Soviet invasion in 1979, and the 10 years of occupation that followed, provided a magnet for would-be jihadists from around the Arab world. Some 35,000 of them flocked to Afghanistan during that period, to join the jihad and help the mainly Islamist Afghan Mujahideen guerrillas turn the country into Russia's Vietnam.
There is little evidence that the "Afghan Arabs", as they became known, played a pivotal combat role in driving the Soviets out. But they made a major contribution in setting up support networks in Pakistan, channelling funds from Saudi Arabia and other donors, and funding schools and militant training camps. It was a fantastic opportunity for networking and forging enduring relationships as well as tasting jihad first hand.
Ironically, they found themselves on the same team as the Americans. The CIA's Operation Cyclone channelled hundreds of millions of dollars through Pakistan to militant Afghan mujahedeen leaders such as Golbuddin Hekmatyar, who associated closely with the Arab jihadists.
It was in Afghanistan that virtually all the major figures in the new jihadist world cut their teeth. They helped shape events there in the aftermath of the Soviet withdrawal in 1989, a period that saw the emergence of al-Qaeda as a vehicle for a wider global jihad, and Afghanistan provided a base for it.
By the time the Taliban took over in 1996, they were virtually in partnership with Osama Bin Laden and his men, and it was from there that al-Qaeda launched its fateful 9/11 attack in 2001.
The formative Afghan experience provided both the combat-hardened Salafist jihadist leaders and the strategists who were to play an instrumental role in the emergence of the IS of today.
Most significant was the Jordanian jihadist Abu Musab al-Zarqawi, who more than anybody else ended up being the direct parent of IS in almost every way.
A high-school dropout whose prison career began with a sentence for drug and sexual offences, Zarqawi found religion after being sent to classes at a mosque in the Jordanian capital, Amman. He arrived in Pakistan to join jihad in Afghanistan just in time to see the Soviets withdraw in 1989, but stayed on to work with jihadists.
After a stint back in Jordan where he received a 15-year jail sentence on terrorist charges but was later released in a general amnesty, Zarqawi finally met Bin Laden and Ayman al-Zawahiri in 1999. By all accounts the two al-Qaeda leaders did not take to him. They found him brash and headstrong, and they did not like the many tattoos from his previous life that he had not been able to erase.
But he was charismatic and dynamic, and although he did not join al-Qaeda, they eventually put him in charge of a training camp in Herat, western Afghanistan. It was here that he worked with an ideologue whose radical writings became the scriptures governing subsequent Salafist blood-letting: Abu Abdullah al-Muhajir.
"The brutality of beheading is intended, even delightful to God and His Prophet," wrote Muhajir in his book The Theology of Jihad, more generally referred to as the Theology of Bloodshed. His writings provided religious cover for the most brutal excesses, and also for the killing of Shia as infidels, and their Sunni collaborators as apostates.
The other book that has been seen as the virtual manual - even the Mein Kampf - for IS and its forebears is The Management of Savagery, by Abu Bakr Naji, which appeared on the internet in 2004.
"We need to massacre and to do just as has been done to Banu Qurayza, so we must adopt a ruthless policy in which hostages are brutally and graphically murdered unless our demands are met," Naji wrote. He was referring to a Jewish tribe in seventh-century Arabia which reportedly met the same fate at the hands of early Muslims as the Yazidis of Sinjar did nearly 14 centuries later: the men were slaughtered, the women and children enslaved.
Naji's sanctioning of exemplary brutality was part of a much wider strategy to prepare the way for an Islamic caliphate. Based partly on the lessons of Afghanistan, his book is a detailed blueprint for provoking the West into interventions which would further rally the Muslims to jihad, leading to the ultimate collapse of the enemy.
The scenario is not so fanciful if you consider that the Soviet Union went to pieces barely two years after its withdrawal from Afghanistan.
Naji is reported to have been killed in a US drone strike in Pakistan's Waziristan province in 2008.
The fallout from the 9/11 attacks changed things radically for the jihadists in late 2001. The US and allies bombed and invaded Afghanistan, ousting the Taliban, and launching a wider "War on Terror" against al-Qaeda.
Bin Laden went underground, and Zarqawi and others fled. The dispersing militants, fired up, badly needed another battlefield on which to provoke and confront their Western enemies.
Luck was on their side. The Americans and their allies were not long in providing it.
Their invasion of Iraq in the spring of 2003 was, it turned out, entirely unjustified on its own chosen grounds - Saddam Hussein's alleged production of weapons of mass destruction, and his supposed support for international terrorists, neither of which was true.
By breaking up every state and security structure and sending thousands of disgruntled Sunni soldiers and officials home, they created precisely the state of "savagery", or violent chaos, that Abu Bakr Naji envisaged for the jihadists to thrive in.
Iraq was on the way to becoming what US officials came to call the "parent tumour" of the IS presence in the region.
Under Saddam's tightly-controlled Baath Party regime, the Sunnis enjoyed pride of place over the majority Shia, who have strong ties with their co-religionists across the border in Iran.
The US-led intervention disempowered the Sunnis, creating massive resentment and providing fertile ground for the outside Salafist jihadists to take root in.
They were not long in spotting their constituency. Abu Musab Zarqawi moved in, and within a matter of months was organising deadly, brutal and provocative attacks aimed both at Western targets and at the majority Shia community.
Doctrinal differences between the two sects go back to disputes over the succession to the Prophet Muhammad in the early decades of Islam, but conflict between them is generally based on community, history and sectarian politics rather than religion as such.
Setting himself up with a new group called Tawhid wa al-Jihad (Tawhid means declaring the uniqueness of Allah), Zarqawi immediately forged a pragmatic operational alliance with underground cells of the remnants of Saddam's regime, providing the two main intertwined strands of the Sunni-based insurgency: militant Jihadism, and Iraqi Sunni nationalism with Baathist organisation at its core.
His group claimed responsibility for several deadly attacks in August 2003 that set the pattern for much of what was to come: a suicide truck bomb explosion at the UN headquarters in Baghdad that killed the envoy Sergio Vieira de Mello and 20 of his staff, and a suicide car bomb blast in Najaf which killed the influential Shia ayatollah Muhammad Baqir al-Hakim and 80 of his followers. The bombers were Salafist jihadists, but logistics were reportedly provided by underground Baathists.
The following year, Zarqawi himself was believed by the CIA to be the masked killer shown in a video beheading an American hostage, Nicholas Berg, in revenge for the Abu Ghraib prison abuses of Iraqi detainees by members of the US military.
As the battle with the Americans and the new Shia-dominated Iraqi government intensified, Zarqawi finally took the oath of loyalty to Bin Laden, and his group became the official al-Qaeda branch in Iraq.
But they were never really on the same page. Zarqawi's provocative attacks on Shia mosques and markets, triggering sectarian carnage, and his penchant for publicising graphic brutality, were all in line with the radical teachings he had imbibed. But they drew rebukes from the al-Qaeda leadership, concerned at the impact on Muslim opinion.
Zarqawi paid little heed. His strain of harsh radicalism passed to his successors after he was killed by a US air strike in June 2006 on his hideout north of Baghdad. He was easily identified by the tattoos he had never managed to get rid of.
The direct predecessor of IS emerged just a few months later, with the announcement of the Islamic State in Iraq (ISI) as an umbrella bringing the al-Qaeda branch together with other insurgent factions.
But tough times lay ahead. In January 2007, the Americans began "surging" their own troops in Iraq from 132,000 to a peak of 168,000, adopting a much more hands-on approach in mentoring the rebuilt Iraqi army. At the same time, they enticed Sunni tribes in western al-Anbar province to stop supporting the jihadists and join the US-led Coalition-Iraqi government drive to quell the insurgency, which many did, on promises that they would be given jobs and control over their own security.
By the time both the new ISI and al-Qaeda leaders were killed in a US-Iraqi army raid on their hideout in April 2010, the insurgency was at its lowest ebb, pushed back into remote corners of Sunni Iraq.
They were both replaced by one man, about whom very little was publicly known at the time, and not much more since: Ibrahim Awad al-Badri, better known by his nom de guerre, Abu Bakr al-Baghdadi.
Six eventful years later, he would be proclaimed Caliph Ibrahim, Commander of the Faithful and leader of the newly declared "Islamic State".
Baghdadi's career is so shrouded in mist that there are very few elements of it that can be regarded as fact. By all accounts he was born near Samarra, north of Baghdad, so the epithet "Baghdadi" seems to have been adopted to give him a more national image, while "Abu Bakr" evokes the first successor to (and father-in-law of) Prophet Muhammad.
Like the original Abu Bakr, Baghdadi is also reputed to come from the Prophet's Quraysh clan. That, and his youth - born in 1971 - may have been factors in his selection as leader.
All accounts of his early life agree that he was a quiet, scholarly and devout student of Islam, taking a doctorate at the Islamic University of Baghdad. Some even say he was shy, and a bit of a loner, living for 10 years in a room beside a small Sunni mosque in western Baghdad.
The word "charismatic" has never been attached to him.
Who The Leader Is Of IS?
But by the time of the US-led invasion in 2003, he appears to have become involved with a militant Sunni group, heading its Sharia (Islamic law) committee. American troops detained him, and he was reportedly held in the detention centre at Camp Bucca in the south for most of 2004.
Camp Bucca (named after a fireman who died in the 9/11 attacks) housed up to 20,000 inmates and became a university from which many IS and other militant leaders graduated. It gave them an unrivalled opportunity to imbibe and spread radical ideologies and sabotage skills and develop important contacts and networks, all in complete safety, under the noses and protection of their enemies.
Baghdadi would also certainly have met in Camp Bucca many of the ex-Baathist military commanders with whom he was to form such a deadly partnership.
The low-profile, self-effacing Baghdadi rang no alarm bells with the Americans. They released him, having decided he was low-risk.
But he went on to work his way steadily up through the insurgent hierarchy, virtually unknown to the Iraqi public.
By the time Baghdadi took over in 2010, the curtains seemed to be coming down for the jihadists in the Iraqi field of "savagery".
But another one miraculously opened up for them across the border in neighbouring Syria at just the right moment. In the spring of 2011, the outbreak of civil war there offered a promising new arena of struggle and expansion. The majority Sunnis were in revolt against the oppressive regime of Bashar al-Assad, dominated by his Alawite minority, an offshoot of Shia Islam.
Baghdadi sent his men in. By December 2011, deadly car bombs were exploding in Damascus which turned out to be the work of the then shadowy al-Nusra Front. It announced itself as an al-Qaeda affiliate the following month. It was headed by a Syrian jihadist, Abu Mohammed al-Jawlani. He had been sent by Baghdadi, but had his own ideas.
Jostling with a huge array of competing rebel groups in Syria, al-Nusra won considerable support on the ground because of its fearless and effective fighting skills, and the flow of funds and foreign fighters that support from al-Qaeda stimulated. It was relatively moderate in its Salafist approach, and cultivated local relationships.
Al-Nusra was slipping out of Baghdadi's control, and he didn't like it. In April 2013, he tried to rein it back, announcing that al-Nusra was under his command in a new Islamic State in Iraq and al-Sham (Syria or the Levant). Isis, or Isil, was born.
What's In A Name?
During the short and turbulent period over which it has imposed itself as a major news brand, so-called Islamic State has confused the world with a series of name changes reflecting its mutations and changing aspirations, leaving a situation where there is no universal agreement on how to refer to it.
After emerging in Iraq as the Islamic State in Iraq (ISI), its spread to Syria prompted the addition of "and al-Sham", a word that can mean Damascus, Syria, or the wider Levant
Many chose to use the easy acronym Isis, with the "S" standing either for Syria or al-Sham, though the US administration and others opted for Isil (the "l" standing for "Levant"). Both are still widely used though technically outdated
In Arabic the same acronym can come out as Daash, sometimes spelled Daesh in English; it has passed into common usage among many Arabs, but is disliked by the organisation itself, which sees it as disrespectful of the "state"; although Daash has no meaning in Arabic, it also has an unpleasant sound to it, which may be why American and Western officialdom often use it
After further expansion of territory and ambitions, the movement dropped geographical specificity and called itself simply "the Islamic State"; Much of the world was politically reluctant simply to call it that, for fear of implying legitimacy
The BBC and others have generally opted for calling it the "self-styled" or "so-called" Islamic State on first reference, and IS thereafter
But Jawlani rebelled, and renewed his oath of loyalty to al-Qaeda's global leadership, now under Ayman al-Zawahiri following Bin Laden's death in 2011. Zawahiri ordered Baghdadi to go back to being just the Islamic State in Iraq (ISI) and leave al-Nusra as the al-Qaeda Syria franchise.
It was Baghdadi's turn to ignore orders from head office.
Before 2013 was out, Isis and al-Nusra were at each other's throats. Hundreds were killed in vicious internecine clashes which ended with Isis being driven out of most of north-west Syria by al-Nusra and allied Syrian rebel factions. But Isis took over Raqqa, a provincial capital in the north-east, and made it its capital. Many of the foreign jihadists who had joined al-Nusra also went over to Isis, seeing it as tougher and more radical. In early 2014, al-Qaeda formally disowned Isis.
Isis had shaken off the parental shackles. But it had lost a lot of ground, and was bottled up. One of its main slogans, Remaining and Expanding, risked becoming empty. So where next?
Fortune smiled once more. Back in Iraq, conditions had again become ripe for the jihadists. The Americans had gone, since the end of 2011. Sunni areas were again aflame and in revolt, enraged by the sectarian policies of the Shia Prime Minister, Nouri Maliki. Sunnis felt marginalised, oppressed and angry.
When Isis decided to move, it was pushing at an open door. In fact, it had never really left Iraq, just gone into the woodwork. As it swept through Sunni towns, cities and villages with bewildering speed in June 2014, sleeper cells of Salafist jihadists and ex-Saddamist militants and other sympathisers broke cover and joined the takeover.
With the capture of Mosul, Isis morphed swiftly into a new mode of being, like a rocket jettisoning its carrier. No longer just a shadowy terrorist group, it was suddenly a jihadist army holding large stretches of territory, ruling millions of people, and not only threatening the Iraqi state, but challenging the entire world.
The change was signalled on 29 June by the proclamation of the "Islamic State", replacing all previous incarnations, and the establishment of the "caliphate". A few days later, the newly anointed Caliph Ibrahim, aka Abu Bakr al-Baghdadi, made a surprise appearance in Mosul in the pulpit of the historic Grand Mosque of al-Nuri, heavily laden with anti-Crusader associations. He called on the world's Muslims to rally behind him.
By declaring a caliphate and adopting the generic "Islamic State" title, the organisation was clearly setting its sights far beyond Syria and Iraq. It was going global.
Announcing a caliphate has huge significance and resonance within Islam. While it remains the ideal, Bin Laden and other al-Qaeda leaders had always shied away from it, for fear of failure. Now Baghdadi was trumping the parent organisation, setting IS up in direct competition with it for the leadership of global Jihadism.
A caliphate (Khilafah) is the rule or rein of a caliph (Khalifa), a word which simply means a successor - primarily of the Prophet Muhammad. Under the first four caliphs who followed after he died in 632, the Islamic Caliphate burst out of Arabia and extended through modern-day Iran to the east, into Libya to the west, and to the Caucasus in the north.
The Umayyad caliphate which followed, based in Damascus, took over almost all of the lands that IS would like to control, including Spain. The Baghdad-based Abbasid caliphate took over in 750 and saw a flowering of science and culture, but found it hard to hold it all together, and Baghdad was sacked by the Mongols in 1258.
Emerging from that, the Ottoman Empire, based in Constantinople (Istanbul), stretched almost to Vienna at its peak, and was also a caliphate, though the distinction with empire was often blurred. The caliphate was finally abolished by Ataturk in 1924.
So when Baghdadi was declared Caliph of the Islamic State, it was an act of extraordinary ambition. He was claiming no less than the mantle of the Prophet, and of his followers who carried Islam into vast new realms of conquest and expansion.
For most Islamic scholars and authorities, not to mention Arab and Muslim leaders, such claims from the chief of one violent extremist faction had no legitimacy at all, and there was no great rush to embrace the new caliphate. But the millennial echoes it evoked did strike a chord with some Islamic romantics - and with some like-minded radical groups abroad.
Four months after the proclamation, a group of militants in Libya became the first to join up by pledging allegiance to Baghdadi, followed a month later by the Ansar Beit al-Maqdis jihadist faction in Egypt's Sinai. IS's tentacles spread deeper into Africa in March 2015 when Boko Haram in Nigeria took the oath of loyalty. Within a year, IS had branches or affiliates in 11 countries, though it held territory in only five, including Iraq and Syria.
It was in those two core countries that Baghdadi and his followers started implementing their state project on the ground, applying their own harsh vision of Islamic rule.
To the outside world, deprived of direct access to the areas controlled by IS, one of the most obvious and shocking aspects of this was their systematic destruction of ancient cultural and archaeological heritage sites and artefacts.
Some of the region's best-known and most-visited sites were devastated, including the magnificent temples of Bel and Baalshamin at Palmyra in Syria, and the Assyrian cities of Hatra and Nimrud in Iraq.
It wasn't just famous archaeological sites that came under attack. Christian churches and ancient monasteries, Shia mosques and shrines, and anything depicting figures of any sort were destroyed, and embellishments removed even from Sunni mosques. Barely a month after taking over Mosul, IS demolition squads levelled the 13th Century shrine of the Imam Awn al-Din, which had survived the Mongol invasion.
All of this was absolutely in line with IS's puritanical vision of Islam, under which any pictorial representation or shrine is revering something other than Allah, and any non-Muslim structures are monuments of idolatry. Even Saudi kings and princes to this day are buried without coffins in unmarked graves.
By posting videos of many of these acts which the rest of the world saw as criminal cultural vandalism, IS also undoubtedly intended to shock. In that sense, it was the cultural equivalent of beheading aid workers.
And there was a more practical and profitable side to the onslaught on cultural heritage. In highly organised manner, IS's Treasury Department issued printed permits to loot archaeological sites, and took a percentage of the proceeds.
That was just the tip of the iceberg of a complex structure of governance and control put in place as IS gradually settled into its conquests, penetrating into every aspect of people's lives in exactly the same way as Saddam Hussein's intelligence apparatus had done.
Captured documents published by Der Spiegel in 2015 give some idea of the role of ex-Baathist regime men in setting up and running IS in a highly structured and organised way, with much emphasis on intelligence and security.
Residents of Sunni strongholds like Mosul and Falluja in Iraq, and Raqqa in Syria, found that IS operatives already knew almost everything about everybody when they moved in and took over in 2014.
At checkpoints, ID cards were checked against databases on laptops, obtained from government ration or employee registers. Former members of the security forces had to go to specific mosques to "repent", hand over their weapons and receive a discharge paper.
"At first, all they did was change the preachers in the mosques to people with their own views," said a Mosul resident who fled a year later.
"But then they began to crack down. Women who had been able to go bare-headed now had to cover up, first with the headscarf and then with the full face-veil. Men have to grow beards and wear short-legged trousers. Cigarettes, hubble-bubble, music and cafes were banned, then satellite TV and mobile phones. Morals police [hisba] vehicles would cruise round, looking for offenders."
A Falluja resident recounted the story of a taxi-driver who had picked up a middle-aged woman not wearing a headscarf. They were stopped at an IS checkpoint, the woman given a veil and allowed to go, while the driver was sent to an Islamic court, and sentenced to two months' detention and to memorise a portion of the Koran. If you fail to memorise, the sentence is repeated.
"They have courts with judges, officials, records and files, and there are fixed penalties for each crime, it's not random," said the Falluja resident, speaking when IS still controlled the city. "Adulterers are stoned to death. Thieves have their hands cut off. Gays are executed by being thrown off high buildings. Informers are shot dead, Shia militia prisoners are beheaded."
Severed Heads on Park Fences: A Diary of Life under IS
An activist based in Raqqa from a group called Al-Sharqiya 24 has been keeping a diary of what life is like under Islamic State group rule.
Life under 'Islamic State': Diaries
IS departments carried the organisation's grip into every corner of life, including finance, agriculture, education, transport, health, welfare and utilities.
School curricula were overhauled in line with IS precepts, with history rewritten, all images being removed from schoolbooks and English taken off the menu.
"One thing you can say is this," said the Mosul resident after IS took over. "There is absolutely no corruption, no wasta [knowing the right people and pulling strings]. They are totally convinced they are on the right track."
One story tells a lot about IS and its ways.
As Iraqi security forces were pressing forward in areas around Ramadi in early 2016, civilians were fleeing the battle - and ARE fighters, losing the day, were trying to sneak out too.
Two women, running from the combat zone, approached a police checkpoint.
As they were being waved through to safety, one of the women suddenly turned to the police, pointed at the other, and said: "This is not a woman. He's an IS emir [commander]."
The police investigated, and it was true. The other woman was a man, who had shaved, and put on makeup and women's clothes. He turned out to be top of the list of wanted local IS commanders.
"When IS arrived, he killed my husband, who was a policeman, raped me, and then took me as his wife," the woman told the police.
"I put up with him all this time, waiting to avenge my husband and my honour," she said. "I tricked him into shaving and putting on makeup, then denounced him to the police."
How Does IS Treat Women?
"Nour" is a woman from Raqqa, the so-called Islamic State's (IS) former capital inside Syria. She managed to escape the city and became a refugee in Europe, where she met up with the BBC.
This story is based on her experiences and those of her two sisters, who were still inside the city when it was held by IS.
Taking On the World
Having taken over vast swathes of territory in Iraq with their lightning offensive in June 2014, the militants might have been expected to calm down and consolidate their gains.
But, like a shark that has to keep moving or else it will die, IS barely paused before initiating a new spiral of provocation and reprisals that was predictably to draw it into active conflict with almost all the major world powers.
Already, the June offensive had threatened the approaches to Baghdad, prompting the Americans to start bringing in hundreds of military advisers and trainers to see how to help the struggling Iraqi army.
Just two months later, the attack on Kurdish areas in the north triggered US air strikes in defence of the Kurdistan capital, Irbil, and then to help stave off the threat of genocide to the Yazidis. Fourteen other nations were to join the air campaign.
Ten days later, IS beheaded James Foley and the others followed, in line with the doctrine of exemplary brutality as punishment, deterrent and provocation. The most shocking was to come some months later, with the burning alive of the downed Jordanian pilot Moaz al-Kasasbeh. Shock intended.
The US-led bombing campaign was extended to Syria in September 2014 after IS besieged the Kurdish-held town of Kobane on the Turkish border. Coalition air strikes turned the tide there. IS lost hundreds of fighters killed at Kobane and elsewhere. More revenge was called for. IS turned abroad.
In the three years following the declaration of the "caliphate" in 2014, at least 150 attacks in 29 countries across the globe were either carried out or inspired by IS, with well over 2,000 victims killed.
The attacks carried the same message of punishment, deterrence and provocation as the hostage beheadings, while also demonstrating IS's global reach.
At the same time, they carried through the militants' doctrine of distracting the enemy by setting fires in different locations and making him squander resources on security. For IS, "the enemy" is everybody who does not embrace it. The world is divided into Dawlat al-Islam, the State of Islam, and Dawlat al-Kufr, the State of Unbelief.
The most consequential of these atrocities were the downing of a Russian airliner over Sinai on 31 October 2015 and the Paris attacks on 13 November, provoking both Russia and France to intensify air strikes on IS targets in Syria.
The lone-wolf massacre at a gay club in Orlando, Florida, on 12 June 2016, while apparently inspired rather than organised by IS, would undoubtedly further stiffen the US's already steely resolve to finish the organisation.
Had IS gone mad? It seemed determined to take on the whole world. It was goading and confronting the Americans, the Russians, and a long list of others. By its own count, it had a mere 40,000 fighters at its command (other estimates went as low as half that).
Could it really challenge the global powers and hope to survive? Or would President Barack Obama and his successor Donald Trump be able to fulfil Mr Obama's pledge to "degrade and ultimately destroy" the organisation?
If there seemed to be something apocalyptic about IS's "bring it on" defiance, that's because there was.
When the organisation first brought out its online magazine - a major showcase and recruitment tool - just a month after the "caliphate" was declared, it was not by chance that it was named Dabiq.
A small town north of Aleppo in Syria, Dabiq is mentioned in a Hadith (a reported saying of the Prophet Muhammad) in connection with Armageddon. In IS mythology, it is the scene where a cataclysmic showdown will take place between the Muslims and the infidels, leading to the end of days. Each issue of Dabiq begins with a quote from Abu Musab Zarqawi: "The spark has been lit here in Iraq, and its heat will continue to intensify - by Allah's permission - until it burns the crusader armies in Dabiq."
The prospect of taking part in that final glorious climax, achieving martyrdom on the path of Allah and an assured place in paradise, is one of the thoughts inspiring those heeding the IS call to jihad.
That could help explain why the organisation seemed to enjoy an endless supply of recruits willing to blow themselves to pieces in suicide attacks, which it calls "martyrdom-seeking operations" (suicide is forbidden in Islam). Hundreds have died in this way, and they happen virtually daily.
It's been one of the elements that made IS a formidable fighting force hard to destroy even in strictly military terms.
The Baathist Legacy At The Core Of IS
IS is in many respects a project of former Iraqi President Saddam Hussein's outlawed Baath party, but now with a different ideology. Former agents or officers of Saddam Hussein's regime dominate its leadership... They represent a battle-hardened and state-educated core that would likely endure (as they have done through US occupation and a decade of war) even if the organisation's middle and lower cadres are decimated.
What Made IS So Formidable?
The head of security and intelligence for the Kurdistan Regional Government (KRG) in northern Iraq, Masrour Barzani, tells the story of a frustrated would-be suicide bomber who screamed at his captors: "I was just 10 minutes away from being united with the Prophet Muhammad!"
"They think they're winners regardless of whether they kill you or they get killed," says Barzani. "If they kill you, they win a battle. If they get killed, they go to heaven. With people like this, it's very difficult to deter them from coming at you. So really the only way to defeat them is to eliminate them."
Probably for the first time in military history since the Japanese kamikaze squadrons of World War Two, suicide bombers are used by IS not only for occasional terrorist spectaculars, but as a standard and common battlefield tactic.
Virtually all IS attacks begin with one or several suicide bombers driving explosives-rigged cars or trucks at the target, softening it up for combat squads to go in. So much so that the "martyrdom-seekers" have been called the organisation's "air force", since they serve a similar purpose.
Formidable though that is, IS as a fighting force is much more than a bunch of wild-eyed fanatics eager to blow themselves up. For that, they have Saddam Hussein to thank.
"The core of IS are former Saddam-era army and intelligence officers, particularly from the Republican Guard," said an international intelligence official. "They are very good at moving their people around, resupply and so on, they're actually much more effective and efficient than the Iraqi army are. That's the hand of former military staff officers who know their business."
"They are very professional," adds Masrour Barzani. "They use artillery, armoured vehicles, heavy machinery etc, and they are using it very well. They have officers who know conventional war and how to plan, how to attack, how to defend. They really are operating on the level of a very organised conventional force. Otherwise they'd be no more than a terrorist organisation."
The partnership with the ex-Baathists, going back to Zarqawi's early days in Iraq, was clearly a vital component in IS success.
But that did not mean its fighters were invincible on the battlefield, even in the early days of stunningly rapid expansion. The Kurds in north-east Syria were fighting IS off with no outside help for a year before anybody noticed. And even now, IS makes what would conventionally be seen as costly mistakes.
10 Million People Lived Under IS In Syria And Iraq
In December 2015, for example, they lost several hundred fighters in one abortive attack east of Mosul alone, and probably 2,500 altogether that month alone. Pentagon officials said coalition air strikes killed some 50,000 IS militants in Iraq and Syria between August 2014 and the end of 2016.
But IS initially seemed to have little difficulty making up the numbers. With a population of perhaps 10 million acquiescent Sunnis to draw on, in Iraq and Syria, most recruiting was done locally. Clearly, had it remained in place, there would soon have been a new generation of young militants drawn from local sources.
"I didn't join out of conviction," says Bakr Madloul, a 24-year-old bachelor who was arrested in December at his home in a Sunni quarter in southern Baghdad and accused of taking part in deadly IS car bomb attacks on mainly Shia areas, which he admits.
Bakr says he was working as a construction foreman in Kurdistan when IS took over Mosul. He was detained for questioning by Kurdish security, and met a militant in jail who persuaded him to go to Mosul, where he joined up with IS and manned a checkpoint until it was hit by a Coalition air strike.
He was then sent back to his Baghdad suburb to help organise car bombings. The explosives-packed vehicles were sent from outside Baghdad, and his job was to place them where he was told by his controller, usually in crowded streets or markets.
"Only one of the five car bombs I handled was driven by a suicide bomber," he says. "I spoke to him. He was 22 years old, an Iraqi. He believed he would go to paradise when he died. It's the easiest and quickest way to Heaven. They strongly believe this. They would blow themselves up to get to Heaven. There were older ones in their 30s and 40s."
"I asked my controllers more than once, 'Is it OK to kill women and children?' They would answer, 'They're all the same.' But to me, killing women and children, I didn't feel at all comfortable about that. But once you're in, you're stuck. If you try to leave, they call you a Murtad, an apostate, and they'll kill you or your family."
Bakr knows he will almost certainly hang. Since we spoke, he has in fact been given two death sentences. I asked him if he would do the same things over if he had his life again. He laughed.
"Absolutely not. I would get out of Iraq, away from IS, away from the security forces. I took this path without realising the consequences. There is no way back. I see that now."
But up in Kurdistan, another IS prisoner, Muhannad Ibrahim, has no such regrets.
A 32-year-old from a village near Mosul with a wife and three children, he was a construction worker for a Turkish company when IS took over the city. Two of his older brothers had died fighting the Americans there in 2004 and 2006. He joined IS without hesitation and was commanding a small detachment when he was captured in a battle with the Kurds.
"We were being oppressed by the Shia, they were always insulting and bothering us," he says. "But that's not the main motivation, religious conviction is more important. All my family is religious, praise be to Allah. I came to IS through my faith and religious principles."
"If I had my time over again, I would take the same path, the same choices. Because I am convinced by this thing, I have to go to the end. Either I am killed, or Allah will decree some other fate for me."