Territorial takeover
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 is the leader of IS?

As a youth, Baghdadi had a passion for Koranic recitation and was meticulous in his observance of religious law. His family nicknamed him The Believer because he would chastise his relatives for failing to live up to his stringent standards.

Who is Islamic State leader Abu Bakr al-Baghdadi?
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-Julani. 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 Julani 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 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 Nour al-Din al-Zangi, 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 (khilafa) 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 issues printed permits to loot archaeological sites, and takes a percentage of the proceeds.

That is 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 last year 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. "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."

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.