The world's most potent terror group is also its most savvy. In its 18 month existence, Islamic State (Isis) has imposed its old world view of Islam using very modern means. Slick production, an eye for a camera angle and high definition horror have done just as much to showcase the group – and further its aims – as its rampage across Iraq and Syria.

Almost every move Isis has made has been chronicled in some form, either through shaky hand held mobile phones that have captured battle scenes Blair Witch style, or by applying more sophisticated Hollywood production values.

An hour-long chronology of barbarism that the group posted online in June featured an opening sequence copied straight from the 2009 film about the Iraq war, The Hurt Locker. Isis may eschew much of the modern world, but it certainly studies its enemy. And, in what is the biggest punt of its short and bloody life, the group appears to have gambled that it can call the bluff of its most formidable foe.

On extremist web forums and within the organisation, debate is raging about how the US will respond to the beheading of two of its citizens, and what Britain and Europe may do if its nationals are harmed.

A growing school of though is that the gruesome, highly public, deaths of James Foley and Stephen Sotloff, have done what three blood-soaked years in Syria and Iraq had previously failed to do: galvanised war-weary western leaders and their deeply sceptical publics to a common and fast growing enemy that may eventually point its turrets their way.

Advocates of toning down the brazen violence say that while such tactics have a strong terror shock value among communities they want to conquer, they also stir sleeping giants. And if Isis is to continue its quest for dominance, having superpowers collectively enraged so soon might not help further such goals.

The group has enormous momentum at the moment; militarily it is manoeuvring on three fronts at once – something far beyond the Iraqi, or Syrian armies. Along the way, it is collecting large numbers of Sunnis on both sides of the now redundant border. Some are joining out of coercion, others from fear and a smaller number from a conviction that the jihadis share their values and are acting out pre-ordained prophecies.

Whatever their motivation, Iraq's Sunni minority shares a common sense of being estranged from any semblance of a political process ever since Saddam Hussein was ousted in Iraq and Shia Islamic Iran established itself as a post-occupation power. Syria's Sunni majority, especially in the north and east, has been partly subservient to a Shia-aligned Alawite regime for more than three decades longer. Together they make a formidable support base.

Supporters in favour of a less confrontational approach say that Isis needs this stunning progress to continue if it is to make good its goal of re-establishing a caliphate across ancient Islamic lands.

After declaring the establishment of a new caliphate, what to do now is at the behest of the self-styled caliph, Abu Bakr al-Baghdadi, and a tightly-knit military council that makes all the group's strategic decisions.

Some who study Isis closely say Baghdadi is aiming for an apocalyptic showdown that he wants to bring on sooner rather than later. Interpretations of Koranic teachings underpin all of what Baghdadi does.

And high on the list of teachings being adhered to by Isis is a 1,400 year old prediction that Muslims and Christians would fight a pre-apocalyptic battle in a place called Dabek. Since establishing themselves as a force in northern Syria in May 2013, Isis members have focused on small hamlet of 4,000 people some 30 miles south of the Turkish border, called Murj Dabek. This, to many among Isis, is ground zero of the war, a place where ancient prophecies will be thrashed out in an existential battle between the faiths.

"Baghdadi wants to bring the Americans into a war with him so he will prove what was written in the Quran and the prophecies that (Christians) will fight against the Muslims," said a leading Iraqi expert on Isis, Hisham al-Hashimi. "He wants to prove that he is the leader of Muslims. Having the Americans bomb him is not at odds with spreading the caliphate. His dream is a real jihad against the Crusaders."

Baghdadi does not fear the Arab world's armies. He has tapped into the ruins of a body politic across much of the Arab world that has spectacularly failed to share power or respond to the will of the street. He knows from his time in Iraq, both in US prisons and on the battlefields that to be realistically confronted, the US, or another power will need to ally with local backers.

He also knows, that without an occupying army – and re-occupying central Arabia is something that Barack Obama still seems repulsed by – it will be difficult to splinter the Sunni support base that now stands with him.

"There are military leaders working with him, former Saddam henchmen," said one former middle-ranking member of Isis who left the group before it changed the face of the Middle East in June with its advances into Mosul and Tikrit. "They were not with us then. They thought we were a bus that they wanted to get to their destination. But now, from what I know of them, they are just as ruthless, just as committed. These people are running the war in places like Tikrit. Even if they part ways, they will help Islamic State win."