In June 2014 the armed forces of the group that at the time called itself the Islamic State of Iraq and al-Sham (Isis or Isil) seized Mosul, the second or third most populous city of Iraq. The United States had invested, or perhaps wasted, according to one estimate US$25bn on the Iraqi army, which now fled in fear.

Already Isis had dissolved the border that divided Iraq and Syria since the end of world war one, which it derisively described as the fruit of the Anglo–French “Sykes–Picot” conspiracy. Shortly after, Isis shortened its name to the Islamic State and declared that the centuries-old caliphate abolished in 1924 by the Turkish president Kemal Atatürk was now reborn.

The caliph was the former head of Isis, Abu Bakr al-Baghdadi. According to the Islamic State, it was to Baghdadi that the more than one and a half billion Muslims living in every continent across the globe now owed allegiance.

Isis had been seizing territory in Iraq and Syria during the past two years or more. After Mosul fell, the Islamic State was the size of Belgium. And yet it is also true that until that moment, apart from a handful of scholars and a small number of military strategists and intelligence officers, the advance of Isis had scarcely been given a second thought in the United States.

In early January 2014, the editor of the New Yorker, David Remnick, conducted a wide-ranging foreign policy interview with President Barack Obama. A few days earlier, as Remnick pointed out to Obama, the Sunni city of Fallujah had fallen to Isis. He challenged Obama: “Even in the period that you’ve been on vacation in the last couple of weeks, in Iraq, in Syria, of course, in Africa, al-Qaeda is resurgent.”

Obama replied in a dismissive tone: “Yes, but David, I think the analogy we use around here sometimes, and I think [it] is accurate, is if a JV [junior varsity] team puts on Lakers uniforms, that doesn’t make them Kobe Bryant.”

This comment became notorious. At this time the Obama administration was obviously not concerned with the growing power of Isis. Neither Remnick nor Obama even seemed to be aware that relations between al-Qaeda and Isis had broken down. As it happens, in June 2014 I attended a conference in Canberra which was also attended by Kurt Campbell, a former very senior member of the US state department, recently retired. He seemed no better informed nor less perplexed by the turn of events in Iraq than I was.

After the fall of Mosul, western indifference to the rise of Isis, now the Islamic State, quickly evaporated. As speculation about the security of even Baghdad mounted, the world learned of the many dark and barbarous deeds – the public beheadings of western hostages; the massacres of captured enemy troops, of Shia and Alawite “heretical” Muslims and of the Druze and Yazidis, all with an openly admitted genocidal purpose; the creation of markets in women for the purpose of sexual slavery; the stoning to death of adulterous wives; the restoration of punishment by crucifixion; the burnings, in one famous case of a captured and caged Jordanian pilot; the killing of homosexuals, thrown from the roof of a town’s tallest building. All of these deaths were public. Many became known to the world through widely disseminated high-quality videos and online magazines.

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During the period of my research, the Islamic State published in several languages, including English, a quarterly online magazine called Dabiq. Dabiq was clearly written by a number of intellectuals with a grasp of the principal sources of the religion of Islam. Each issue was between 60 and 80 pages, and included a number of well-written articles, sometimes very lengthy.

In Dabiq, no theme was more important than the Islamic State’s desire to destroy those it regarded as its historical and current enemies – especially the Shia Muslims, the Rafida; their Syrian cousins, the Alawites or Nusayris; the fallen apostate peoples, the Yazidis and the Druze; the Christian west, the “Crusaders”; and the eternal enemy of the Muslims, the Jews. Despite its intellectual sophistication, each issue of Dabiq contained eschatological articles, concerning, for example, the nature of the Dajjal (the Rafida equivalent of the Antichrist) or the coming battles at the End of Days, from whose prophesied battleground, the town of Dabiq, the magazine took its name.

The magazine had several regular features. Each issue provided details of the military triumphs of the Islamic State and its affiliates, including both the planned operations and the lone-wolf attacks on its Crusader enemies in the west. (It was, however, conspicuously silent about the setbacks.) Each issue contained gruesome photos of the enemies it had dispatched – the beheaded western or Japanese hostages, the immolated Jordanian pilot, and dozens showing the corpses of the captured enemy troops and of the Shias, Alawites or Yazidis it had slaughtered.

Each issue told the story of the noble mujahideen “martyrs”, under the rubric “Among the Believers Are Men”. In a regular column called “From Our Sisters”, questions concerning women were discussed – the benefits of polygyny; the merits of sexual slavery; and the mothers’ indispensable role in providing a suitable education for the “lion cubs” – the next generation of soldiers. One of Dabiq’s preoccupations was the horror of life in the infidel (kuffar) societies of the west and the religious obligation of Muslims around the world to undertake migration to the Islamic State (hijrah) now that the caliphate had been established.

Dabiq was obsessed by the internal micro-politics of the civil war in Syria and especially the Islamic State’s enmity with its former Syrian ally there, the al-Nusra Front. It also became obsessed with the weakness and betrayal of the Muslim cause of Ayman al-Zawahiri, the current leader of al-Qaeda. In several issues, Dabiq published strange non-Islamic articles by one of its western hostages, John Cantlie, who, in the sarcastic tone of a contemporary “Lord Haw-Haw”, castigated the United States for its cruelty and its folly. Dabiq contained a regular feature it called “In the Words of the Enemy”. Here, special pleasure was taken in the comments of leading US generals, politicians or journalists expressing anxiety about the growing strength of the Islamic State and the danger it posed.

The pages of Dabiq express a remarkably consistent and internally coherent ideology, no less consistent and coherent than the Marxism–Leninism of the Soviet Union during the era of Stalin; more consistent and coherent, in my view, than the ideology of Nazism. As one can assume that Dabiq represents the official world-view of the Islamic State, it is surprising how little it has been analysed by specialist scholars. It has been my primary source for an understanding of the mind of the current leadership of the Islamic State.

Political ideologies take decades to form. The mind of the Islamic State represents the latest iteration of an ideology that has been developing over the past 50 years. Among scholars there is little disagreement about who have been its most significant contributors. There exists a more or less general consensus that the ideology of the Islamic State is founded upon the prison writings of the revolutionary Egyptian Muslim Brother Sayyid Qutb, in particular some sections of his commentary In the Shade of the Qur’an, but most importantly his late visionary work Milestones, published in 1964.

Qutb argued that the entire world, including the supposedly Muslim states, had fallen into a time of pre-Islamic ignorance, jahiliyya, or pagan darkness. He called upon the small number of true Muslims to form a revolutionary vanguard to restore the light of Islam to the world. Because of his reference to the vanguard, the eminent scholar of radical Islam Gilles Kepel has described Milestones as the Islamist version of Lenin’s What is to Be Done?

This seems to me mistaken. Although Milestones played a part in the decision of the Egyptian court to send Qutb to the gallows, unlike Lenin’s seminal manifesto, the practical political implications of Qutb’s masterwork were ambiguous. Nonetheless, so powerful was Qutb’s vision that several scholars have termed the ideology that provided the foundation of the Islamic State “Qutbism”.

The first answer to the question about what was to be done by those who hoped to implement Qutb’s vision came a decade and a half after the master’s death, with The Neglected Duty, the underground revolutionary working paper of an Egyptian electrical engineer, Muhammad Abd al-Salam Faraj. Faraj called upon Muslims to fulfil their religious obligation of jihad – which he, like Qutb, interpreted as violent struggle in the service of God – and to lay the foundation of a truly Islamic state. His favoured method was assassination of the most important contemporary enemy of the Muslims, the apostate “Pharaoh”, a clear reference to the president of Egypt, Anwar Sadat.

Faraj regarded the “near enemy”, the Egyptian state, as a more strategically significant target than the “far enemy”, the Crusader Americans and the Zionist Jews. In 1981 Faraj’s group succeeded in their plot to kill Sadat. As a consequence, Faraj’s life, like Qutb’s, ended on the gallows. His pamphlet nonetheless represented the beginning of a 20-year era during which Egyptian jihadi revolutionaries, under the spell of Qutb’s prison writings, conducted a prolonged, bloody and ultimately unsuccessful revolutionary struggle against the “near enemy” – with plots to assassinate the apostate leaders, the taghut; to stage military coups; to incite popular uprisings.

A more influential answer to the question of what was to be done to implement the Qutbist vision was provided shortly after Faraj’s death by the Palestinian Islamic scholar Abdullah Azzam. After the 1979 Soviet invasion of Afghanistan, Azzam moved to Peshawar and established an office for the organisation of Arabs who had journeyed to Afghanistan to support the local jihadi fighters, the mujahideen.

In remarkably eloquent speeches, in the articles of his magazine, al-Jihad, and especially in two of his short books, Defence of the Muslim Lands and Join the Caravan, Azzam called upon Muslims across the globe to defend their nation, the umma, which was now under direct threat. Azzam insisted that defence of the umma through jihad, in the face of the infidel invader, was not a collective but an individual duty for each Muslim, as obligatory as one of the five pillars of the faith, such as praying and fasting.

Azzam was assassinated in 1989, nobody knows for certain by whom. But by the time of his death, he had convinced a generation of revolutionary Muslims that the Afghan and Arab mujahideen had been responsible, through God’s grace and through their glorious martyrs’ deaths, for crippling the military might of the Soviet Union in Afghanistan.

Moreover, he saw in the triumphant struggles of the mujahideen in Afghanistan a portent of a worldwide Islamic revival – in the jahili Muslim lands of the present; in his homeland, Palestine, and all other Muslim lands that had been conquered by the Crusaders; eventually across the entire globe.

In Afghanistan, Azzam had worked for a time with a wealthy Saudi of Yemeni background, Osama bin Laden. Eventually their ways parted. Having absorbed both Qutb’s vision and Azzam’s triumphalism and ambition (which he assimilated into his Saudi sensibility), in 1988 Bin Laden created in Afghanistan an organisation he called al-Qaeda, which was eventually to become the first global army of jihadis.

In 1996, upon his return to Afghanistan, Bin Laden set his sights on the destruction of the only remaining superpower, the United States. In his view, the US was under the control of the Jews. It had been responsible for inflicting upon the Muslims the cruellest wound, the creation of a Jewish state at the very heart of the umma. It was also the indispensable patron and protector of the taghut regimes throughout the supposedly Muslim world. Perhaps worst of all, since 1990, by invitation from the Saudi royal family after Iraq’s invasion of Kuwait, the US had occupied the land of the two holiest cities of Islam, Mecca and Medina. In 1998 al-Qaeda called upon the mujahideen to kill Americans and Jews.

One of the signatories of Bin Laden’s fatwa was the most influential Egyptian Qutbist revolutionary of the past 20 years, Ayman al-Zawahiri. In mid-2001 Zawahiri led a part of his group, al-Jihad, into al-Qaeda. Their union was consummated with a double conversion. Zawahiri adopted Bin Laden’s concentration on the far enemy. For his part, Bin Laden adopted the tactic that Zawahiri and other Egyptian Islamist revolutionaries had long embraced: suicide bombings, or what the Qutbists now called “martyrdom operations” – a vital tactic in technologically unequal, asymmetrical warfare. The first fruit of their union was 9/11, the attack on the twin towers in New York and the Pentagon. By this time, Zawahiri was responsible, most comprehensively in his 2001 memoir, Knights under the Prophet’s Banner, for systematising the political ideology founded on the vision of Sayyid Qutb.

The ideology had not yet reached its latest and perhaps final destination. One consequence of 9/11 was the March 2003 US–led invasion and occupation of Iraq. As it happened, one leader of the Sunni resistance was a Jordanian revolutionary jihadi, Abu Musab al-Zarqawi, who had established his own training camp in Afghanistan in 1999 at Herat and then, after the US invasion of Afghanistan and attack on the Taliban, had moved to Iraq via Iran in preparation for the generally anticipated US invasion.

Zarqawi was responsible for adding several new elements to the political ideology inspired by Qutb and systematised by Zawahiri. Zarqawi injected into its heart a sectarian and exterminatory hatred of the Shia.

Drawing upon the strategic theory of Abu Bakr Naji, the author of The Management of Savagery, and the theology of a jihadi scholar, Abu Abdullah al-Muhajir, the author of a work most commonly known as The Jurisprudence of Blood, Zarqawi extended vastly the purpose, the method and the permissible scope of killing.

He conducted public beheadings of hostages. He greatly expanded the role of suicide bombings, with increasingly callous theological justifications, targeting not only the occupation forces and their Iraqi allies but also innocent Shia civilians and politically unfriendly Sunnis, earning for himself the well-deserved title of “the sheikh of the slaughterers”.

Before Zarqawi, the creation of an Islamic State, and even more the re-establishment of the caliphate, had been distant dreams of the Qutbists. With Zarqawi they became pressing items of a current political agenda. Before Zarqawi, too, the thought of the Qutbists had been largely unaffected by the eschatological or apocalyptic undercurrents of Sunni Islam. Under Zarqawi these began to rise to the surface.

Zarqawi was killed in 2006. Nonetheless, his two successors, Abu Omar al-Baghdadi, who was killed in 2010, and Abu Bakr al-Baghdadi, the first caliph of the Islamic State, embraced fully and even extended the anti-Shia sectarianism, the strategic and jurisprudential savagery, the immediate Islamic state-building ambition, and the apocalyptic dimension that Zarqawi had injected into the political ideology that had grown from the vision of Qutb.

A supporter of the Islamic State, thought to be the Yemeni journalist Abdulelah Haider Shaye, captured with admirable precision in a single sentence its ideological genealogy: “The Islamic State was drafted by Sayyid Qutb, taught by Abdullah Azzam, globalised by Osama bin Laden, transferred to reality by Abu Musab al-Zarqawi, and implemented by al-Baghdadis: Abu Omar and Abu Bakr.”

Robert Manne is emeritus professor of politics and vice-chancellor’s fellow at La Trobe University in Melbourne. This is an edited extract of his The Mind of the Islamic State published this month by Black Inc