Islamic State, often known as ISIS, is one of the greatest unintended consequences in history. Its predecessor emerged from the chaos that followed the American invasion of Iraq, and the overthrow of the Ba'athist regime, in 2003. After it, jihadis began flocking to the country, through its newly-porous borders, to attack the Americans, whom they regarded as latter-day crusaders. The Syrian regime - fearing that it would be the next American target - facilitated the transit of fighters it hoped would keep the invaders busy in Iraq.
Groups of fighters coalesced into Al-Qaeda in Iraq, the local affiliate of Osama bin Laden's international network. The authors emphasise the influence on AQI of Abu Musab al Zarqawi, an alcoholic hoodlum who had embraced a fundamentalist, sectarian mutation of Islam.
His followers' attacks on Shias, and Shia mosques, and the ultraviolence they employed, appalled even the hardened terrorists in Al-Qaeda Central, and caused a split between the two organisations. AQI is now Islamic State, an organisation in confident control of vast stretches of territory in Iraq and Syria, and rich from robbing banks and trafficking oil.
The jihadis are master propagandists, and the authors' description of the workings of the ISIS publicity machine is one of the strongest parts of a book full of insights. Al-Qaeda, they argue, offers Muslims a narrative of weakness: it reminds them of their defeats and humiliations at the hands of the West, and exhorts them to continue to rise and resist until final victory in the distant future.
But ISIS talks a different language, one that tells of a Muslim army on the march, seizing and holding territory, slaying infidels and apostates. It has announced the establishment of an Islamic state or Caliphate. ISIS videos intersperse depictions of martial success, and slaughtered enemies with glimpses of a functioning new Islamic society, with its own police force and courts and comfortable nursing homes for its elderly.
Meanwhile, al-Qaeda distributes clunky videos of its elderly bearded leader, Ayman al Zawahiri, staring into a camera, delivering a long-winded sermon. To impressionable Muslims, ISIS represents victory, now.
Jihadis have taken to the internet and social media with enthusiasm, migrating from online forums to Twitter, on which they have been able to communicate freely until very recently. American intelligence agencies have an ambivalent attitude towards the jihadi presence on Twitter, mining some accounts for information, while putting pressure on the company to close others they deem dangerous.
Twitter has become an important recruitment tool for ISIS: would-be jihadis make their way to Turkish towns near the Syrian border, tweet their whereabouts to a contact, and await transport to the Islamic State. ISIS even 'focus-grouped' the announcement of a caliphate on Twitter.
Sedulous research has enabled the authors to build a picture of life under ISIS. It has established, and sustains itself, by violence: killing blunts jihadis' sense of empathy, and dulls the natural human instinct to question the morality or judiciousness of an action. ISIS stones adulterers to death, throws homosexuals from rooftops. In towns it has seized children playing on streets on which corpses hang from trees and lamp-posts.
Many of the subjects that used to figure on the educational curriculum - art, music, history, sport - are banned. The indoctrination of children - also a feature of life under the Khmer Rouge - is the means by which ISIS hopes to ensure the loyalty of the coming generation. It exposes them from an early age to its narrow sectarian version of Islam. Instead of toys, children are given blond-haired dolls on which to practice beheading; when they are older they will get a chance to work on people.
Islamic State is practising 'child abuse on an industrial scale'. Questions that the authors pose linger in the mind: when ISIS is finally defeated, and its fighters interned, what is the international community to do with children who have killed and mutilated on behalf of ISIS? Does it simply forgive them their crimes, given the indoctrination they were subject to?
We have time to ponder these questions, for ISIS is far from defeated. Iraqi and Kurdish forces, supported by American aircraft, are slowly pushing back the borders of the caliphate, bearing down on Mosul, the city in which the caliphate was declared on June 29 2014; but elsewhere ISIS is expanding. Its Yemeni affiliate killed and injured hundreds in attacks on Shia mosques in Sana'a in March; it has a presence now in Libya, in the Sinai peninsula, and allies in West Africa.
An ISIS commander in Iraq told Reuters recently that the airstrikes and shelling his fighters were enduring were a 'nightmare'. His remark begs a question: how high is morale among the fighters?
Jihadis believe that their victories are divinely-inspired. But do doubts cross their minds as they heave the bodies of dead comrades on to pick-up trucks and hurry off before the advancing enemy? Perhaps not: ISIS is, after all, a cult and members of cults are prone to cognitive dissonance - an ability to accept reality as it is, while cleaving to ingrained or indoctrinated beliefs which contradict that reality.
Stern and Berger argue for offensives against ISIS on two fronts - in the field and online. By containing it militarily, the international community could 'let it rot'. Drones and spotter planes could gather photographic evidence of the squalor in Islamic State-held areas - the uncollected rubbish for example - for online distribution.
Opponents of ISIS could make better use of accounts of atrocities it has perpetrated against Sunni Muslims who refused to cooperate with it. On Twitter the war has already begun to go badly for ISIS. The jihadis no longer have a free run on the service: under American government pressure, Twitter has begun acting against pro-ISIS accounts, of which the authors estimate there are some 45,000. An ISIS supporter can easily open another account, but it takes time to regain attention and re-acquire followers; and many tend to give up when their accounts are closed for a third, fourth, or fifth time. A sense of frustration may explain recent ISIS threats against Twitter executives.
As the authors of an illuminating book remind us, there are still those who believe in white supremacy, long after Nazism and Apartheid have been consigned to history. ISIS will probably succumb to the military pressure but its mistaken, pernicious ideology will likely outlive it.
Isis: The State of Terror, Jessica Stern and JM Berger, Allen Hall, pbk, 256p, £14.99
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