Graeme Wood at The Atlantic has written a
10,000 word article that describes in detail the underlying ideological and religious thinking behind IS. He says, correctly, that unless the West understands it, there is no way to defeat it.
But as you read it, you see that outside of military annihilation, there is no way to defeat it anyway (although Wood thinks that containment can work over time, causing new recruits to become disillusioned at the failure of the caliphate to continuously expand.)
One major point is that their leaders are not crazy. Their beliefs are consistent and if you are willing to listen to them, they will tell you their strategy and tactics.
The ideological purity of the Islamic State has one compensating virtue: it allows us to predict some of the group’s actions. Osama bin Laden was seldom predictable. He ended his first television interview cryptically. CNN’s Peter Arnett asked him, “What are your future plans?” Bin Laden replied, “You’ll see them and hear about them in the media, God willing.” By contrast, the Islamic State boasts openly about its plans—not all of them, but enough so that by listening carefully, we can deduce how it intends to govern and expand.
In London, Choudary and his students provided detailed descriptions of how the Islamic State must conduct its foreign policy, now that it is a caliphate. It has already taken up what Islamic law refers to as “offensive jihad,” the forcible expansion into countries that are ruled by non-Muslims. “Hitherto, we were just defending ourselves,” Choudary said; without a caliphate, offensive jihad is an inapplicable concept. But the waging of war to expand the caliphate is an essential duty of the caliph.
Choudary took pains to present the laws of war under which the Islamic State operates as policies of mercy rather than of brutality. He told me the state has an obligation to terrorize its enemies—a holy order to scare the shit out of them with beheadings and crucifixions and enslavement of women and children, because doing so hastens victory and avoids prolonged conflict.
Choudary’s colleague Abu Baraa explained that Islamic law permits only temporary peace treaties, lasting no longer than a decade. Similarly, accepting any border is anathema, as stated by the Prophet and echoed in the Islamic State’s propaganda videos. If the caliph consents to a longer-term peace or permanent border, he will be in error. Temporary peace treaties are renewable, but may not be applied to all enemies at once: the caliph must wage jihad at least once a year. He may not rest, or he will fall into a state of sin.
Another, which I believe that Wood downplays, is that
IS cannot be stopped by religious arguments - because their entire point is to bring Islam back to the 7th century, back to Mohammed's own practices. And any Muslim who argues that Mohammed's methods don't apply nowadays cannot win an argument against IS:
It would be facile, even exculpatory, to call the problem of the Islamic State “a problem with Islam.” The religion allows many interpretations, and Islamic State supporters are morally on the hook for the one they choose. And yet simply denouncing the Islamic State as un-Islamic can be counterproductive, especially if those who hear the message have read the holy texts and seen the endorsement of many of the caliphate’s practices written plainly within them.
Muslims can say that slavery is not legitimate now, and that crucifixion is wrong at this historical juncture. Many say precisely this. But they cannot condemn slavery or crucifixion outright without contradicting the Koran and the example of the Prophet. “The only principled ground that the Islamic State’s opponents could take is to say that certain core texts and traditional teachings of Islam are no longer valid,” Bernard Haykel says. That really would be an act of apostasy.
The Islamic State’s ideology exerts powerful sway over a certain subset of the population. Life’s hypocrisies and inconsistencies vanish in its face. Musa Cerantonio and the Salafis I met in London are unstumpable: no question I posed left them stuttering. They lectured me garrulously and, if one accepts their premises, convincingly. To call them un-Islamic appears, to me, to invite them into an argument that they would win. If they had been froth-spewing maniacs, I might be able to predict that their movement would burn out as the psychopaths detonated themselves or became drone-splats, one by one. But these men spoke with an academic precision that put me in mind of a good graduate seminar. I even enjoyed their company, and that frightened me as much as anything else.
The author underplays the appeal of a non-hypocritical Islam, when Islam itself has no theological alternative to believing that Mohammed was the perfect prophet and example to mankind. Young people who embrace Islam will be far more likely to choose the strain that is the most internally consistent, and as it stands, that is IS.
Wood brings a single counterexample of Salafis, who also believe in Islamic purity with the same fervor, but also believe that the time to bring in that era is not yet here:
There is, however, another strand of Islam that offers a hard-line alternative to the Islamic State—just as uncompromising, but with opposite conclusions. This strand has proved appealing to many Muslims cursed or blessed with a psychological longing to see every jot and tittle of the holy texts implemented as they were in the earliest days of Islam. Islamic State supporters know how to react to Muslims who ignore parts of the Koran: with takfir and ridicule. But they also know that some other Muslims read the Koran as assiduously as they do, and pose a real ideological threat.
Baghdadi is Salafi. The term Salafi has been villainized, in part because authentic villains have ridden into battle waving the Salafi banner. But most Salafis are not jihadists, and most adhere to sects that reject the Islamic State. They are, as Haykel notes, committed to expanding Dar al-Islam, the land of Islam, even, perhaps, with the implementation of monstrous practices such as slavery and amputation—but at some future point. Their first priority is personal purification and religious observance, and they believe anything that thwarts those goals—such as causing war or unrest that would disrupt lives and prayer and scholarship—is forbidden.
But these types of Salafists are unlikely to be dragged into an theological battle with IS, because it would ultimately become a political battle and these "quiet" Salafis are not equipped to fight on that battlefield.
This is an important article, well worth reading.