The Islamic State is no mere collection of psychopaths. It is a religious group with carefully considered beliefs, among them that it is a key agent of the coming apocalypse. Here’s what that means for its strategy—and for how to stop it. 
 
 What is the Islamic State? Where did it come from, and what are its intentions? The simplicity of these questions can be deceiving, and few Western leaders seem to know the answers. In December, The New York Times published confidential comments by Major General Michael K. Nagata, the Special Operations commander for the United States in the Middle East, admitting that he had hardly begun figuring out the Islamic State’s appeal. “We have not defeated the idea,” he said. “We do not even understand the idea.” In the past year, President Obama has referred to the Islamic State, variously, as “not Islamic” and as al-Qaeda’s “jayvee team,” statements that reflected confusion about the group, and may have contributed to significant strategic errors. Related Story What to Do About ISIS? The group seized Mosul, Iraq, last June, and already rules an area larger than the United Kingdom. Abu Bakr al-Baghdadi has been its leader since May 2010, but until last summer, his most recent known appearance on film was a grainy mug shot from a stay in U.S. captivity at Camp Bucca during the occupation of Iraq. Then, on July 5 of last year, he stepped into the pulpit of the Great Mosque of al-Nuri in Mosul, to deliver a Ramadan sermon as the first caliph in generations—upgrading his resolution from grainy to high-definition, and his position from hunted guerrilla to commander of all Muslims. The inflow of jihadists that followed, from around the world, was unprecedented in its pace and volume, and is continuing. Our ignorance of the Islamic State is in some ways understandable: It is a hermit kingdom; few have gone there and returned. Baghdadi has spoken on camera only once. But his address, and the Islamic State’s countless other propaganda videos and encyclicals, are online, and the caliphate’s supporters have toiled mightily to make their project knowable. We can gather that their state rejects peace as a matter of principle; that it hungers for genocide; that its religious views make it constitutionally incapable of certain types of change, even if that change might ensure its survival; and that it considers itself a harbinger of—and headline player in—the imminent end of the world. 
 
 The Islamic State, also known as the Islamic State of Iraq and al-Sham (ISIS), follows a distinctive variety of Islam whose beliefs about the path to the Day of Judgment matter to its strategy, and can help the West know its enemy and predict its behavior. Its rise to power is less like the triumph of the Muslim Brotherhood in Egypt (a group whose leaders the Islamic State considers apostates) than like the realization of a dystopian alternate reality in which David Koresh or Jim Jones survived to wield absolute power over not just a few hundred people, but some 8 million. A year-by-year catalogue of some of the magazine's most momentous work. 
 
 Read more We have misunderstood the nature of the Islamic State in at least two ways. First, we tend to see jihadism as monolithic, and to apply the logic of al-Qaeda to an organization that has decisively eclipsed it. The Islamic State supporters I spoke with still refer to Osama bin Laden as “Sheikh Osama,” a title of honor. But jihadism has evolved since al-Qaeda’s heyday, from about 1998 to 2003, and many jihadists disdain the group’s priorities and current leadership. Bin Laden viewed his terrorism as a prologue to a caliphate he did not expect to see in his lifetime. His organization was flexible, operating as a geographically diffuse network of autonomous cells. The Islamic State, by contrast, requires territory to remain legitimate, and a top-down structure to rule it. (Its bureaucracy is divided into civil and military arms, and its territory into provinces.) Related Story The Roots of the Islamic State’s Appeal We are misled in a second way, by a well-intentioned but dishonest campaign to deny the Islamic State’s medieval religious nature. Peter Bergen, who produced the first interview with bin Laden in 1997, titled his first book Holy War, Inc. in part to acknowledge bin Laden as a creature of the modern secular world. Bin Laden corporatized terror and franchised it out. He requested specific political concessions, such as the withdrawal of U.S. forces from Saudi Arabia. His foot soldiers navigated the modern world confidently. On Mohamed Atta’s last full day of life, he shopped at Walmart and ate dinner at Pizza Hut. 
 
 There is a temptation to rehearse this observation—that jihadists are modern secular people, with modern political concerns, wearing medieval religious disguise—and make it fit the Islamic State. In fact, much of what the group does looks nonsensical except in light of a sincere, carefully considered commitment to returning civilization to a seventh-century legal environment, and ultimately to bringing about the apocalypse. 
 
 The most-articulate spokesmen for that position are the Islamic State’s officials and supporters themselves. They refer derisively to “moderns.” In conversation, they insist that they will not—cannot—waver from governing precepts that were embedded in Islam by the Prophet Muhammad and his earliest followers. They often speak in codes and allusions that sound odd or old-fashioned to non-Muslims, but refer to specific traditions and texts of early Islam. To take one example: In September, Sheikh Abu Muhammad al-Adnani, the Islamic State’s chief spokesman, called on Muslims in Western countries such as France and Canada to find an infidel and “smash his head with a rock,” poison him, run him over with a car, or “destroy his crops.” To Western ears, the biblical-sounding punishments—the stoning and crop destruction—juxtaposed strangely with his more modern-sounding call to vehicular homicide. (As if to show that he could terrorize by imagery alone, Adnani also referred to Secretary of State John Kerry as an “uncircumcised geezer.”) But Adnani was not merely talking trash. His speech was laced with theological and legal discussion, and his exhortation to attack crops directly echoed orders from Muhammad to leave well water and crops alone—unless the armies of Islam were in a defensive position, in which case Muslims in the lands of kuffar, or infidels, should be unmerciful, and poison away. 
 
 The reality is that the Islamic State is Islamic. Very Islamic. Yes, it has attracted psychopaths and adventure seekers, drawn largely from the disaffected populations of the Middle East and Europe. But the religion preached by its most ardent followers derives from coherent and even learned interpretations of Islam. Related Story Could ISIS Exist Without Islam? Virtually every major decision and law promulgated by the Islamic State adheres to what it calls, in its press and pronouncements, and on its billboards, license plates, stationery, and coins, “the Prophetic methodology,” which means following the prophecy and example of Muhammad, in punctilious detail. Muslims can reject the Islamic State; nearly all do. But pretending that it isn’t actually a religious, millenarian group, with theology that must be understood to be combatted, has already led the United States to underestimate it and back foolish schemes to counter it. We’ll need to get acquainted with the Islamic State’s intellectual genealogy if we are to react in a way that will not strengthen it, but instead help it self-immolate in its own excessive zeal. 
 
 I. Devotion In November, the Islamic State released an infomercial-like video tracing its origins to bin Laden. It acknowledged Abu Musa’b al Zarqawi, the brutal head of al‑Qaeda in Iraq from roughly 2003 until his killing in 2006, as a more immediate progenitor, followed sequentially by two other guerrilla leaders before Baghdadi, the caliph. Notably unmentioned: bin Laden’s successor, Ayman al Zawahiri, the owlish Egyptian eye surgeon who currently heads al‑Qaeda. Zawahiri has not pledged allegiance to Baghdadi, and he is increasingly hated by his fellow jihadists. His isolation is not helped by his lack of charisma; in videos he comes across as squinty and annoyed. But the split between al-Qaeda and the Islamic State has been long in the making, and begins to explain, at least in part, the outsize bloodlust of the latter. 
 
 Zawahiri’s companion in isolation is a Jordanian cleric named Abu Muhammad al Maqdisi, 55, who has a fair claim to being al-Qaeda’s intellectual architect and the most important jihadist unknown to the average American newspaper reader. On most matters of doctrine, Maqdisi and the Islamic State agree. Both are closely identified with the jihadist wing of a branch of Sunnism called Salafism, after the Arabic al salaf al salih, the “pious forefathers.” These forefathers are the Prophet himself and his earliest adherents, whom Salafis honor and emulate as the models for all behavior, including warfare, couture, family life, even dentistry. The Islamic State awaits the army of “Rome,” whose defeat at Dabiq, Syria, will initiate the countdown to the apocalypse. Maqdisi taught Zarqawi, who went to war in Iraq with the older man’s advice in mind. In time, though, Zarqawi surpassed his mentor in fanaticism, and eventually earned his rebuke. At issue was Zarqawi’s penchant for bloody spectacle—and, as a matter of doctrine, his hatred of other Muslims, to the point of excommunicating and killing them. In Islam, the practice of takfir, or excommunication, is theologically perilous. “If a man says to his brother, ‘You are an infidel,’ ” the Prophet said, “then one of them is right.” If the accuser is wrong, he himself has committed apostasy by making a false accusation. The punishment for apostasy is death. And yet Zarqawi heedlessly expanded the range of behavior that could make Muslims infidels. 
 
 Maqdisi wrote to his former pupil that he needed to exercise caution and “not issue sweeping proclamations of takfir” or “proclaim people to be apostates because of their sins.” The distinction between apostate and sinner may appear subtle, but it is a key point of contention between al-Qaeda and the Islamic State. Related Story What Motivates Terrorists? Denying the holiness of the Koran or the prophecies of Muhammad is straightforward apostasy. But Zarqawi and the state he spawned take the position that many other acts can remove a Muslim from Islam. These include, in certain cases, selling alcohol or drugs, wearing Western clothes or shaving one’s beard, voting in an election—even for a Muslim candidate—and being lax about calling other people apostates. Being a Shiite, as most Iraqi Arabs are, meets the standard as well, because the Islamic State regards Shiism as innovation, and to innovate on the Koran is to deny its initial perfection. (The Islamic State claims that common Shiite practices, such as worship at the graves of imams and public self-flagellation, have no basis in the Koran or in the example of the Prophet.) That means roughly 200 million Shia are marked for death. So too are the heads of state of every Muslim country, who have elevated man-made law above Sharia by running for office or enforcing laws not made by God. 
 
 Following takfiri doctrine, the Islamic State is committed to purifying the world by killing vast numbers of people. The lack of objective reporting from its territory makes the true extent of the slaughter unknowable, but social-media posts from the region suggest that individual executions happen more or less continually, and mass executions every few weeks. Muslim “apostates” are the most common victims. Exempted from automatic execution, it appears, are Christians who do not resist their new government. Baghdadi permits them to live, as long as they pay a special tax, known as the jizya, and acknowledge their subjugation. The Koranic authority for this practice is not in dispute. 
 
 Centuries have passed since the wars of religion ceased in Europe, and since men stopped dying in large numbers because of arcane theological disputes. Hence, perhaps, the incredulity and denial with which Westerners have greeted news of the theology and practices of the Islamic State. Many refuse to believe that this group is as devout as it claims to be, or as backward-looking or apocalyptic as its actions and statements suggest. 
 
 Their skepticism is comprehensible. In the past, Westerners who accused Muslims of blindly following ancient scriptures came to deserved grief from academics—notably the late Edward Said—who pointed out that calling Muslims “ancient” was usually just another way to denigrate them. Look instead, these scholars urged, to the conditions in which these ideologies arose—the bad governance, the shifting social mores, the humiliation of living in lands valued only for their oil. Without acknowledgment of these factors, no explanation of the rise of the Islamic State could be complete. But focusing on them to the exclusion of ideology reflects another kind of Western bias: that if religious ideology doesn’t matter much in Washington or Berlin, surely it must be equally irrelevant in Raqqa or Mosul. When a masked executioner says Allahu akbar while beheading an apostate, sometimes he’s doing so for religious reasons. Related Story The Phony Islam of ISIS Many mainstream Muslim organizations have gone so far as to say the Islamic State is, in fact, un-Islamic. It is, of course, reassuring to know that the vast majority of Muslims have zero interest in replacing Hollywood movies with public executions as evening entertainment. But Muslims who call the Islamic State un-Islamic are typically, as the Princeton scholar Bernard Haykel, the leading expert on the group’s theology, told me, “embarrassed and politically correct, with a cotton-candy view of their own religion” that neglects “what their religion has historically and legally required.” Many denials of the Islamic State’s religious nature, he said, are rooted in an “interfaith-Christian-nonsense tradition.” 
 
 Every academic I asked about the Islamic State’s ideology sent me to Haykel. Of partial Lebanese descent, Haykel grew up in Lebanon and the United States, and when he talks through his Mephistophelian goatee, there is a hint of an unplaceable foreign accent. According to Haykel, the ranks of the Islamic State are deeply infused with religious vigor. Koranic quotations are ubiquitous. “Even the foot soldiers spout this stuff constantly,” Haykel said. “They mug for their cameras and repeat their basic doctrines in formulaic fashion, and they do it all the time.” He regards the claim that the Islamic State has distorted the texts of Islam as preposterous, sustainable only through willful ignorance. “People want to absolve Islam,” he said. “It’s this ‘Islam is a religion of peace’ mantra. As if there is such a thing as ‘Islam’! It’s what Muslims do, and how they interpret their texts.” Those texts are shared by all Sunni Muslims, not just the Islamic State. “And these guys have just as much legitimacy as anyone else.” All Muslims acknowledge that Muhammad’s earliest conquests were not tidy affairs, and that the laws of war passed down in the Koran and in the narrations of the Prophet’s rule were calibrated to fit a turbulent and violent time. In Haykel’s estimation, the fighters of the Islamic State are authentic throwbacks to early Islam and are faithfully reproducing its norms of war. This behavior includes a number of practices that modern Muslims tend to prefer not to acknowledge as integral to their sacred texts. “Slavery, crucifixion, and beheadings are not something that freakish [jihadists] are cherry-picking from the medieval tradition,” Haykel said. Islamic State fighters “are smack in the middle of the medieval tradition and are bringing it wholesale into the present day.” Our failure to appreciate the essential differences between ISIS and al-Qaeda has led to dangerous decisions. The Koran specifies crucifixion as one of the only punishments permitted for enemies of Islam. The tax on Christians finds clear endorsement in the Surah Al-Tawba, the Koran’s ninth chapter, which instructs Muslims to fight Christians and Jews “until they pay the jizya with willing submission, and feel themselves subdued.” The Prophet, whom all Muslims consider exemplary, imposed these rules and owned slaves. 
 
 Leaders of the Islamic State have taken emulation of Muhammad as strict duty, and have revived traditions that have been dormant for hundreds of years. “What’s striking about them is not just the literalism, but also the seriousness with which they read these texts,” Haykel said. “There is an assiduous, obsessive seriousness that Muslims don’t normally have.” Before the rise of the Islamic State, no group in the past few centuries had attempted more-radical fidelity to the Prophetic model than the Wahhabis of 18th‑century Arabia. They conquered most of what is now Saudi Arabia, and their strict practices survive in a diluted version of Sharia there. Haykel sees an important distinction between the groups, though: “The Wahhabis were not wanton in their violence.” They were surrounded by Muslims, and they conquered lands that were already Islamic; this stayed their hand. “ISIS, by contrast, is really reliving the early period.” Early Muslims were surrounded by non-Muslims, and the Islamic State, because of its takfiri tendencies, considers itself to be in the same situation. Related Story The Zoolander Theory of Terrorism If al-Qaeda wanted to revive slavery, it never said so. And why would it? Silence on slavery probably reflected strategic thinking, with public sympathies in mind: when the Islamic State began enslaving people, even some of its supporters balked. Nonetheless, the caliphate has continued to embrace slavery and crucifixion without apology. “We will conquer your Rome, break your crosses, and enslave your women,” Adnani, the spokesman, promised in one of his periodic valentines to the West. “If we do not reach that time, then our children and grandchildren will reach it, and they will sell your sons as slaves at the slave market.” 
 
 In October, Dabiq, the magazine of the Islamic State, published “The Revival of Slavery Before the Hour,” an article that took up the question of whether Yazidis (the members of an ancient Kurdish sect that borrows elements of Islam, and had come under attack from Islamic State forces in northern Iraq) are lapsed Muslims, and therefore marked for death, or merely pagans and therefore fair game for enslavement. A study group of Islamic State scholars had convened, on government orders, to resolve this issue. If they are pagans, the article’s anonymous author wrote, Yazidi women and children [are to be] divided according to the Shariah amongst the fighters of the Islamic State who participated in the Sinjar operations [in northern Iraq] … Enslaving the families of the kuffar [infidels] and taking their women as concubines is a firmly established aspect of the Shariah that if one were to deny or mock, he would be denying or mocking the verses of the Koran and the narrations of the Prophet … and thereby apostatizing from Islam. II. Territory Tens of thousands of foreign Muslims are thought to have immigrated to the Islamic State. Recruits hail from France, the United Kingdom, Belgium, Germany, Holland, Australia, Indonesia, the United States, and many other places. Many have come to fight, and many intend to die. Peter R. Neumann, a professor at King’s College London, told me that online voices have been essential to spreading propaganda and ensuring that newcomers know what to believe. Online recruitment has also widened the demographics of the jihadist community, by allowing conservative Muslim women—physically isolated in their homes—to reach out to recruiters, radicalize, and arrange passage to Syria. Through its appeals to both genders, the Islamic State hopes to build a complete society. 
 
 In November, I traveled to Australia to meet Musa Cerantonio, a 30-year-old man whom Neumann and other researchers had identified as one of the two most important “new spiritual authorities” guiding foreigners to join the Islamic State. For three years he was a televangelist on Iqraa TV in Cairo, but he left after the station objected to his frequent calls to establish a caliphate. Now he preaches on Facebook and Twitter. Related Story Pilgrims to the Islamic State Cerantonio—a big, friendly man with a bookish demeanor—told me he blanches at beheading videos. He hates seeing the violence, even though supporters of the Islamic State are required to endorse it. (He speaks out, controversially among jihadists, against suicide bombing, on the grounds that God forbids suicide; he differs from the Islamic State on a few other points as well.) He has the kind of unkempt facial hair one sees on certain overgrown fans of The Lord of the Rings, and his obsession with Islamic apocalypticism felt familiar. He seemed to be living out a drama that looks, from an outsider’s perspective, like a medieval fantasy novel, only with real blood. Last June, Cerantonio and his wife tried to emigrate—he wouldn’t say to where (“It’s illegal to go to Syria,” he said cagily)—but they were caught en route, in the Philippines, and he was deported back to Australia for overstaying his visa. Australia has criminalized attempts to join or travel to the Islamic State, and has confiscated Cerantonio’s passport. He is stuck in Melbourne, where he is well known to the local constabulary. If Cerantonio were caught facilitating the movement of individuals to the Islamic State, he would be imprisoned. So far, though, he is free—a technically unaffiliated ideologue who nonetheless speaks with what other jihadists have taken to be a reliable voice on matters of the Islamic State’s doctrine. 
 
 We met for lunch in Footscray, a dense, multicultural Melbourne suburb that’s home to Lonely Planet, the travel-guide publisher. Cerantonio grew up there in a half-Irish, half-Calabrian family. On a typical street one can find African restaurants, Vietnamese shops, and young Arabs walking around in the Salafi uniform of scraggly beard, long shirt, and trousers ending halfway down the calves. Cerantonio explained the joy he felt when Baghdadi was declared the caliph on June 29—and the sudden, magnetic attraction that Mesopotamia began to exert on him and his friends. “I was in a hotel [in the Philippines], and I saw the declaration on television,” he told me. “And I was just amazed, and I’m like, Why am I stuck here in this bloody room?” The last caliphate was the Ottoman empire, which reached its peak in the 16th century and then experienced a long decline, until the founder of the Republic of Turkey, Mustafa Kemal Atatürk, euthanized it in 1924. But Cerantonio, like many supporters of the Islamic State, doesn’t acknowledge that caliphate as legitimate, because it didn’t fully enforce Islamic law, which requires stonings and slavery and amputations, and because its caliphs were not descended from the tribe of the Prophet, the Quraysh. Baghdadi spoke at length of the importance of the caliphate in his Mosul sermon. He said that to revive the institution of the caliphate—which had not functioned except in name for about 1,000 years—was a communal obligation. He and his loyalists had “hastened to declare the caliphate and place an imam” at its head, he said. “This is a duty upon the Muslims—a duty that has been lost for centuries … The Muslims sin by losing it, and they must always seek to establish it.” Like bin Laden before him, Baghdadi spoke floridly, with frequent scriptural allusion and command of classical rhetoric. Unlike bin Laden, and unlike those false caliphs of the Ottoman empire, he is Qurayshi. 
 
 The caliphate, Cerantonio told me, is not just a political entity but also a vehicle for salvation. Islamic State propaganda regularly reports the pledges of baya’a (allegiance) rolling in from jihadist groups across the Muslim world. Cerantonio quoted a Prophetic saying, that to die without pledging allegiance is to die jahil (ignorant) and therefore die a “death of disbelief.” Consider how Muslims (or, for that matter, Christians) imagine God deals with the souls of people who die without learning about the one true religion. They are neither obviously saved nor definitively condemned. Similarly, Cerantonio said, the Muslim who acknowledges one omnipotent god and prays, but who dies without pledging himself to a valid caliph and incurring the obligations of that oath, has failed to live a fully Islamic life. I pointed out that this means the vast majority of Muslims in history, and all who passed away between 1924 and 2014, died a death of disbelief. Cerantonio nodded gravely. “I would go so far as to say that Islam has been reestablished” by the caliphate. Related Story ISIS and the Foreign-Fighter Phenomenon I asked him about his own baya’a, and he quickly corrected me: “I didn’t say that I’d pledged allegiance.” Under Australian law, he reminded me, giving baya’a to the Islamic State was illegal. “But I agree that [Baghdadi] fulfills the requirements,” he continued. “I’m just going to wink at you, and you take that to mean whatever you want.” 
 
 To be the caliph, one must meet conditions outlined in Sunni law—being a Muslim adult man of Quraysh descent; exhibiting moral probity and physical and mental integrity; and having ’amr, or authority. This last criterion, Cerantonio said, is the hardest to fulfill, and requires that the caliph have territory in which he can enforce Islamic law. Baghdadi’s Islamic State achieved that long before June 29, Cerantonio said, and as soon as it did, a Western convert within the group’s ranks—Cerantonio described him as “something of a leader”—began murmuring about the religious obligation to declare a caliphate. He and others spoke quietly to those in power and told them that further delay would be sinful. Social-media posts from the Islamic State suggest that executions happen more or less continually. Cerantonio said a faction arose that was prepared to make war on Baghdadi’s group if it delayed any further. They prepared a letter to various powerful members of ISIS, airing their displeasure at the failure to appoint a caliph, but were pacified by Adnani, the spokesman, who let them in on a secret—that a caliphate had already been declared, long before the public announcement. They had their legitimate caliph, and at that point there was only one option. “If he’s legitimate,” Cerantonio said, “you must give him the baya’a.” Related Story How ISIS Territory Has Changed Since the U.S. Bombing Campaign Began After Baghdadi’s July sermon, a stream of jihadists began flowing daily into Syria with renewed motivation. Jürgen Todenhöfer, a German author and former politician who visited the Islamic State in December, reported the arrival of 100 fighters at one Turkish-border recruitment station in just two days. His report, among others, suggests a still-steady inflow of foreigners, ready to give up everything at home for a shot at paradise in the worst place on Earth. 
 
 In London, a week before my meal with Cerantonio, I met with three ex-members of a banned Islamist group called Al Muhajiroun (The Emigrants): Anjem Choudary, Abu Baraa, and Abdul Muhid. They all expressed desire to emigrate to the Islamic State, as many of their colleagues already had, but the authorities had confiscated their passports. Like Cerantonio, they regarded the caliphate as the only righteous government on Earth, though none would confess having pledged allegiance. Their principal goal in meeting me was to explain what the Islamic State stands for, and how its policies reflect God’s law. 
 
 Choudary, 48, is the group’s former leader. He frequently appears on cable news, as one of the few people producers can book who will defend the Islamic State vociferously, until his mike is cut. He has a reputation in the United Kingdom as a loathsome blowhard, but he and his disciples sincerely believe in the Islamic State and, on matters of doctrine, speak in its voice. Choudary and the others feature prominently in the Twitter feeds of Islamic State residents, and Abu Baraa maintains a YouTube channel to answer questions about Sharia. Since September, authorities have been investigating the three men on suspicion of supporting terrorism. Because of this investigation, they had to meet me separately: communication among them would have violated the terms of their bail. But speaking with them felt like speaking with the same person wearing different masks. Choudary met me in a candy shop in the East London suburb of Ilford. He was dressed smartly, in a crisp blue tunic reaching nearly to his ankles, and sipped a Red Bull while we talked. Before the caliphate, “maybe 85 percent of the Sharia was absent from our lives,” Choudary told me. “These laws are in abeyance until we have khilafa”—a caliphate—“and now we have one.” Without a caliphate, for example, individual vigilantes are not obliged to amputate the hands of thieves they catch in the act. But create a caliphate, and this law, along with a huge body of other jurisprudence, suddenly awakens. In theory, all Muslims are obliged to immigrate to the territory where the caliph is applying these laws. One of Choudary’s prize students, a convert from Hinduism named Abu Rumaysah, evaded police to bring his family of five from London to Syria in November. On the day I met Choudary, Abu Rumaysah tweeted out a picture of himself with a Kalashnikov in one arm and his newborn son in the other. Hashtag: #GenerationKhilafah. 
 
 The caliph is required to implement Sharia. Any deviation will compel those who have pledged allegiance to inform the caliph in private of his error and, in extreme cases, to excommunicate and replace him if he persists. (“I have been plagued with this great matter, plagued with this responsibility, and it is a heavy responsibility,” Baghdadi said in his sermon.) In return, the caliph commands obedience—and those who persist in supporting non-Muslim governments, after being duly warned and educated about their sin, are considered apostates. Related Story How ISIS Got Its Flag Choudary said Sharia has been misunderstood because of its incomplete application by regimes such as Saudi Arabia, which does behead murderers and cut off thieves’ hands. “The problem,” he explained, “is that when places like Saudi Arabia just implement the penal code, and don’t provide the social and economic justice of the Sharia—the whole package—they simply engender hatred toward the Sharia.” That whole package, he said, would include free housing, food, and clothing for all, though of course anyone who wished to enrich himself with work could do so. Abdul Muhid, 32, continued along these lines. He was dressed in mujahideen chic when I met him at a local restaurant: scruffy beard, Afghan cap, and a wallet outside of his clothes, attached with what looked like a shoulder holster. When we sat down, he was eager to discuss welfare. The Islamic State may have medieval-style punishments for moral crimes (lashes for boozing or fornication, stoning for adultery), but its social-welfare program is, at least in some aspects, progressive to a degree that would please an MSNBC pundit. Health care, he said, is free. (“Isn’t it free in Britain, too?,” I asked. “Not really,” he said. “Some procedures aren’t covered, such as vision.”) This provision of social welfare was not, he said, a policy choice of the Islamic State, but a policy obligation inherent in God’s law. 
 
 III. The Apocalypse All Muslims acknowledge that God is the only one who knows the future. But they also agree that he has offered us a peek at it, in the Koran and in narrations of the Prophet. The Islamic State differs from nearly every other current jihadist movement in believing that it is written into God’s script as a central character. It is in this casting that the Islamic State is most boldly distinctive from its predecessors, and clearest in the religious nature of its mission. 
 
 In broad strokes, al-Qaeda acts like an underground political movement, with worldly goals in sight at all times—the expulsion of non-Muslims from the Arabian peninsula, the abolishment of the state of Israel, the end of support for dictatorships in Muslim lands. The Islamic State has its share of worldly concerns (including, in the places it controls, collecting garbage and keeping the water running), but the End of Days is a leitmotif of its propaganda. Bin Laden rarely mentioned the apocalypse, and when he did, he seemed to presume that he would be long dead when the glorious moment of divine comeuppance finally arrived. “Bin Laden and Zawahiri are from elite Sunni families who look down on this kind of speculation and think it’s something the masses engage in,” says Will McCants of the Brookings Institution, who is writing a book about the Islamic State’s apocalyptic thought. During the last years of the U.S. occupation of Iraq, the Islamic State’s immediate founding fathers, by contrast, saw signs of the end times everywhere. They were anticipating, within a year, the arrival of the Mahdi—a messianic figure destined to lead the Muslims to victory before the end of the world. McCants says a prominent Islamist in Iraq approached bin Laden in 2008 to warn him that the group was being led by millenarians who were “talking all the time about the Mahdi and making strategic decisions” based on when they thought the Mahdi was going to arrive. “Al-Qaeda had to write to [these leaders] to say ‘Cut it out.’ ” 
 
 For certain true believers—the kind who long for epic good-versus-evil battles—visions of apocalyptic bloodbaths fulfill a deep psychological need. Of the Islamic State supporters I met, Musa Cerantonio, the Australian, expressed the deepest interest in the apocalypse and how the remaining days of the Islamic State—and the world—might look. Parts of that prediction are original to him, and do not yet have the status of doctrine. But other parts are based on mainstream Sunni sources and appear all over the Islamic State’s propaganda. These include the belief that there will be only 12 legitimate caliphs, and Baghdadi is the eighth; that the armies of Rome will mass to meet the armies of Islam in northern Syria; and that Islam’s final showdown with an anti-Messiah will occur in Jerusalem after a period of renewed Islamic conquest. The Islamic State has attached great importance to the Syrian city of Dabiq, near Aleppo. It named its propaganda magazine after the town, and celebrated madly when (at great cost) it conquered Dabiq’s strategically unimportant plains. It is here, the Prophet reportedly said, that the armies of Rome will set up their camp. The armies of Islam will meet them, and Dabiq will be Rome’s Waterloo or its Antietam. Related Story The Islamic State of Iraq and Syria Has a Consumer Protection Office “Dabiq is basically all farmland,” one Islamic State supporter recently tweeted. “You could imagine large battles taking place there.” The Islamic State’s propagandists drool with anticipation of this event, and constantly imply that it will come soon. The state’s magazine quotes Zarqawi as saying, “The spark has been lit here in Iraq, and its heat will continue to intensify … until it burns the crusader armies in Dabiq.” A recent propaganda video shows clips from Hollywood war movies set in medieval times—perhaps because many of the prophecies specify that the armies will be on horseback or carrying ancient weapons. 
 
 Now that it has taken Dabiq, the Islamic State awaits the arrival of an enemy army there, whose defeat will initiate the countdown to the apocalypse. Western media frequently miss references to Dabiq in the Islamic State’s videos, and focus instead on lurid scenes of beheading. “Here we are, burying the first American crusader in Dabiq, eagerly waiting for the remainder of your armies to arrive,” said a masked executioner in a November video, showing the severed head of Peter (Abdul Rahman) Kassig, the aid worker who’d been held captive for more than a year. During fighting in Iraq in December, after mujahideen (perhaps inaccurately) reported having seen American soldiers in battle, Islamic State Twitter accounts erupted in spasms of pleasure, like overenthusiastic hosts or hostesses upon the arrival of the first guests at a party. The Prophetic narration that foretells the Dabiq battle refers to the enemy as Rome. Who “Rome” is, now that the pope has no army, remains a matter of debate. But Cerantonio makes a case that Rome meant the Eastern Roman empire, which had its capital in what is now Istanbul. We should think of Rome as the Republic of Turkey—the same republic that ended the last self-identified caliphate, 90 years ago. Other Islamic State sources suggest that Rome might mean any infidel army, and the Americans will do nicely. After mujahideen reported having seen American soldiers in battle, Islamic State Twitter accounts erupted in spasms of pleasure, like overenthusiastic hosts upon the arrival of the first guests at a party. After its battle in Dabiq, Cerantonio said, the caliphate will expand and sack Istanbul. Some believe it will then cover the entire Earth, but Cerantonio suggested its tide may never reach beyond the Bosporus. An anti-Messiah, known in Muslim apocalyptic literature as Dajjal, will come from the Khorasan region of eastern Iran and kill a vast number of the caliphate’s fighters, until just 5,000 remain, cornered in Jerusalem. Just as Dajjal prepares to finish them off, Jesus—the second-most-revered prophet in Islam—will return to Earth, spear Dajjal, and lead the Muslims to victory. ||||| Updated January 25, 2017 At dawn on a warm September morning in 2013, a minivan pulled up to a shattered villa in the town of Azaz, Syria. A long-bearded 29-year-old white man emerged from the building, along with his pregnant British wife and their three children, ages 8, 4, and almost 2. They had been in Syria for only about a month this time. The kids were sick and malnourished. The border they’d crossed from Turkey into Syria was minutes away, but the passage back was no longer safe. They clambered into the minivan, sitting on sheepskins draped on the floor—there were no seats—and the driver took them two hours east through a ravaged landscape, eventually stopping at a place where the family might slip into Turkey undetected. They disembarked amid a grove of thorny trees. Signs warned of land mines. The border itself was more than an hour’s walk away, through the desert. They’d forgotten to bring water. Tania dragged the puking kids along; Yahya carried a suitcase and a stroller. Midway, Tania had contractions, although she was still several months from her due date. They continued on. At the border itself, while the family squeezed through the barbed wire, a sniper’s bullets kicked up dirt nearby. 
 
 Yahya had arranged for a human trafficker to meet them, and when the trafficker’s truck arrived, Yahya pressed a few hundred dollars into the man’s hand. Yahya and Tania had been married for 10 years, but they did not say goodbye. Satisfied that his family would not die, Yahya turned and ran across the border, back into Syria—again under gunfire—without even a wave. The trafficker drove Tania and the kids a short distance into Turkey, then dropped them by the roadside without food or water and sped off. Tania carried the children and luggage toward the nearest town. The day ended with the intercession of a stranger on a motorcycle, who helped carry their things to a bus station. Tania started to leak amniotic fluid due to the journey, and she spent the next weeks recovering in Istanbul, and then with family in London. Six months pregnant, she weighed 96 pounds. As his family traveled to London, relieved to have escaped the worst place on Earth, Yahya felt relief of his own—he could now pursue his dreams unencumbered by a wife and children. He felt liberated. He carried visions of the caliphate yet to be declared, and ideas for how to shape it. These thoughts were not idle. Yahya, by then, had a small but influential following, and his calm erudition had won him the respect that his teachers and parents had withheld during his youth. His own destiny seemed to be converging with that of the world’s. It was the best day of his life. 
 
 I first heard the name Yahya Abu Hassan in 2014, while reporting on an article for this magazine about the rise of the Islamic State. I was in a suburb of Melbourne, talking with Musa Cerantonio, an Australian convert to Islam who has served as an unofficial spiritual guide to many English-speaking followers of the group, about its history and theology. (He is now in jail, charged with attempting to travel to Islamic State territory.) In our earliest conversations, Cerantonio mentioned a fellow convert—a “teacher” or “leader,” he called him—who had done much to prepare Muslims for the religious obligations that would kick in once a caliphate had been established. Cerantonio spoke of his teacher with awe. Yahya was deeply devoted to the idea of the caliphate, he said, and showed a staggering mastery of Islamic law and classical Arabic language and literature. Jihadists in Syria knew him by reputation, and they honored him when they met him. Cerantonio said that in early 2014, Yahya had pressed the leaders of what was then the Islamic State of Iraq and al-Sham (isis) to declare a caliphate. He began preaching that the conditions for the declaration of a valid caliphate had been met—the group held and governed territory, and its leader, Abu Bakr al-Baghdadi, was a physically and mentally fit male of Qurayshi descent, capable of ruling according to Sharia. Delaying further would mean disregarding a fundamental obligation of Islam. Yahya had developed a relationship with Abu Muhammad al-Adnani, the group’s spokesman, chief strategist, and director of foreign terror operations. “Yahya was like this with Adnani,” Cerantonio told me, pressing his fingers together. Yahya met with Adnani near Aleppo and warned him that Baghdadi would be in a state of sin if he did not promote himself to caliph immediately. Yahya and his allies had prepared but not yet sent a letter to the emirs of the isis provinces, airing their displeasure at his failure to do so. They were ready to make war on Baghdadi if he delayed further. Adnani replied with good news—that a caliphate had already been declared secretly, months before, and that it would soon be publicly announced. 
 
 Yahya shared the update with Cerantonio, who leaked word of the caliphate declaration on Facebook. Within weeks the official public declaration took place in Mosul, Iraq, and Yahya immediately pledged himself to Baghdadi, urging others to do likewise. The figure of Yahya—an English-speaking convert within isis with powerful connections and the cojones to challenge Baghdadi to a death match—intrigued me. But Cerantonio didn’t elaborate on his identity and referred to him only by an alias, in the traditional Arabic style, with his first name and the name of his firstborn: Yahya, father of Hassan. He said Yahya was a fellow Dhahiri—a member of an obscure, ultra-literalist legal school that had enjoyed a sort of revival within the Islamic State. He didn’t, or wouldn’t, say more. I wrote down the name and committed to investigating Yahya later. Americans are known to have traveled to Syria as jihadists. Most are knuckleheads. Yahya, it seemed, was unique. Soon enough, I began collecting clues to his identity. In early 2015, a pro–Islamic State Twitter user (his handle identified him as a “swordsman”) wrote to me and advised me to contact “Abu Yahya” to learn more about the group. The name resembled Yahya Abu Hassan’s closely enough to lead me to believe he was the same person Cerantonio had mentioned. The Twitter user claimed Yahya was Greek. “He is on the field”—in the war zone—“and part of the IS,” the swordsman wrote. “A great mind and a trustworthy student.” 
 
 He then shared a link to a website that featured a collection of Dhahiri writings by Cerantonio and a few others—including a “Yahya al-Bahrumi.” In fluent Arabic and English, Yahya wrote prolifically about many jihadist subjects. He projected calm even in his most grotesque opinions, and wore the label irhabi (“terrorist”) with pride: This word (“terrorist”) has also been cast as an insult and has been received as such. But irhab [“terror”] itself is something notable scholars have declared obligatory and supported verbatim by the Qur’an itself. He called for emigration to lands where Sharia would be fully enforced, and wrote that choosing not to emigrate was a form of apostasy: Call me extreme, but I would imagine that all of those who willingly choose to live among those with whom Muslims are at war are themselves at war with Muslims—and as such, are not actually Muslims. 
 
 
 
 Get out if you can—not only in support of your brothers and sisters whom your taxes have been killing, but also to protect yourselves from the punishment Allah has ordained for those who betray the nation. He called for Muslims to hate, fight, and kill infidels—among whom, he said, were many so-called Muslims who nullified their faith by neglecting prayer, deviating from the narrow literalism of his interpretation of scripture, or, in the case of rulers, not instituting the brutal system of justice for which the Islamic State was then becoming famous. 
 
 In dozens of articles posted over several years, Yahya demonstrated knowledge of classical Arabic—the notoriously difficult language of educated religious speech—and familiarity with Islamic sources and history. His Arabic was stunning even to Cerantonio, an extremely self-confident religious autodidact. Cerantonio told me that another Muslim in their internet discussion group had once challenged a theological point Yahya had made. “Then Yahya did something that shocked us all,” Cerantonio said. “He responded to the guy in traditional Arabic poetry that he devised off the top of his head, using the guy’s name in the poetry, explaining the situation, and answering his objections.” For any claim, it seemed, Yahya could instantly spout textual support, and confronted with any counterclaim, he could undercut the argument with a sweep of the leg. The website the swordsman had pointed me to included a narrative biography and a small photo of Yahya, its founder. The picture showed a bearded, bespectacled young man with a Kalashnikov over his shoulder. He was dressed for cold weather, as if in preparation for a night raid or patrol. When I saw him, I wondered when I had last seen someone looking so content. As for the biography itself, nearly every word showed signs of careful selection, including his name, Bahrumi, a portmanteau of the Arabic words bahr (“sea”) and rumi (“Roman”). Many jihadists construct a nom de guerre from their first name and their national origin. He called himself Yahya of the Roman Sea, or Yahya the Mediterranean. 
 
 The biography continued: His roots are from the island of Crete in the Roman sea (Bahr al-Rūm). Born in 1404 [ a . d . 1983–84] and raised as a Nazarene [Christian], Yahya then entered Islam in 1422 [ a . d . 2001–02]. He traveled seeking knowledge and work in the path of Allah until Allah granted him hijrah [migration] to Sham. He now resides in the countryside of Aleppo. Now I thought I had enough data to narrow down his identity: a philologically inclined Cretan jihadist convert not just to Islam but to Dhahirism, a minuscule legal school. The list of candidates could not be long. Many converts choose Arabic names that are the equivalent of their birth names. Yahya is Arabic for John, in English, or Ioannis in Greek, so I began searching online for Dhahiris with these names. In a German-language jihadist chat room, I found a reference to “Ioannis Georgilakis,” and here the trail began to sizzle under my feet. Georgilakis’s Facebook page showed photos of the same hirsute young man with glasses, dressed in Muslim garments and playing with his kids. As I looked at his Facebook page, I began to wonder whether the Greek was an affectation. Many of his Facebook friends were English speakers, and few were Greek. Georgilakis isn’t an especially common surname, and given Yahya’s apparent creativity in self-naming, I tried a few permutations, including the English John and the vanilla, non-Cretan Greek version of Georgilakis, which would be Georgelas. 
 
 One of the first hits on Google for John Georgelas was an August 15, 2006, press release from the Department of Justice. “Supporter of Pro-Jihad Website Sentenced to 34 Months,” it crowed. At the time of his conviction, he lived in North Texas, near Plano, 20 minutes’ drive from the house where I grew up. American Muslims are rare in the Islamic State: Only 53 are publicly known to have traveled to Syria as jihadists, according to Seamus Hughes, the deputy director of George Washington University’s Program on Extremism. (The United States has stopped more than 100 others in the process of preparing to travel, or to act on behalf of the Islamic State in America.) Hughes, a former Senate staffer, has meticulously cataloged the Americans who have made it to Syria, and places nearly all of them in the category of “knuckleheads”—brawny idiots with little hope of understanding a discussion of Islamic theology. Many have by now fulfilled their dream of battlefield death; all that remains of them is a martyrdom notice, posted like a headstone, on their Facebook page. However canny the Islamic State’s internet-based recruiting, a personal touch remains crucial to fully radicalizing most targets and signing up new terrorists. In the United Kingdom, more than 100 fighters have waged jihad after contact with a group called Al Muhajiroun; in Belgium, Sharia4Belgium has recruited numerous Islamic State fighters. But in the United States, groups like these exist only in the fever dreams of Islamophobes. 
 
 Fewer than 20 percent of the Americans in the Islamic State are known to be converts to Islam, and many have long-standing family connections with other countries—long periods of residence in Kuwait, say, or ties to the Somali tribes of their parents. They do not, as a rule, ascend to high positions in the Islamic State’s organization. One Bosnian American, Abdullah Pazara, parlayed Serbian military training into command of an isis tank battalion. But even Pazara (who died in 2014) was relatively obscure and uncelebrated. In the United States, his most glorious achievement was owning a barely profitable trucking company. Not all recruits are stupid. At least three have a college education and, according to friends and family, good academic records and habits. The smart ones, though, have in effect renounced their learning in favor of the greater glory of jihad. Having made it onto the dean’s list for a degree in computer science counts neither for nor against you if your goal is to explode in a crowd of apostates. Yahya, it seemed to me, was unique. He in some ways resembled his fellow Americans in Syria: He went to fight, and he would have welcomed a battlefield death if God had willed it. But he was no mere foot soldier; his religious scholarship, connections, and standing distinguished him—even if I didn’t then understand their full extent. I wanted to know more. Plano is a short drive from downtown Dallas, toward the Oklahoma border, a flatland sprouting subdivisions watered by money from the region’s burgeoning tech sector. Shortly after his probation expired, John Georgelas had posted a résumé online listing as his address an elegant brick house with white Doric columns, a small portico, and a circular driveway. In August 2015, when I first drove up, I could hear the happiness of children. I saw a boy, who looked about 10, bouncing a basketball in the driveway and two others playing nearby; they were about the same ages as the kids in the Facebook photos. As I approached the front door, I spied a yellow-ribbon decal (“We support our troops”) in the window, and behind it a foyer, tidy and richly decorated, and a piano festooned with family photos. 
 
 The man who answered the door was Timothy Georgelas, John’s father and the owner (with his wife, John’s mother, Martha) of the house. Both parents are Americans of Greek ancestry. Tim is a West Point graduate and a physician. He has a full head of gray hair and soft features that betray no sign of the stress of having raised an Islamic State terrorist. He has, however, no illusions about the life his son has chosen. “He and John are enemies,” I was told by someone who knows them both—“until the Day of Judgment.” Tim wore shorts and a T-shirt, and a crisp draft of air conditioning escaped as he said good morning. When I told him I had come to ask about John, he stepped outside and shut the door as if to seal off the house from his son’s name. He slumped in a white wicker chair by the front door, and with a reluctant gesture, he invited me to sit across from him. He stared at the magnolia tree in the front yard and said nothing. I told him what I knew—that his son, John, was Yahya. Tim sat, lips pursed, and with a shake of his head began to speak. “Every step of his life he’s made the wrong decisions, from high school onward,” Tim told me. “It is beyond me to understand why he threw what he had away.” Two of Yahya’s sisters have earned advanced degrees, he added, as if to demonstrate that it wasn’t failed parenting that led his only son to drop out of school, wage holy war, and plot mass murder. 
 
 “He was always the youngest kid in the class, and always a follower,” Tim said. “I have bailed him out so many times—financially, in circumstances with his wife and kids, you name it. I always pick up the wreckage.” The Yahya Tim described to me was a sad figure, a sheep who had strayed into a wicked flock. Above all, he was easily manipulated. This, for me, was another puzzle. The Yahya I had encountered online, and the one Musa Cerantonio described, was nothing like a sheep, and no pathetic follower. He was not the boy his father described. At some point, Yahya had shape-shifted into a wolf, into a leader of men. In December 1983, John Thomas Georgelas was born into a wealthy family with a long military tradition. His grandfather Colonel John Georgelas was wounded twice in the Second World War and worked for the Joint Chiefs of Staff. Tim Georgelas spent three years in the U.S. Army, then accepted an Air Force commission to attend medical school. He retired as a colonel in 2001, and now practices radiology in a north-Dallas breast-imaging clinic. He is politically conservative, as is Martha, his short, dark-haired wife, whose Facebook cover photo shows her standing proudly in front of the George W. Bush Presidential Center, near downtown Dallas. The Georgelases moved frequently during John’s youth, as Tim’s military assignments required. John entered school at the age of 4, while the family was living in England, and he was young and small for his class. He was sickly—he grew benign tumors and had brittle bones—and his infirmities may have pushed him toward religion. When he was 11, his leg shattered, and he spent a long period out of school, recuperating. Lonely and depressed, his mind turned to God in idle moments, and he became attached to the Greek Orthodox Church. Wheelchair-bound, he hounded his family into attending services more regularly. Among his spiritual mentors was a clergyman who encouraged John to hate and distrust Muslims, with an intensity that would later change its polarity. (A family member calls John’s attitude one of “righteous fury, jacked up with certainty”—a bright-burning sanctimony that has been consistent across his religious transformations.) 
 
 As the family’s male heir, John enjoyed a special status in the Georgelas patriarchy. With that status came expectations, and therefore disappointment when it became clear he was unsuited for a soldier’s life. His body refused to grow into robust, battle-ready form. Tim is tall, a former high-school quarterback, but John was shorter, his torso tending to pudge. His temperament wasn’t suited to military discipline. When he returned to school after his leg injury, he had little interest in academic achievement or rule-following. His father tried repeatedly to correct his behavior and failed. (This account is drawn from sources close to John, including family members, co-workers, friends, and correctional officers.) When John uttered the Muslim declaration of faith, the ashes of the World Trade Center were barely cool. Nor did he fit in well with his peers. He gravitated toward the skateboard set, and he didn’t date much, if at all. (One acquaintance told me, “If you put a million bucks on the table and told him to use it to go get laid, he couldn’t do it to save his life.”) Like many a military brat before him, John experimented with the counterculture. He smoked pot, dropped acid, and ate magic mushrooms. He hated his father for punishing his drug use and hated the U.S. government for criminalizing it. By the time he graduated from high school, his primary interests were computer hacking, skateboarding, and the voracious consumption of psychedelics. His grades were miserable, Tim says, but his standardized-test scores were better than those of his high-achieving sisters. John ended up studying philosophy at the College Station branch of Blinn College, an open-admission junior college in central Texas. He passed only a few classes. 
 
 In a class on world religions at Blinn, the instructor’s cursory lecture on Islam annoyed him, so John sought more information from local Muslims. Curiosity turned to something more, as he discovered that Muslims were not the demons he had been led to expect them to be. A few days before Thanksgiving 2001, on the first day of Ramadan, John converted at a mosque in College Station frequented by foreign students from Texas A&M. Whether the conversion was meant to spite his parents or whether spite was just an ancillary benefit of his spiritual salvation, it is not possible to say. But the timing is suggestive. When John uttered the Muslim declaration of faith, the ashes of the World Trade Center were barely cool. Anti-Muslim sentiment in America was reaching new highs, and in central Texas, conversion to Islam would have been a singular act of rebellion. John’s parents found his conversion to be a sign of mental weakness. “Every university town in this country has a mosque for one reason,” Tim told me. “Kids are away from home for the first time, vulnerable and subject to influence. They hear the message and they’re hooked, and that’s what happened to John.” John took the name Yahya, and sold his pickup truck to buy a plane ticket. In December 2001, the family received an email from Yahya announcing that he was in Damascus learning Arabic. 
 
 Western jihadists find their way to violence many different ways, but they often match a profile. And that profile fit John like a wet suit. He came from an upper-middle-class family. He squandered opportunities commensurate with his innate talent; he recognized that he would not excel in the fields chosen or glorified by his parents and authority figures. Often, a personal crisis—a death in the family, a near-death experience of one’s own—triggers existential contemplation, leading to religious exploration; in John’s case, his childhood frailty might have filled that role. Jihadists are also overwhelmingly left-brained, quantitative-analytic types. Diego Gambetta of the European University Institute and Steffen Hertog of the London School of Economics have noted a preponderance of former engineering students among jihadists; they suggest that the mental style of that discipline disposes certain people toward jihadism. As a teen, John had taught himself to program. His computers ran the Linux operating system, not the Windows or Mac software favored by the masses. Years later, after he had become a full-blown jihadist, he would share a line of C++ code on his website, a geeky statement of his own hard-line stance: if (1+1+1 != 1 && 1 == 1) return true; else die(); Translation: If you believe the Christian Trinity (“1+1+1”) is not really monotheistic (“!= 1”), and if you believe in the unity of God (“1 == 1”), then great. Otherwise: Die. 
 
 Despite these binary inclinations, upon his arrival in Damascus Yahya envisioned himself as a Sufi, a Muslim mystic who sought oneness with God through poetry, perhaps, or dance or song, and who could countenance a shaded, or nuanced, version of Islam. That posture may have been a holdover from his counterculture teens. Gradually, though, under the influence of British Muslims who were more rigid in their approach to the faith, he became jihad-curious. They persuaded him to follow a bin-Ladenist approach, hostile to Sufism, instead. Yahya soon surpassed them in intolerance. To his jihadism he added general displeasure with the hierarchy of scholarly authority in mainstream religion. He objected to mainstream imams’ telling him to trust the words of scholars and not to attempt his own interpretation of scripture and law. Muslim laymen are generally advised not to derive legal rulings on their own, and to follow more-experienced scholars. But Yahya maintained a typically American can-do attitude toward his religion, similar to the one many Texans adopt toward their trucks: If he couldn’t understand or fix it himself, it didn’t feel like his. He acquired The Hans Wehr Dictionary of Modern Written Arabic, a cuboid volume that is the standard Arabic-English reference work. It is not meant to be read through. The typical student of Arabic keeps the Hans Wehr on a corner of his desk and consults it as needed for the rest of his natural life. Yahya memorized it in six months. Then, as a chaser, he memorized Kitab al-Ayn, the eighth-century Arabic dictionary by al-Khalil al-Farahidi. He wandered through Damascus, chatting up everyone and learning classical Arabic to a level of proficiency rarely achieved even by educated native Arabic speakers. 
 
 He drifted further from his parents and sisters. Later, when counseling other Muslims about how much effort to put into proselytization at home versus heading directly to the Islamic State, Yahya wrote: What about those [Muslims] who are trying to work on their families, but their families insist on kufr [disbelief in Islam]? Should they wait their whole lives in patience, trying to guide someone whom Allah has not chosen for guidance, or should they move on and help their true family: the Muslims? Yahya met his wife in 2003 on a Muslim matrimonial site. Tania was born in London in 1983 to Bengali British parents. It was almost as if they had shared the same life, before even being introduced. Like Yahya, Tania grew up riddled with benign tumors and incorrigibly rebellious. She tormented her parents by practicing, with alarming vigor, the religion they had neglected in the pursuit of an assimilated English middle-class existence. She was a pretty girl, a petite firecracker. But her mischief was not of the usual variety, like dating boys her parents didn’t approve of. When her parents suggested that she try to meet boys, Tania hissed “Muslims don’t date.” She had a type: Her heartthrob was John Walker Lindh, the American who fought for the Taliban in 2001. She swore that until marriage no strange man would know anything more of her physical appearance than its cloaked outline, and by her late teens she was draping herself in a full-body covering, or jilbab. She fantasized about packing a bomb under it. At 19, she married Yahya. Yahya and Tania lied to anyone who inquired about their activities. When Syrian government spies started asking neighbors about them, they moved on. After meeting online, Yahya and Tania fell in love fast, and just as couples bond over Netflix or jogging or cooking, they bonded over jihad and a shared capacity for bad decisions. After a month of digital flirtation, Yahya flew to London, and they met in person on March 15, 2003. Within three days they married secretly, then left for Texas. They settled in College Station and partook of the pleasures of freedom, young love, and independence from family. They lived cheaply and happily, embracing as their community the foreign students at the mosque where Yahya had converted. The mosque threw them a wedding party, and rich Gulf Arabs who lived near the university kicked in money to support Yahya’s continued study of Islam. 
 
 The couple indulged, too, in their other shared passion: getting high. Islamic orthodoxy considers cannabis an intoxicant, and therefore forbidden. But Yahya’s practice of Islam was unconventional even then. In a historical essay titled “Cannabis,” heavily footnoted with classical Arabic sources, he made the Islamic case for pot. There was evidence, he wrote, that early Islamic leaders had taxed hemp seeds. Since Muslims generally cannot tax forbidden substances, such as pork or alcohol, Yahya reasoned, they must have considered pot permissible. As for psilocybin: Yahya cited an obscure hadith (a report of the sayings and actions of Muhammad) that he said described Muhammad’s having descended from a mountain after meditation and extolling the medicinal properties of mushrooms—particularly as a cure for diseases of the eye. Yahya and Tania took this to mean that God had sanctioned the ingestion of psychedelic mushrooms. So the young lovers blissed out under the Texas sky, shrooming after the example of the prophet himself. In late 2003, Yahya and Tania traveled to Damascus for an extended honeymoon, living there furtively and quietly associating with other jihadists. Their existence mirrored that of many young radical tumbleweeds of yesteryear: Black Panthers, Baader-Meinhof gangsters, fin de siècle anarchists. They dodged the authorities and lied to anyone who inquired about their activities. When Syrian government spies started asking neighbors about them, they moved on, settling briefly in a town selected because it was prophesied to be the headquarters of the prophet Jesus upon his return. They often quarreled. Still strong-willed, Tania wanted to obey only God. But God’s words were unequivocal: “Men are in charge over women,” says a Koranic verse. So for most of the 10 years before the founding of the Islamic State, Yahya maintained a Rasputinlike control over her. He hadn’t had much success finding social esteem in his prior life, but in Tania he found his first student. He mesmerized her with his confidence, and she repressed her own misgivings whenever she found herself questioning him. Tania has mild dyslexia; Yahya’s reading of Islamic texts convinced her, with his fluency and recall and breadth, that he could produce an unanswerable argument about any point on which she disagreed. She determined that Yahya was a genius with gifts God had denied her, and she accepted her place in the world of jihad: Service to Yahya was her ticket to heaven. She endorsed slavery, apocalypse, polygamy, and killing. She aspired to raise seven boys as holy warriors—one to conquer each continent. 
 
 From Syria they returned to London, where Yahya chose to follow a Jordanian known as Abu Issa. He had allegedly fought the Soviets in Afghanistan in the 1980s, and on April 3, 1993, his followers there swore loyalty to him and created what the French scholar Kévin Jackson calls “the forgotten caliphate,” an unsuccessful precursor of the Islamic State. Abu Issa declared himself caliph and ruled a small portion of Afghanistan’s Kunar province in the mid-to-late 1990s. There he implemented many practices that the Islamic State would later realize on a larger scale. The total area governed did not extend beyond a few small towns, and the local Afghans despised Abu Issa and his supporters. When Osama bin Laden came to Afghanistan in 1996, Abu Issa sent a message demanding his obedience. (There is no record of a reply.) In the late 1990s, when the Taliban took over Kunar province, Abu Issa and his followers relocated to London, and it was in that diminished state that Yahya and Tania first encountered them. For a while, Yahya had the jihadist-dork dream job of tutoring the caliph’s son in the subjects of computer hacking and martial arts. Ultimately Yahya and Abu Issa fell out over a dispute regarding interpretation of Islamic law. But during that period, Yahya nurtured an interest in the obligation to declare a caliphate and in Islamic literalism, both of which would drive him, in the end, back to Syria. 
 
 At a bookshop in London, he found a copy of the works of Ibn Hazm (994–1064), by far the greatest Dhahiri scholar. Dhahirism is the most binary and monochrome of Islamic legal schools. In some ways, it resembles the constitutional originalism of Clarence Thomas or Antonin Scalia: It drastically and pitilessly winnows down the sources of legal authority to the Koran, the sayings and actions of Muhammad, and the ironclad consensus of the prophet’s followers within his own lifetime. It refuses to accept new laws based on analogy to old ones, and it urges jurists and theologians to resist allegorical or figurative readings, and instead stick to rulings with plain textual support. The rejection of figurative readings, legal analogy, and other types of extended interpretation strikes most mainstream Muslim scholars as preposterous. But through Dhahiri eyes, scripture should simply be read like a manual—or like software. It is a legal and theological methodology that aligned well with Yahya’s left-brained, autodidactic disposition. In September 2004, Yahya and Tania returned to the United States, relying financially on Yahya’s parents. They settled briefly in Torrance, California, with Yahya hoping to find work as an imam. His jihadism disqualified him for mosque jobs, however, and increasingly the two sought only each other’s spiritual camaraderie. They stopped frequenting mosques altogether, on the grounds that they were dens of spies. When a SWAT team came to their house in Grapevine, Texas, early in the morning, Yahya and Tania were already awake for dawn prayers. In 2004, their first son was born in California. Yahya and Tania moved back to greater Dallas, and a year later, Yahya took a job as a data technician at Rackspace, a server company in Texas. At night, he cruised jihadist forums and offered tech support to Jihad Unspun, a Canada-based Islamist news site widely thought to be a recruiting ground for would-be terrorists. He also looked for ways to use his position at Rackspace to wage jihad. On April 8, 2006, he accessed the passwords of a client, the American Israel Public Affairs Committee, with the intention of hijacking its website. 
 
 As hacking jobs go, it was amateurish. Rackspace found out, and the FBI, aware of Yahya’s terror links, moved fast. When a swat team came to his house in Grapevine, Texas, early in the morning, he and Tania were already awake for dawn prayers. He surrendered peacefully and warned that a child was sleeping inside and that his wife needed to get dressed. The Department of Justice prosecuted him for hacking into a protected computer—this was the source of the press release I had found earlier—and a judge sentenced him to 34 months’ imprisonment. Prior to his arrest, he had planned to travel to Iraq to fight against the Americans, so prison may have saved his life. Yahya’s arrest caused marital friction of a new sort. With her husband in prison and studying Islamic texts full-time, Tania began asserting her independence. After receiving scowls from neighbors due to her Muslim dress, she told Yahya she planned to wear just a veil, and not a full-body cloak. Yahya, furious, demanded that she cover herself fully when she visited him in prison, to be sure no one would titter at the immodesty of the sheikh’s wife. (He had Muslim acquaintances in prison and was the most scholarly among them.) He told her to leave infidel America to join the group known as the Nigerian Taliban, a predecessor to Boko Haram. She refused and threatened divorce. But she didn’t leave him—even after he got out of prison and took a second wife, a Jamaican British friend of Tania’s. Tania did not approve, but she didn’t forbid the union. The bride still lived in London, and the groom could not travel without violating parole. Yahya investigated the Islamic legality of a marriage conducted across physical distance. He found precedent: Muhammad had married the widow of his brother-in-law when she was in Ethiopia and he was in Medina. Having ascertained the validity of marriage-by-telecom, Yahya and his second wife married over the phone, with Tania present and quietly fuming. (Yahya later divorced his second wife.) 
 
 About his crimes, he remained unrepentant. “He can justify anything he does, and he didn’t think he did anything wrong,” Tim says. “He is just full of himself.” During his parole, Yahya lived in Dallas and worked as an IT specialist for a shoe wholesaler. In August 2009, 10 months after he’d left prison, a second child arrived, another boy. The extended Georgelas family took a trip to Hawaii, and the couple came along. Tania stayed secluded, says one acquaintance, and Yahya harangued everyone about the virtues of Sharia law. But he mostly stayed quiet during that period. The family wondered whether he had mellowed, though Yahya’s colleagues at the shoe company report that he and Tania occasionally posted politically worrisome items on Facebook. Among their enthusiasms, at this point, was the libertarian Republican presidential candidate Ron Paul, whose antigovernment obsessions and isolationist foreign policy Yahya and Tania both found congenial. The prophet had endorsed the gold standard, and so did Paul. Yahya and Tania liked pot, and the Libertarians were the closest thing to an anti-prohibitionist party in the United States. And—finally—Paul’s foreign policy suggested a possible disengagement with Israel. “You guys (meaning Americans) need to stop supporting democracy, and just make Ron Paul your king,” Tania later wrote on Facebook, only half joking. Yahya wanted revolution. “Tyranny is here,” he replied, “and the Tree of Liberty is thirsty.” On October 1, 2011, Yahya’s parole expired, and he drove to the Dallas–Fort Worth airport with his wife and two children, a free man. He was leaving America—probably for good. “Muslims in America,” he wrote around that time, “remember: Hijrah is always an option and sometimes an obligation.” The family flew to London, then Cairo. Yahya and Tania lived in Egypt for the next two years, at first happily: The boys were clever and precocious—YouTube videos show the younger one reading words in English, French, and Arabic before the age of 3—and they were joined on Christmas Day 2011 by another boy. The family sailed feluccas on the Nile and savored life beyond the reach of the U.S. government. Yahya earned money by translating fatwas from the salaried religious scholars of the government of Qatar. Ever allergic to human authority, he seethed at the banality of the fatwas and the government clerics’ abject servitude to tyrants. None of the fatwas ever mentioned what he considered the core imperatives of Islam, stressed by Ibn Hazm a thousand years before, such as the establishment of a caliphate and emigration from lands of disbelief. The scholars relentlessly glorified the Qatari royal family. The fatwas, Yahya claimed, were based not on evidence but on mere opinion.
– What Yahya Abu Hassan has described as the "best day of his life" involved sneaking his emaciated, pregnant wife and three sick young kids through a barbed-wire fence over the Syrian border to Turkey, where he didn't even say goodbye before they were whisked to safety. That day in September 2013 was the day Hassan ditched his family to devote himself to helping ISIS set up a caliphate, his story told in a preview for a longer article by Graeme Wood appearing in the Atlantic's next issue. Wood details Hassan's reputation as one of the most revered "teachers" among jihadist circles, known for his "staggering mastery of Islamic law and classical Arabic language and literature," as well as his fluency in English. When Wood first heard about Hassan in 2014 while researching a previous Atlantic article about ISIS, he was curious about his origin story and started poking around. First he found links to Hassan and his extreme views, but further detective work involving nomenclature and Google searches led to an astonishing discovery: a DOJ release about the 2006 conviction of data technician John Georgelas, who used to live in Texas not far from Wood, and who Wood determined was Hassan. What Wood found out next about the Greek-American is fascinating. An in-person conversation Wood had with Georgelas' father, Tim, about John—who Tim describes as once an easily swayed "follower" who experimented with psychedelic drugs—is especially revealing, as is Wood's scrutiny of Georgelas' relationship with his ex-wife, once a fellow jihadist. Most chilling is Georgelas' current ISIS role, in which it's speculated he may now hold the second most-powerful position. "He knows how to speak to Americans, how to scare them, how to recruit them—how to make the Islamic State's war theirs," Wood writes. Read the deep dive at the Atlantic.