The new book by the investigative journalists Adrian Levy and Catherine Scott-Clark, The Exile: The Flight of Osama bin Laden, charts the career of al-Qaeda’s founder, Osama bin Laden, up to the day he became a household name—11 September 2001—through his downfall in 2011, to the end of 2016, when al-Qaeda was more powerful than ever. It is a thoroughly absorbing account, bringing to light vast tranches of new facts, including many intricate details of how al-Qaeda operated on a human, day-to-day level, and of those states and para-states that shielded the terror network, collaborated with it, and enabled it—and still do.

The gathering of the Bin Laden network in Sudan and then in the Taliban-held areas of Afghanistan in the 1990s is a familiar story, but the splits and debates among the Arab jihadists around Bin Laden, including the opposition of significant numbers of them to the 9/11 massacre, is perhaps less well known. The authors trace out how Bin Laden manipulated his own quasi-institutions to get his way. First, Bin Laden took on the plan of a man, Khalid Shaykh Muhammad (KSM), who was not even a member of al-Qaeda, and then, ahead of the crucial vote, packed the shura (consultation) council with ultra-zealous Egyptians by engineering a merger between al-Qaeda and Islamic Jihad, led by Ayman al-Zawahiri.

This high-stakes intrigue couples with the less elevated problems of running a clandestine terrorist organization. Bin Laden’s then-security chief, Nasser al-Bahri (Abu Jandal), was sent back to his native Yemen shortly before 9/11. Al-Bahri had arranged for Bin Laden to take another wife, Amal, as part of a plan to reinforce relations with an influential Yemeni tribe—Yemen at the time serving as an important recruitment and fundraising arena, as well as a potential fallback base if ties continued to deteriorate with the Taliban. Amal was a child; her presence infuriated Bin Laden’s other wives, who refused to speak to the girl, and set about al-Bahri’s wife, Tayez. Surely she must have known what her husband was going to do for Bin Laden? Why had she not told them? Amal had little choice but to accept her ostracism; Tayez was not so trapped. “[E]mbarrassed by the cattiness of his family,” the authors explain, Bin Laden “gave his security chief permission to relocate to Sana’a, dressing it up as a ‘mission’ […] to shore up support among Yemeni tribal leaders, sheikhs, and imams in preparation for al-Qaeda’s relocation there.”

When an enraged United States swept the Taliban from power in late 2001, and had “the Shaykh” and his troops cornered at Tora Bora, they ran smack into the contradiction that would bedevil the Afghan campaign ever-afterwards: not only were proxies of the “S-wing” of Pakistan’s Inter-Services Intelligence (ISI), like Jaysh-e-Muhammad and Lashkar-e-Tayyiba—terrorist instruments built to wage a shadow war with India—actively helping al-Qaeda operatives cross into Pakistan and protecting them once they were in the country, but powerful elements of the ISI in toto and the Pakistani military-intelligence establishment more broadly supported a policy of ensuring America could not succeed in eliminating al-Qaeda. At its most cynical, this policy was about keeping the cheques coming; for quite a number it was a deeply sincere commitment to the jihadi cause.

The role of Hamid Gul, the head of ISI during the closing stages of the Soviet occupation of Afghanistan, as the lynchpin of Pakistan’s underworld of “deniable” state-sponsored terrorism was reasonably well-understood. The scenes sketched by Levy and Scott-Clark of the behavior of on-duty military and intelligence officials in Pakistan constitute some of the most shocking passages in the book.

Lt. Gen. Mahmud Ahmed, one of the conspirators who overthrew the civilian government in Pakistan in 1999, bringing Pervez Musharraf to power, was head of ISI during the crucial period. In the U.S. on 9/11, and trapped there for several days afterward, Ahmed was assailed by the CIA station chief as soon as he got back to Pakistan. As soon as he was free, Ahmed visited with Taliban leader Muhammad Umar. “Never hand over Shaykh Osama,” Ahmed told Mullah Umar, and protect him “at any cost.” Ahmed then began sharing intelligence with Umar, provided training in guerrilla warfare and resisting American air power, sent in a team of ISI specialists to help the Taliban booby trap the cities, and sent “so many Pakistani fuel tankers and supply trucks toward the Taliban that they choked the border crossing into Afghanistan at Chaman.” In December 2001, after Islamabad reached an accord with the U.S. to crush al-Qaeda in a pincer movement in the mountains along the Durand Line, one of ISI’s assets tried to blow up the Indian parliament, the Lok Sabha, nearly triggering a thermonuclear war on the Subcontinent—and dragging away the troops that had been about to put paid to al-Qaeda.

Bin Laden and a small cadre, protected by Ibrahim Saeed Ahmed, the fixer-courier made famous by Zero Dark Thirty as Abu Ahmad al-Kuwaiti, headed into the Pakistani tribal zones, which even ISI had a hard time mastering. After several years of living in increasingly-crowded homes, Bin Laden settled in the Abbottabad compound in late August 2005. Shortly thereafter, ISI would, through a cut-out, Fazlur Rahman Khalil, the godfather of the Taliban, reach out directly to Bin Laden, offering to ease his stay in Pakistan: he would keep quiet and pretend to be dead; they would ensure that their networks in the police and the military kept the Americans and anybody else away from him and his senior lieutenants. As late as August 2010, ISI was running lines of communication to Bin Laden, looking for a non-aggression pact. Bin Laden suspected a ruse to lure him out; we may never know.

That same month in the summer of 2010, Bin Laden left the Abbottabad compound. This was not the first time. Among other trips, Bin Laden had attended the planning meeting in Mansehra, fifteen miles north of Abbottabad, for the extraordinary atrocity in Mumbai in November 2008—a crime “facilitated by Lashkar, overseen by the ISI’s S-Wing, and sponsored by Al Qaeda.” This time Bin Laden was arranging communications with his wife, Khairiah, who was in Pakistan, though for security reasons at a distance. She had just been released from Iran with Bin Laden’s son, Hamza, and some other family members.

In escaping from the “White Mountain” at the end of 2001, Osama had called on an old friend: Gulbuddin Hekmatyar, a Mujahideen warlord, who was at least as notorious for reducing Kabul to ruins in the civil war with the other Mujahideen commanders that followed the expulsion of the Soviets from Afghanistan as he was for his part in the great struggle with the Red Army. By 2001, Hekmatyar was based in Iran and being run by General Qassem Soleimani, the commander of the expeditionary Quds Force within the Islamic Revolutionary Guard Corps (IRGC). “Steered from Tehran, Hekmatyar’s network in Afghanistan remained active, and it responded to Osama’s cry for help,” the authors note. As Bin Laden and his party headed into Pakistan, much of al-Qaeda’s military and religious leadership went the other way into Iran. This was no accidental development.

In January 2002, Soleimani directly approved the provision of safe haven to al-Qaeda. By March 2002, the trickle of al-Qaeda operatives into Iran became a torrent when Soleimani’s men were ordered to set up camps on the border to house al-Qaeda terrorists and their families. Some groups of jihadists were moved to Tehran, put up at the Amir Hotel, with their wives and children kept across the road at the four-star Howeyzeh Hotel—both just down the street from Soleimani’s headquarters in the former U.S. embassy. False documents were then given to these men to allow them to move to southeast Asia and beyond. A number of al-Qaeda’s more senior leaders—the military men, Sayf al-Adel and Abu Muhammad al-Masri; the strategist Mustafa Setmariam Nasar (Abu Musab al-Suri); IS’s founder, Ahmad al-Khalayleh (Abu Musab al-Zarqawi)—plus Bin Laden’s family had settled into networks among Arab populations in Iran. Through Mahfouz Ould al-Walid (Abu Hafs al-Mauritani), Bin Laden’s chief cleric in Afghanistan, they came out of the shadows and settled on terms with the Quds Force.

These terms sometimes resembled house arrest, though even in so-called captivity al-Qaeda was allowed to run its operations. Sayf al-Adel directed the bombing of Riyadh from Iran in May 2003, and al-Adel, who was particularly close to Soleimani, was made fully aware that where his terrorism overlapped with Iranian interest, the Quds Force would help him. Al-Qaeda’s foreign director, Abu al-Khayr, was free to work on a “dirty bomb,” despite being in custody. (Abu al-Khayr was allowed to leave Iran in 2015, moving straight to Syria—where Iran is supposedly holding the line against al-Qaeda terrorists. Abu al-Khayr was al-Qaeda’s overall deputy when the American-led coalition struck him down in February 2017.)

At other times, particularly after 2007, al-Qaeda was much freer. To be sure, there was a constant struggle for leverage—a hostage trade had sprung Khairiah and the others in 2010—but when it came down to it, Iran would not, despite repeated requests, surrender al-Qaeda to the United States, and to this day allows al-Qaeda to run its “core pipeline” from Pakistan, through Iran, into the Arab world. When anything like deportations occurred, such as of al-Zarqawi, who spent a brief moment in an Iranian prison, Iran assisted al-Qaeda operatives to make trips they were going to make anyway—and al-Zarqawi was sent on his way with a satellite telephone, passports, weapons, and money from the Quds Force to help him orchestrate his mayhem in Iraq.

The legwork and sourcing in the book are incredible. When one reaches the moment, in May 2011, that the Navy SEALs come for Bin Laden, and the man finds his compound is a trap from which there is no escape, the authors are able to narrate events in a wholly unique way. As the helicopters closed in, “Osama awoke, a fearful look on his face,” they write. We are told what his wife, Amal, “thought” events sounded like. For a moment one wonders how this can possibly be known, and then one checks the footnotes. Levy and Scott-Clark have asked the only people who could know.

Any criticisms are matters of emphasis and interpretation.

In my view, the book too easily dismisses the question of Saddam Hussein’s connections to al-Qaeda in favor of the conventional wisdom that there were no such connections. One example: when discussing the movement of a dozen al-Qaeda-linked jihadists to Baghdad in May 2002, including al-Zarqawi, the authors write that the Bush administration—at the insistence of Secretary of State Colin Powell—had blocked a plan to kill al-Zarqawi at his base in northern Iraq, in order to use him to justify the coming invasion, “enabling Zarqawi to slip down into Baghdad.” Even on its own terms, this narrative hides the agency of those involved: high-profile wanted men did not just “slip” into Saddam’s capital. But the narrative does not hold up once it is factored in that Powell and his deputy, Richard Armitage, were more hardline even than CIA Director George Tenet in their opposition to the Iraq invasion.

Mahfouz al-Walid looms large as a source in the book, and just occasionally there is a sense that some of his self-justifications and factional leanings are coloring events. “We here in Afghanistan […] could not contain our joy when we saw America taste, for one day, what the Islamic people have been swallowing every day—for decades,” al-Walid told an Al-Jazeera interviewer in November 2001. “One of the acts of grace of this generation is to kill Americans.” Al-Walid was only the second al-Qaeda leader to appear in public after 9/11. He now says this was an ad hoc statement made in anger after he had seen the bloody aftermath of an American airstrike. It’s just a little too convenient.

Finally, the framing of the struggle within Iran about hosting al-Qaeda’s leadership as one between reformists and hardliners rather pulls apart on itself. Whether or not one accepts the findings of the CIA, to the effect that these intra-elite schisms are sideshows in a state run with a firm hand by Supreme Leader Ali Khamenei and his Quds Force, Iran did harbor al-Qaeda’s core leadership. The people who matter in Iran sheltered al-Qaeda in a moment of existential peril, left them free to orchestrate terrorism beyond Iran’s borders, and continue to keep operational leaders of al-Qaeda, like Sayf al-Adel and Abu Muhammad al-Masri, safely out of range of American drones. This is an important conclusion to factor in moving forward.