Jihadist strategy has always been dynamic and opportunistic. Militant groups, which are typically outgunned and outspent by their state opponents, have long sought to exploit both adversaries’ errors and also changes in the operating environment. Seismic strategic shifts by these groups have been common, not because they lack strategy, but rather because — like start-up firms in the economic sphere — their strategy relies on acting decisively in response to new opportunities. We are about to witness a major, and in many ways distinctive, shift in jihadist strategy spurred by the ongoing battlefield losses experienced by the Islamic State in Iraq and the Levant (ISIL). (Donald Trump’s election as the next U.S. president is likely to have further strategic impacts, but it is too early to analyze them comprehensively.)

The main challenge that confronts ISIL is sustaining itself as an organization even as its “state” becomes non-viable, and as its claims to being a universal caliphate appear increasingly outlandish. As Mosul comes under assault at the same time that U.S.-backed forces have launched an offensive to retake Raqqa, one obvious path for ISIL is leveraging its spectacularly successful terrorist attacks throughout the globe to try to sustain itself as a preeminent jihadist brand. But ISIL faces a dilemma: The group’s state made it so potent at planning and executing major terrorist attacks, and as its state declines, so too will its terrorist capabilities.

As it tries to find a way to thrive despite this problem, ISIL will no doubt return to the age-old jihadist debate about the relative merits of centralized and decentralized militant models. In doing so, one place ISIL will look is to the principles articulated by some of the movement’s most prominent strategists, including Abu Musab al-Suri. But ISIL is in a very different place than al-Qaeda was when the latter group had to adapt to the loss of its Afghanistan safe haven just after the 9/11 attacks. ISIL has operated across a larger contiguous geographic area than anything we have seen previously from jihadists, and has been able to take advantage of advanced encryption that did not exist in 2001. Thus, if it survives as an organization, ISIL will almost certainly forge its own unique twist on the question that proceeds from a position of strength relative to what Suri envisioned, and that anticipates a faster return to territoriality.

Leaderless Jihad vs. Leader-Led Jihad

Jihadists have long debated whether a centralized or decentralized organizational model is optimal. This debate extends also to terrorist attacks: Is it more effective when they are conceptualized and planned by a central organization, or are “lone wolf” attackers a greater threat?

ISIL employed and publicized both centralized and somewhat (though often not entirely) decentralized attacks abroad when it stood at its apex as a state. In addition to headline-grabbing attacks in places like Paris, Brussels, and Istanbul, the group has claimed responsibility for dozens of less sophisticated strikes — including, recently, a stabbing spree at a Minnesota shopping mall, another stabbing attack in Sydney, and a failed plot by several young Frenchwomen whom an ISIL planner “guided remotely” to attack Paris’s Notre Dame Cathedral. ISIL’s continuing decline will likely cause it to place greater emphasis on smaller scale strikes, which require less central direction and organizational backing.

A key architect of a more decentralized approach to terrorism and jihadist militancy is the aforementioned Abu Musab al-Suri, who wanted militants to engage in smaller but more frequent attacks against their enemies, and to launch these attacks not through a central organization but through numerous decentralized and disconnected cells. While it may be tempting to paint Suri’s approach as now being powerfully reasserted, a careful reading of his life and the evolution of jihadist strategy reveals a more complex picture. Jihadist groups rarely, if ever, wholesale re-embrace their strategists of yesteryear. Rather, these strategists’ principles might be re-examined, and applied in new ways to new circumstances. Such will be the case for ISIL’s read on the newly-relevant Suri, who articulated his principles against a strategic backdrop that no longer holds true.

Put simply, the world that prompted Suri to write his 1600-page magnum opus The Call for Global Islamic Resistance is a distant memory. At the time Suri wrote his treatise, the United States had recently dislodged the Taliban from Afghanistan in response to the 9/11 attacks. America stood tall as an unrivalled military, economic, cultural, and diplomatic superpower; the countries of the West, despite their internal squabbles and differences, remained a relatively cohesive bloc boasting shared interests and values. Jihadists’ enemies were so strong that trying to openly declare and sustain a jihadist state was unwise, perhaps even suicidal. Indeed, even organizational ties could be deadly, as intelligence services — with overwhelming surveillance capabilities that jihadists still didn’t fully comprehend — could quickly unravel militant networks, killing or capturing the members.

The past couple of years dramatically illustrate how much the world has changed. ISIL’s dying caliphate aside, the United States and its allies stood by helplessly as dictators aligned with the West fell in Tunisia and Egypt. The United States and its NATO allies intervened to topple Muammar Qaddafi, who had been a bulwark against Islamist gains in Libya. Jihadist insurgencies are gaining steam in Mali and Somalia. And al-Qaeda continues to control significant territory in coastal Yemen. The pace of jihadist attacks in Europe is unprecedented, and a confluence of factors have allowed jihadist networks in Europe to emerge that are broader and more deeply interconnected than analysts would have thought possible even five years ago (that is, prior to the boom in end-to-end encryption, such networks would surely have been detected and disrupted). The United States and its allies are simply no longer in a position to crush jihadist forces wherever and whenever they assemble.

As the world changes, so too does jihadist strategy. So as ISIL tries to transition from jihadist state to insurgency or transnational terrorist group and eventually back into a state, a new strategic doctrine will likely be born. An examination of Suri, his ideas, and their application illuminates the likely emergence of this new jihadist doctrine.

Suri’s Journey

Suri is closely tied to ISIL’s bitter adversary, al-Qaeda — with whom he had a falling out due to strategic disagreements, but eventually reconciled with and had rejoined by 2004. Born Mustafa Setmariam Nasar, Suri is a Syrian with Spanish citizenship, and one of al-Qaeda’s most prolific authors on insurgent and terrorist strategy and tactics. Suri’s writings significantly influenced other high-profile jihadist leaders, including ISIL’s father figure Abu Musab al-Zarqawi. Suri’s current whereabouts are unknown.

When al-Qaeda carried out the 9/11 attacks, Suri condemned them. He argued that by striking the United States, Osama bin Laden had invited the American response that removed the Taliban from power. Suri explained that jihadists were incapable of winning prolonged battles against conventional forces from Western militaries, or even the Arab world’s professionalized forces. His ideas about jihadists’ inherent military weakness were shaped by his experience in 1982 in Hama, Syria. There, Hafez al-Assad — father of current Syrian president Bashar al-Assad — and the Syrian military crushed a Muslim Brotherhood-led uprising with brutal efficiency.

As Thomas Friedman documented in his classic book From Beirut to Jerusalem, the devastation at Hama was overwhelming, with “whole neighborhoods of crushed apartment buildings bearing silent witness to the remarkable events that transpired.” The number of those killed in the Syrian onslaught is unknown, but Friedman notes that estimates range from 10,000 to 25,000 dead — mainly civilians — with thousands more displaced. The brutality with which the Syrian military crushed the Hama uprising was meant as a stark warning to others who might defy the regime.

Despite this bleak demonstration of the massive advantages that jihadists’ foes enjoyed, the 1980s were actually a heady time for Islamist militants. Islamists’ biggest military accomplishment of the decade, of course, was when Afghan mujahedin, with an over-mythologized assist from the “Afghan Arab” foreign fighters, expelled the occupying Soviet army from their country following a bloody decade-long fight. Suri didn’t think, though, that this meant Islamist fighters could regularly go toe-to-toe with their foes. He wrote that the Afghan mujahedin were only able to repel the Soviet occupation with the help of substantial funding and materiel from the United States, Saudi Arabia and Pakistan. Suri knew, following the 9/11 attacks, that no such aid would be forthcoming from any of the world’s powerful nation-states.

Thus, The Call for Global Islamic Resistance urged that individual terrorist acts carried out by small cells replace al-Qaeda’s old structure. He argued that the centralized, hierarchical model of jihadism could not overcome the U.S.’s technologically advanced military, and that regional security cooperation and intelligence sharing made a hierarchical structure dangerous. Suri suggested that, in contrast, decentralization would immunize terrorist cells from detection through the capture and interrogation of members of other cells. Suri believed that a looser, decentralized network would present more problems for the West, resulting in “thousands, even hundreds of thousands of Muslims participating in jihad.”

Though Suri’s strategic writings did a great deal to shape al-Qaeda’s approach during its post-9/11 nadir, eventually Suri’s influence within al-Qaeda was eclipsed by another strategist who also provided an influential blueprint for ISIL. As al-Qaeda gained new operating space in Pakistan and elsewhere, it looked to the work of Abu Bakr Naji, whose book The Management of Savagery argued that once jihadists hold territory, they should erect a governing apparatus to enforce Islamic law and provide security, food, and medical care. Naji believed that a high command should oversee these efforts.

The preference of al-Qaeda’s leadership for Naji’s approach over Suri’s reflects a long-standing inclination for centralization, along with two other factors. First, shifting events made a robust role for central leadership increasingly viable, as al-Qaeda’s safe haven in Pakistan allowed the leadership’s reassertion. Also, far from Suri’s vision of thousands or hundreds of thousands answering his call, al-Qaeda never received an overwhelming reaction when it urged Muslims to carry out lone-wolf attacks.

Later, an al-Qaeda cleric whom Suri influenced would fuse the leaderless and leader-led jihad models. Anwar al-Awlaki, the al-Qaeda in the Arabian Peninsula (AQAP) official and propagandist whose YouTube sermons frequently cite Suri’s teachings, called for individual attacks even as AQAP organized centrally-directed terrorist plots. Awlaki seemingly received a greater response to his calls for lone wolf attacks than any other al-Qaeda leader. According to the Counter Extremism Project, Awlaki has influenced as many as 88 known extremists in the United States and Europe.

An era of jihadist centralization — albeit with continuing calls for lone-wolf attacks and support for loosely-connected cells — followed Awlaki’s death in 2011, driven both by ISIL’s establishment of a jihadist state that was unrivaled in geographic breadth and also al-Qaeda’s quiet but no less real control of territory. But now ISIL will be forced to adapt its tactics and operations in response to its mounting losses.

While Suri will reemerge as a thinker of some significance for ISIL, ultimately the course ISIL charts will reject some of his core assumptions. The group is likely to find a new approach that relies on some of Suri’s ideas but does not adopt them wholesale.

Leaderless ISIL?

In 2014, the late ISIL spokesman and nominal external operations chief Abu Muhammad al-Adnani provided somewhat of a CliffsNotes version of Suri’s work when he admonished Muslims who were prevented from joining the jihad in Iraq and Syria to target Westerners in their home countries. “Smash his head with a rock,” Adnani implored, “or slaughter him with a knife, or run him over with your car.”

Adnani’s call to arms — and the calls of ISIL’s broader, once-potent social media machine — did not fall on deaf ears. In addition to a seemingly endless stream of ISIL-connected attacks in Europe, over 100 individuals have been charged in the United States with ISIL-related offenses since March 2014. Nearly one-third of those arrested stand accused of involvement in plots to carry out attacks on U.S. soil.

Many ISIL attacks were centrally directed through its external operations apparatus, known as the amniyat al-kharji. While the amniyat is likely to decline significantly due to attrition within the group’s caliphate, ISIL may not really go away even in places where it is ousted as a governing force. As Patrick Ryan and Patrick B. Johnston recently noted in War on the Rocks, ISIL has “gone underground” in response to previous clearance operations, and in places like Mosul it is likely to adopt the approach of “deactivating and dispersing its military units and reinforcing its intelligence, security, administrative, and financial groups.” One potential obstacle it faces in making this adaptation is that, in contrast to Maoist-style insurgencies that try to win over the population, ISIL has instead taken on a Focoist model of revolutionary warfare, and has alienated many of the people upon whom a transition to insurgency would rely.

Regardless of its success in building an insurgency, ISIL has achieved a level of mass mobilization internationally that al-Qaeda never did. This makes the strategic use of truly disconnected cells more feasible than it has ever been for jihadists. Much like Awlaki before them, ISIL is unlikely to view its options as a binary, and will probably employ leader-led and leaderless attacks in tandem as complementary elements of a broader strategy. Further, ISIL knows — because it showed the world this fact — that jihadists can capture significant territory and hold off the world’s most powerful militaries for years. This was a particularly impressive feat for ISIL because the group’s flawed strategy caused it to fight a multi-front war almost from the outset. Thus, ISIL’s goals will likely be more expansive, and more immediately so, than those advocated by Suri.

ISIL may similarly fuse this hybrid model with other strategic objectives. One defining feature of the group’s military strategy has been that it doesn’t want to have the time and place of violence dictated to it. Pressure against ISIL in Mosul may yield a counterattack in Kirkuk. It is possible that, consistent with this doctrine, losing in Iraq and Syria will prompt ISIL to channel more resources into attacking Lebanon, Turkey, Jordan, the Gulf or Europe. But merely having the will to attack is not the same as the means: ISIL has created sky-high expectations about its capabilities, and it may experience a drier period than it has known to date, where it can no longer carry out attacks throughout the globe at will.

One X factor in all of this is the boom in end-to-end encryption. It used to be that poor ability to communicate was a factor in relative decentralization. But the obstacles to secure communication are declining globally. This is a big difference from 2001, and a big difference even to the obstacles that ISIL’s predecessor faced in 2007-2009.

All of these threads provide an indication of the strategic doctrine that ISIL is in the midst of forging. “What’s past is prologue,” Shakespeare famously wrote. A close examination of the strategists of yesteryear provides a prescient guide for what is to come, but does not tell the entirety of the tale. Reading Suri’s works can help us to anticipate ISIL’s next moves, but a full understanding of the strategist’s life reveals that we need to look beyond his words alone. Much of ISIL’s adaptations will be wedded to the broader changes in the environment in which ISIL will be attempting its rebound.

Colin P. Clarke is a political scientist at the RAND Corporation, where his research focuses on terrorism, insurgency and the future of political violence. Daveed Gartenstein-Ross is a senior fellow at the Foundation for Defense of Democracies and the chief executive officer of Valens Global.

Correction: A line about Suri being released from prison was deleted as claims about his release are not substantiated.