On its lightning-fast advance through Iraq, the radical jihadi group the Islamic State of Iraq and al-Sham (ISIS) has captured Mosul, Iraq’s second-largest city; Tikrit, Saddam Hussain’s birth city; and many other towns along the way. Now, with help from former Baathists and Sunni tribal forces, the group is making its way toward Baghdad. ISIS’ astonishing success could be a harbinger of a tectonic shift within the jihadi movement. Namely, ISIS could supplant al Qaeda as the movement’s leader.

This showdown has been several years in the making. The friction between the two groups goes back years. But the relationship did not reach a breaking point until April 2013, when Abu Bakr al-Baghdadi, the leader of ISIS, expanded his group into Syria and attempted to subordinate the local al Qaeda branch, Jabhat al-Nusra (JN), to his own authority. JN rejected Baghdadi’s leadership, and Ayman al-Zawahiri, al Qaeda’s chief, tried to calm the dispute by announcing that JN would remain responsible for jihad in the Syrian arena and ISIS would keep to Iraq. ISIS refused to accept Zawahiri’s decision and continued its expansion into Syria. Along the way, it trampled other Syrian rebel groups, including radical Islamists. Soon, ISIS’ overreach provoked a backlash, and opposing rebel groups mounted a counteroffensive. For its part, JN eventually sided with the anti-ISIS forces. By February 2014, the rift between ISIS and the Syrian opposition had led Zawahiri to disown the group.

The differences between ISIS, on the one side, and al Qaeda and JN, on the other, are not merely about power and control of the jihadi movement. As important as these aspects are, the groups have serious differences when it comes to strategy, tactics, and Islamic authority. They differ on issues such as the implementation of harsh Islamist laws, the killing of Shia civilians, and the right of one group to impose its authority over all others. The groups don’t disagree about the legitimacy of all of these things, but al Qaeda is more patient and ISIS is generally more radical and uncompromising. For that reason, its traipse through Iraq represents a serious organizational, strategic, and ideological blow to al Qaeda.

ISIS’ display of power will likely strengthen its hand over al Qaeda in Syria and beyond. First, the military successes brought the group substantial spoils: ISIS looted bank deposits worth close to $500 million, captured large quantities of military equipment, and liberated hundreds of fighters from prisons in territory now under its control. All of that will prove very useful in Iraq and in Syria. As money and manpower breed success, success will breed more success. ISIS’ popularity will likely rise among radicals, and that will translate into more funding and volunteers for the group. ISIS could rapidly mobilize those forces along the vanishing border between Iraq and Syria, which it now increasingly controls, and launch even more ambitious campaigns while it fends off attacks in Syria.

Second, beyond raising ISIS’ profile, the terrorist group’s march through Iraq also diminishes al Qaeda’s. Al Qaeda’s greatest achievement was the 9/11 attacks, but that was 13 years ago. Many of today’s jihadis were young children at that time. Moreover, the attack on the United States was only supposed to be a means to an end: the establishment of an Islamic caliphate in the heart of the Middle East. Al Qaeda franchises did manage to gain (and then lose) some territory in Yemen, Somalia, and northern Mali. But these territories are smaller in size and significance than what al Qaeda wanted -- and what ISIS controls today. Although al Qaeda may have started the march toward the reestablishment of the Caliphate, it is ISIS that seems to be realizing it.

Third, success breeds legitimacy. For the past year, al Qaeda’s main tactic against ISIS has been to try to delegitimize the movement. And, until now, al Qaeda’s strategy had been moderately successful. Popular jihadi scholars, such as Abu Muhammad al-Maqdisi and Abu Qatada al-Filistini, released messages of support for al Qaeda and strongly denounced ISIS -- which turned some would-be adherents away from the upstart. ISIS was able to muddle through the delegitimization campaign by hanging on to the support of some young and popular jihadi scholars. And, even before the surprise in Iraq, the trend in the jihadi movement had been toward the decentralization of religious authority; social media offers a platform for nearly any charismatic jihadi to gain a following. At the same time, moreover, young jihadis have increasingly come to view the old guard -- often identified with al Qaeda -- as disconnected from reality. They give more respect to warriors than to religious scholars. All that plays to ISIS’ favor, especially now that it has real victories under its belt. It can use those as evidence that it has been right all along and that its ways are truthful. Zawahiri’s criticisms, delivered from his hiding place in Pakistan, are weak in comparison.

Fourth, symbolism works to ISIS’ advantage. In the past, al Qaeda, Syrian rebel groups, and numerous jihadi scholars criticized Baghdadi’s claim that ISIS represents a genuine Islamic Emirate -- with rights that surpass any privileges a jihadi organization may claim -- by arguing that control over territory is essential for the creation of Islamic Emirate. Now, ISIS holds territory larger than many countries. Similarly, although Baghdadi has been criticized for using the title Emir of the Believers, which is reserved for the Caliph, his organization’s recent accomplishments make the title seem more appropriate. Further, it is lost on few radical Islamists that Baghdadi’s forces -- merely 5,000 men -- defeated 90,000 soldiers on a march toward Baghdad, the seat of the Abbasid Caliphate for 500 years.

War is, of course, unpredictable, and ISIS’ good omens could evaporate if it doesn’t hold on to its gains. Unfortunately for al Qaeda (and Iraqis and Syrians), that seems unlikely to happen. ISIS’ march is the result of a well-thought-out plan that was a long time in the making. The crumbling Iraqi military is ill equipped to quickly reverse ISIS’ progress, and the United States appears unwilling to step in, at least in a dramatic way.

Al Qaeda knows that. And so, despite the animosity between the two groups, it seems to be bound to congratulate its rival for its victories. It might offer advice, but it can’t go against ISIS. It will be expected to offer support or at the least cheer for its rival, not stick a knife in its back. To al Qaeda’s further disadvantage, disagreements over methods and authority are increasingly less salient. Al Qaeda’s appeal relative to ISIS’ is greater when questions of how to run a territory populated by Sunni Muslims who do not subscribe to the Salafi-jihadi radical interpretation of Islam take center stage. When the front stabilizes and the intensity of the fight subsides, such questions will return and the inherent weakness of ISIS will resurface. ISIS is an extremely capable force, but its battle achievements do not make it any more appealing as a government. To succeed in the competition with ISIS, al Qaeda could try to outdo it in some way -- through advances against the Assad regime, quality operations in the Arabian Peninsula and in North Africa, and attacks in the West. Still, given the weakening of al Qaeda’s central command, the limitations of its franchises, and this most recent blow to its reputation, its ability to recover is far from certain.

You are reading a free article.

Subscribe to Foreign Affairs to get unlimited access.

  • Paywall-free reading of new articles and a century of archives
  • Unlock access to iOS/Android apps to save editions for offline reading
  • Six issues a year in print, online, and audio editions
Subscribe Now
  • BARAK MENDELSOHN is an Associate Professor of political science at Haverford College and a Senior Fellow at the Foreign Policy Research Institute (FPRI). Follow him on Twitter @BarakMendelsohn.
  • More By Barak Mendelsohn