The barbaric shooting in the Pulse nightclub in Orlando that resulted in the death of 49 people and the injury of 53 others is the latest in a string of terrorist attacks in the West. It is too early to determine whether the perpetrator, Omar Mateen, was directed or only inspired by ISIS. But the attack, which comes on the heels of the strikes in Paris and Brussels and in the wake of the group’s repeated calls for lone wolf attacks, reflects ISIS’ growing interest in expanding the battlefield to the West. A central question arising is whether these attacks also signal a transition for the self-styled caliphate to the global jihadi ideology of al Qaeda. If yes, the implication is clear: If ISIS has indeed become more like al Qaeda, then the two groups might someday cooperate and, consequently, the threat to the United States will grow. The preeminent terrorism scholar Bruce Hoffman recently proposed, notwithstanding the current hostility between ISIS and al Qaeda, that unification between the two groups is eventually possible.

To be sure, Hoffman is cautious; he focuses on the groups’ relations in five years’ time rather than in the near future. He also allows for cooperation short of unification, which would take the form of an alliance or tactical cooperation. In fact, the danger of the two groups’ joining forces in 2021 is perhaps the least of the West’s worries. Until recently, scholars and pundits focused on the danger that al Qaeda would be absorbed into the more successful ISIS. But that group’s string of defeats in Palmyra, Ramadi, Sinjar, and elsewhere flips the equation. Such losses could alter the dynamics within the jihadi movement with considerable ramifications for the wars in Syria and Iraq and for the fight against terrorism in the West.

On the face of it, Hoffman’s claim is not unreasonable. After all, al Qaeda and ISIS share striking similarities: both emerge from the Salafist strand of Islam, seek to restore the caliphate, and employ indiscriminate violence against Westerners. In a previous incarnation, ISIS was even a branch of al Qaeda. Nevertheless, the likelihood of the two uniting forces remains low.

The significant differences between the two groups extend beyond the wide disparity in each one’s power. ISIS functions as a state, controlling a vast territory with millions of residents, whereas al Qaeda operates primarily as an organization with considerably fewer resources. To the extent that al Qaeda’s branches have territorial possessions, they are significantly smaller and of less strategic importance than are ISIS-controlled territories. And although ISIS has prioritized the reintroduction of the caliphate, al Qaeda views this as a step to be postponed until conditions can guarantee its survival.

Al Qaeda-linked Nusra Front fighters carry their weapons on the back of a pick-up truck during the release of Lebanese soldiers and policemen in Arsal, eastern Bekaa Valley, Lebanon, December 1, 2015. Reuters In addition, after the backlash that followed the 2008 collapse of its Iraqi branch—the very branch that resurged to become ISIS—al Qaeda has sought to present a softer face. Al Qaeda learned from the Arab Spring, too. Osama bin Laden and his successor Ayman al-Zawahiri believed that the group would need to capture the hearts and minds of the region’s Muslims to succeed. In line with its increased focus on Muslim populations, al Qaeda has denounced ISIS’s proclamation of the caliphate as not merely premature, but also illegitimate because its process denied Muslims their right to choose the caliph and intensifies divisions instead of promoting unity.

According to Syria expert Charles Lister, al Qaeda still does wish to establish an Emirate—a more modest form of Islamic entity than a caliphate—in northern Syria, but whether al Qaeda will pursue one largely depends on the ability of its Syrian branch Jabhat al-Nusra to gain the support of other prominent Islamist groups, primarily Ahrar al-Sham. In fact, al Qaeda has relied increasingly on cooperating with other Islamist groups and on sharing authority in the locations it captured.

ISIS, by contrast, rejects sharing power. It insists that other jihadist groups accept its authority, especially in Iraq and Syria. In some locations, such as Nigeria and Egypt, the groups that join the state maintain some autonomy. Indeed, Boko Haram and Ansar Bait al-Maqdis were accepted wholesale as armies of the caliphate that receive directives and resources from ISIS yet retain their own organizational structures. In most cases, though, the best that other Islamists can hope for is to operate as individuals absorbed into ISIS forces. The mere act of declaring Abu Bakr al-Baghdadi a caliph was intended, among other things, to justify forcing other jihadi groups to accept ISIS’s authority and to present any criticism as rebellion against an allegedly legitimate caliph, which carries severe punishments.

Al Qaeda’s ability to withstand the rise of the Islamic State suggests that it will not succumb now, especially since ISIS is suffering military defeats and rapidly losing control of territory.

Meaningful cooperation between ISIS and al Qaeda would require ISIS to back down from its demands for obedience from local groups and from its harsh rhetoric about other Islamist groups, a highly unlikely shift. Alternatively, cooperation could result from a change in al Qaeda’s attitude toward its former branch and acceptance of its authority. With so much bad blood between the two groups, the odds of that occurring seem small.

Still, although ISIS and al Qaeda are pursuing dissimilar strategies, the involvement of Western, Russian, and Iranian forces in the wars in Iraq and Syria makes it possible for the two to bridge their differences. After all, mounting pressure from external forces further aligns the groups’ threat perceptions and deepens their shared interests. In their view, the presence of foreign forces validates their claims that there is a war on Sunni Islam, that the Sunni states do not care about their Sunni brethren in Syria and Iraq, and that most of the rebel groups these countries support cannot be trusted.

Much more difficult to overcome will be ISIS’s thirst for power along with ego fights between the leaders of two groups, the groups’ diverging organizational interests, and their incompatible approaches to the treatment of Muslims. Even as it is experiencing immense pressure on multiple fronts, ISIS still prefers to call on its supporters around the world to carryout lone wolf attacks to seeking accommodations with other jihadi groups. Despite its preoccupation with control, ISIS welcomes attacks by individuals it cannot direct and does not know but refuses to make any concessions to other groups that would erode its claims of authority.

A member of al Qaeda's Nusra Front climbs a pole where a Nusra flag was raised at a central square in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. Khalil Ashawi / Reuters Unwilling to accept its former superiors in al Qaeda as equals, ISIS has turned to subversion tactics. Trying to undermine al Qaeda from within, ISIS has put pressure on the group’s old affiliates to shift their allegiance. Remarkably, al Qaeda has been able to withstand the onslaught so far, with all its branches reaffirming their loyalty to al-Zawahiri. ISIS fares better with al Qaeda’s foot soldiers who are more susceptible to ISIS’s propaganda. All of the group’s branches have faced calls from the rank and file to join the caliphate. Small segments, including a few high-ranking figures, even defected to ISIS. Yet al Qaeda perseveres; smaller groups are pledging their allegiance to Jabhat al-Nusra, al Qaeda in the Indian Subcontinent trains hundreds of new volunteers in Afghanistan, and al Qaeda in the Islamic Maghreb is expanding its attacks to new locations in West Africa.

Al Qaeda’s ability to withstand the rise of the Islamic State suggests that it will not succumb now, especially since ISIS is suffering military defeats and rapidly losing control of territory. At the same time, members of both groups, especially outside the Middle East where personal connections often play a more meaningful role than do organizational affiliations, may cooperate. Moreover, although ISIS’s reversal of fortune will likely diminish its appeal and mitigate the pressure on al Qaeda, it could also bring al Qaeda’s foot soldiers to call on their leaders to assist in reducing the pressure on the ISIS.

The changing relationship between ISIS and al Qaeda has important implications for American planners. Although the United States must aggressively tackle the threat from both groups, it needs to consider the real risk that some of its actions would inadvertently bring unity to the jihadi camp. The assassination of al-Baghdadi or al-Zawahiri is one way the United States might shake up the relations between ISIS and al Qaeda. Continued bombing of Jabhat al-Nusra while forcing other Sunni rebel groups in Syria to accept a peace deal that would leave Assad in office is another. Although the two are unlikely to cooperate at this stage, the jihadi arena changes quickly. And, at the very least, the interconnectedness of the threats posed by the two groups means that the United States should adopt a more holistic assessment of the threats they pose. In short, the United States and its allies would be wise to pay greater attention to the relations between ISIS and al Qaeda, considering how actions against one threat affect the danger posed by the other and by the broader jihadi movement.