The civil wars in Syria and Iraq have transformed the jihadist threat to the United States. For the first time, a jihadist group, the Islamic State of Iraq and al-Sham (ISIS), has been able to combine an ambitious transnational agenda with control of substantial territory, resources, and urban population centers. A U.S.-led coalition has made some significant gains against ISIS in Iraq and, with luck and sound planning, it may continue to do so. The results in Syria, however, are meager, and the outlook deeply unpromising. This is mainly because, unlike in Iraq, where it has partnered with government and loyalist militia forces, the United States has no local partners that can decisively defeat ISIS in Syria. Lasting success requires aligning U.S. strategy with local Sunni Arabs’ priorities, by becoming more involved in resolving Syria’s civil war.

The United States leads a multinational coalition whose mission is to “degrade and destroy” ISIS. That coalition has relied largely on U.S. airstrikes against ISIS targets in Syria and Iraq, including fighters, ammunition depots, vehicles, barracks, and training grounds. The United States has also given material, training, and close air support to government forces in Iraq and Kurdish forces led by the People’s Protection Units (known by the Kurdish acronym YPG) in Syria. As a result, Iraqi government forces have retaken ISIS strongholds, including Tikrit, Baiji, and Ramadi, while the YPG has captured ISIS-held border areas and put pressure on the group’s supply lines. ISIS has lost thousands of fighters and morale has likely suffered, as have revenues from transporting and selling oil.

This is the full extent of gains against ISIS thus far. They are not insignificant. But in Syria in particular, the jihadists will almost certainly survive these pressures. Even if ISIS is severely weakened there, it is unclear who would replace it and address the conditions from which it emerged: the deep alienation of Sunni Arabs from the Syrian regime, unrelenting state violence, and the insurgency’s inability to defeat the government or protect the local population from the regime and ISIS alike. The next U.S. President will inherit some substantial tactical gains against ISIS, but those gains will probably be eclipsed by major shortcomings in the United States’s anti-ISIS strategy in Syria.

This is problematic: ISIS in Syria and Iraq is one and the same organization. ISIS entered Syria from Iraq and made that border irrelevant. Following that, ISIS in turn used Syria as a launching pad for its takeover of much of western Iraq. In short, ISIS can only be said to be defeated if it is beaten in both Syria and Iraq. Otherwise, it will use whichever presence it retains to project power into adjacent territory.

U.S. policy against ISIS suffers from three fundamental flaws. First, the United States has adopted what deceptively appears to be a low-cost, low-risk approach, which depends on the YPG to fight ISIS. This near-exclusive reliance on Kurdish forces is insufficient if not dangerous: The United States gives arms and air support to a Kurdish-dominated ground coalition that many local Sunni Arabs hate as much as and sometimes more than they hate ISIS. Arabs who join this ISIS-focused, Kurdish-dominated coalition theoretically benefit from this support, but those who fight both the Syrian regime and ISIS on the main front lines of the civil war are marginalized. The United States has shown no appetite for a serious, decisive effort to support the anti-regime insurgency, forcing it to depend on the Kurds as the only ally against ISIS.

It is tempting to rely on a group that appears to share the United States’s immediate priorities, but this approach is problematic. There is deep historical animosity between Arabs and Kurds in Syria. The Kurdish fight against ISIS has allowed the YPG to assert control over Arab populations and subdue local tribal governance. American support has also emboldened the YPG to carve out a Kurdish enclave in northern Syria, including in Arab areas. This is alienating Sunni Arabs from the United States and making them even less likely to fight ISIS. Finally, a Kurd-centric strategy assumes Kurdish forces are willing to do the United States’s bidding against ISIS in its heartland in Arab areas, territories the YPG is uninterested in since it is focused on building its own Kurdish state and has no desire to govern largely Arab populations outside that area. In any case, a Kurdish push into Arab territory in ISIS-held Syria would provoke a local backlash, which might well take the form of support for ISIS.

Second, the United States has failed to align its priorities with the local Sunni Arab population in Syria, which constitutes the anti-regime insurgency’s base. ISIS cannot be defeated without its cooperation. It is the only group willing and able to take the fight to ISIS’s Arab heartland in Raqqa, Deir al-Zour, and elsewhere. Only Sunni Arabs would be accepted as new leaders by populations liberated from ISIS, especially since many are themselves local to these areas. The Sunni-led insurgency has fought ISIS and driven it from large portions of Syrian territory. Rebels continue to fight ISIS around Damascus and Aleppo, in southern Syria, and in other key areas.

However, the Sunnis are not going to abandon the front lines against the regime and focus exclusively on ISIS. Were they to do so, the regime would attack them anyway. The war on ISIS gets a great deal of international attention, but it is the regime of Bashar al-Assad that is responsible for nearly all casualties and destruction inflicted on the insurgency and its Sunni Arab base. The insurgency’s current priority is therefore fighting the regime until it accepts a political settlement or is destroyed (depending on the rebel group in question). Any strengthening of the insurgency is effectively a net gain in the war against ISIS.

A successful strategy should be founded on one key principle: broadening the base of local partners willing and able to fight, destroy, and replace ISIS. This must include the Sunni Arab population that makes up the majority of Syrians, populates ISIS territory, and can offer a nonsectarian counter-narrative to its extremism. This population can be won over only if the United States addresses the civil war that has consumed it. To that end, the United States should provide a substantial increase in ammunition, financing, artillery, fuel, and other resources to any insurgent group that accepts the broad principles outlined in the Geneva II communique, centered on a political transition based on the mutual consent of the Syrian parties involved. The covert military operations centered in Jordan and Turkey are a logical model for supplying and advising insurgent commanders in Syria.

Perhaps more importantly, the regime’s unrelenting bombing of opposition areas must at least be decreased. It is making it impossible for insurgents to consolidate gains, provide governance and normalcy, and draw recruits away from ISIS. This problem can be addressed through providing man-portable air defense systems to select rebel groups, with built-in countermeasures to disarm or destroy weapons that fall into the wrong hands. The United States can also deploy special operators within insurgent units that receive sensitive weaponry—how many would depend on the American appetite for risk and how many insurgents are deemed qualified to receive such weaponry. At the early stages, this would likely be low.

Alternatively, while the idea of imposing a no-fly zone has been complicated by the presence of Russian aircraft operating over Syria, one way to counter regime air power is by destroying a significant regime asset or position every time regime aircraft target certain zones, or by giving the insurgents the means to do so through more accurate long-range weapons and better intelligence-sharing, thereby radically reshaping the regime’s air-power calculus. Presently, its aircraft operate with impunity over opposition-held areas. Its strategy, and that of its Russian partners, has included large-scale targeting of densely populated areas. In addition to inflicting massive destruction on homes, schools, hospitals, and other targets, this air campaign is one reason why insurgent groups have failed to establish a sense of normalcy or governance in territories they capture.

The United States should also revisit its criteria for vetting rebel groups for U.S. material support or training against the regime. Thus far, few of the most effective fighting groups fall into the ideological spectrum that the United States finds acceptable. Ideally, the United States would partner only with those espousing a secular democratic ideology. But the fact is that much of the insurgency is Islamist (though this should not be confused with “jihadist”), and micromanaging Syria’s ideological landscape is not and should not be the aim of U.S. policy in Syria, which should be centered on the closely connected goals of ensuring a just settlement to the war and defeating ISIS. In pursuit of these goals, the United States should support any actor willing to fight ISIS, accept a pluralist Syria, and encourage accountable governance and the rule of law. This does rule out some considerably powerful insurgent groups such as the hard-line Ahrar al-Sham, but it would also expand the scope of beneficiaries of U.S. support substantially.

Finally, there is an important geopolitical problem limiting the success of the U.S. war on ISIS in Syria. While the United States has successfully recruited regional Sunni allies such as Turkey and Saudi Arabia into the anti-ISIS coalition, their participation has been unenthusiastic and they have certainly shown no appetite for risky ground operations against ISIS in Syria itself. They also seem to understand that there is no interest among the insurgency—which many of them support—for an ISIS-centric approach in Syria. Even Turkey, a victim of multiple ISIS terrorist attacks, is far more concerned with helping the insurgents and limiting Kurdish expansion in Syria. This geopolitical disconnect is a mirror image of the more local misalignment between U.S. and Syrian priorities. Were the United States’s regional partners to perceive a serious American commitment to a proxy effort against the regime, it is likely they would be far more cooperative against ISIS in Syria.

These steps—more support for a wider range of insurgents; countering regime air power; and accounting for the interests of regional allies—would enable the United States to defeat ISIS in Syria. Failing to undertake these steps merely traps the most powerful potential anti-ISIS coalition members between regime and jihadist violence, and alienates critical regional partners. Thus far, the United States has focused exclusively on fighting ISIS, thus ironically undermining that fight. The Syrian civil war cannot be ignored any longer. Cooperation with local and regional partners is not merely support against the regime. It is a critical component of winning the war against ISIS.