The war in Syria is more straightforward today than it was two years ago. That may sound counterintuitive, but “Syria,” properly speaking, exists now only in name.

A near-genocidal policy undertaken by the President Bashar Assad in Damascus has been followed by contradictory foreign interventions by Russia, Iran, Turkey and the United States, each of which has established its own zone of influence in the war-ravaged country. The resulting balkanization, a cauldron of endless conflict, has led to the worst humanitarian catastrophe of the 21st century; the deaths of 500,000, the wounding of more than 1,000,000, and the external or internal displacement of 11,000,000—roughly half the Syrian population.

There exists, however, a narrow window of opportunity for an incoming U.S. administration to achieve minimally defined objectives: defeating the so-called Islamic State, or ISIS, guaranteeing that it cannot come back, and making sure that its main rival, al Qaeda, cannot exploit the power vacuum that will come with the collapse of the caliphate.

Based on months of interviews with Syrian opposition figures, ISIS defectors, Sunni Arab tribesmen, U.S. military sources, and intelligence officials, we believe it necessary, as part of this plan, to keep small but effective U.S. garrisons indefinitely in eastern and northeastern Syria and western Iraq.

This is not as radical as it might appear. According to our U.S. military and intelligence sources, four installations already are being used by the anti-ISIS coalition, either openly or semi-covertly.

Developing these sites as solid anchors in the region will give the U.S. a badly needed intelligence-gathering capability in the Jazira, or Upper Mesopotamia, encompassing the arid plain that stretches across northwestern Iraq, northeastern Syria and southeastern Turkey.

In this century, the Jazira has been an incubator and a hideout for the transnational menace that, under a succession of names, including al Qaeda in Iraq, the Islamic State of Iraq and Sham (ISIS), and the Islamic State full stop, has bedeviled U.S. national security for over a decade.

The Jazira battlefield is complex, but not incomprehensible. Again, the core American objective is to crush ISIS, then to protect the local forces who carried out this campaign with U.S. backing, giving them enough security to allow them to rebuild their lives in their part of the Jazira.

The Assad regime has vowed to reconquer “all of Syria,” but once it feels secure in its own enclave, it is unlikely to expend the resources needed to do that, and its Russian and Iranian allies will have no particular interest in pursuing such a campaign.

Keeping contingents of U.S. forces in the region, meanwhile, will provide a credible deterrent helping to defend trusted and capable anti-ISIS fighters and deterring the Assad regime from any effort at reconquest.

Capitulating in the face of an Assad offensive to retake territories that he did nothing to help liberate from ISIS would, we believe, catalyze more terrorism and squander the hard-won gains of the last two and half years.

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What we are proposing does not in any way resemble an Iraq-style occupation; nor would it require a massive new commitment of American hard power.

It certainly would not approach the notion of “nation-building” long reviled by Donald Trump. Rather, it would expand upon battlefield victories already racked up in Operation Inherent Resolve, as the U.S.-led coalition against ISIS is formally known, and solidify them so that what happened in Iraq following the categorical U.S. military withdrawal in 2011 cannot be replicated in two nation-states.

Contrary to the conventional wisdom, such a counterterrorism-plus strategy would actually be well timed, owing to Syria’s fractured battlefield landscape. Broadly speaking, Syria can now be divided into distinct quadrants.

The South: In the province of Deraa, where the 2011 uprising against Assad began, the front between the regime and rebels is now relatively quiet. Syria’s neighbors, namely Israel and Jordan, have an interest in keeping this territory clear of both al Qaeda and ISIS. (Witness the Israel Defense Forces’ rapid annihilation of a ground of ISIS-linked jihadists who penetrated the Israeli-occupied Golan Heights last week.) Regional backers of the opposition that work closely with Jordan—principally Saudi Arabia and the United Arab Emirates—share a similar goal. All are committed to preventing extremists from holding sway in the south.

The West: The second quadrant runs along the eastern side of Syria, skirting the Lebanese border, up from Deraa to Damascus to northern Latakia and West Aleppo.

The Provinces of Idlib and Aleppo: Northwestern Syria is the scene of fiefdoms ruled by Islamists, nationalists, or jihadists. The CIA-backed Free Syrian Army factions there has been specially targeted for annihilation by the Damascus regime and Russia, and otherwise left too weak to pose a serious challenge to their opponents. The al Qaeda franchise Jabhat Fateh al-Sham—formerly Jabhat al-Nusra—has been busy building infrastructure and cultivating loyalists, particularly as ISIS is squeezed elsewhere. East Aleppo is being retaken acre by acre by the regime through a vicious Russian-led ++starve-or-surrender campaign++ backed up by extensive bombing. Whatever remains of the mainstream armed opposition is weakened, radicalized or cornered.

The main factor enabling the preeminence of Islamists in the northwestern corner of Syria is Turkey, America’s NATO ally. Nowhere in the country has Ahrar al-Sham, for example, managed to dominate more than in the areas close to the Turkish frontier. Ankara has provided Ahrar with immense financial, logistical and tactical help to ensure it stays strong and acts as a bulwark against the Syrian regime. Ahrar has even consented to Turkey’s intervention in Aleppo province, but that’s more to forestall Kurdish expansionism than it is to flush out ISIS.

Eastern Syria, the heart of the Jazira, is where the United States has been leading coalition forces in a very targeted, very brutal war against ISIS.

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The Trump administration should approach the Syrian conflict from this compartmentalized outlook. The solutions offered by analysts today to resolve the war ignore the unique conditions in different parts of an atomized country, treating the Syria of 2016 as though it were still the Syria of 2012. What works for the east does not work for the northwest; what works for the south doesn’t work for the regime-fortified center and the coast.

The U.S. should view southern and eastern Syria a terrain essential to its strategy for fighting extremism not only in Syria but in Iraq, for protecting two of its most important regional allies, Jordan and Israel.

The focus in the eastern and southern quadrants should be on working with locally accepted government, relying on the provincial council models that have arisen in the last five years and which the “Friends of Syria” bloc has been funding as transitional administrations.

The U.S.-led coalition, already has carved out parts of Syria—roughly 40 to 50 percent of the country’s geography, by our calculation—where the Assad regime and its Iranian- or Russian-built proxies cannot easily maneuver.

In the ISIS “briar patch”—roughly 40 to 50 percent of Syria’s geography, by our calculation—the Assad regime still holds strategic districts in the city of Deir Ezzor and a key airport.

The U.S. and its Western allies have the ability, by dint of their current presence, to dictate how much of this province, along with all of Raqqa, should be governed once the ISIS “caliph,” Abu Bakr al-Baghdadi, and his henchmen are dispatched or dispersed.

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A Jazira Strategy for establishing an American security protectorate would require the requisitioning of American forward operating bases from which opportunistic Joint Special Operations Command missions can be launched in partnership with trusted local actors trained as counterinsurgents.

Not only will this ensure the continued presence of American intelligence gatherers along the same longitudes where that intelligence matters most, it will also give the jihadists’ bellwether constituency—Sunni Arabs—a strong psychological incentive to work indefinitely with the U.S.

But what of Iraq? The vast parts of it that fall on the “Jazira: map have been the scene of savage conflict at least since the U.S. led invasion in 2003.

The Syria-Iraq borderland, particularly, has been a sieve; the transit corridor for countless “rat-lines” of jihadists moving back and forth.

It was this infamous gateway, from Hasakah to Ninewah and Raqqa/Deir Ezzor to Anbar, that let ISIS storm into Iraq in the summer of 2014, occupying roughly a third of a country which the United States spent trillions of dollars attempting to build into a functioning post-Saddam-Hussein democracy.

Instead, Iraq now appears increasingly beholden to Iran, whose operatives are at least as heavily involved in the ongoing war against ISIS as is the Pentagon.

Without eyes and ears on the ground in a country in which the U.S. military has been invested now for 13 years, American interests will be wholly at the mercy of Iran’s Revolutionary Guard Corps-Quds Force commander by Maj. Gen. Qassem Soleimani and his deputies.

In fact, a limited Jazira strategy was tried in 2008, when the U.S. still maintained bases along the Iraqi side of the Euphrates River Valley. Known as “Operation Defeat Al Qaeda in the North,” or OPDAN, the key element was shifting the U.S. Marines northward up from the Euphrates (which, by 2008, had been almost completely pacified) into the Jazira, so that their battle space extended all the way north to the Iraqi towns of Sinjar, Ba’aj, and Tel Afar, all in Ninewah province. The U.S. Army units were thereby able to move in the Tigris River Valley and focus on Mosul without having to worry about the border zone in 2008-2009—until the Marines left in the 2010.

The U.S. military categorically withdrew from Iraq three years later, rendering OPDAN a fleeting success.

The lesson to be learned there is that without a permanent surveillance and interdiction mechanism for the border, there is every likelihood that ISIS in its present form or some new incarnation, will be back to haunt us once the current war is “over.”

Over the last few years we have spoken with numerous tribal leaders in both Syria and Iraq, who have told us that the prevailing fear among Sunnis is that the U.S. will once again abandon the struggle against jihadism once ISIS is routed. This, more than anything, has made local inhabitants reluctant to resist the jihadists and to join in the U.S. backed effort to fight them.

According to Michael Pregent, a retired Army intelligence officer who served in Iraq, “trust is based on frequency and proximity. Asking Sunnis to do difficult things while stating U.S. support is temporary results in lasting instability. Permanent basing is required to build trust with the very Sunnis needed to defeat ISIS and reject future versions of the terrorist army.”

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The Pentagon has already stationed soldiers in at least four bases in the Jazira area, two without the permission of Syria’s central government; and two with the permission of Iraq.

In Syria, it has quietly commandeered the Rmeilan airfield in Hasakah province, doubling the length of a former crop-duster runway to accommodate C-130 military transport planes used to move materiel and men who are allied with the overwhelmingly Kurdish Syrian Democratic Forces.

As has been reported, U.S. (and British) Special Operations Forces have also trained up Syrian Arab anti-ISIS fighters at al-Tanf in southeastern Syria

In Iraq, U.S. “trainers” are currently stationed, with Baghdad’s consent, at the Q-West airfield in Qayyarah, a town about 16 kilometers west of the Tigris River which was recaptured from ISIS in July of this year.

Americans also are operating out of al Asad airbase in Anbar province, which is capacious and well equipped enough to have received Air Force One in 2007.

Given the indispensable role of U.S. air power and U.S.-built Iraqi military divisions in reclaiming most of ISIS-held Iraq since 2014, there is a chance that a new administration could negotiate a U.S. lease for these two installations with the Abadi government.

Gen. James Mattis, named by Donald Trump as the new U.S. secretary of defense, supported an enduring U.S. military presence in Iraq when he served in the Obama administration and, privately, we are told, endorses the idea now. As Trump’s defense secretary—and a Marine general still greatly respected in Baghdad—he should be in a position to negotiate such a deal now.

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What of the Kurds? They want their own autonomous regions—indeed, what the want is their own country. But Turkey is determined to prevent that from happening, and meanwhile the Assad regime has played with and against Kurdish factions at its convenience.

So the American involvement with Kurds as the lead fighters against ISIS in the regions near the Turkish border has been, to say the least, problematic.

In part, it relies on a diplomatic fiction distinguishing the anti-ISIS fighters of the Kurdish Peoples’ Protection Units (PYD) from the guerrillas of the PKK (Kurdish Workers’ Party) who are waging war on the government in Turkey. In fact, the PKK and PYD don't deny that they're in effect the same organization, and many of the U.S.-backed guerrillas fighting in Syria have also fought in Turkey.

The Americans’ base in Rmeilan is in the heart of the region the PYD calls Rojava. By building up the installation there, the U.S. would help to assure Kurdish autonomy, but also act as a limiting factor, helping to moderate the Kurdish ambitions.

A new base will also be necessary in the desert sandwiched between Iraq and Syria in the area of Al Qaim and al Bukamal, the towns on each side of the frontier.

In June, the U.S. launched a failed operation to expel ISIS from Al Bukamal using graduates of the New Syrian Army trained at al-Tanf. They failed, we are told by a high-ranking Jordanian government source, because after months of planning the operation, crucial air support was denied them at the last minute by a U.S. general. Also, the team used for the mission was far too small.

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ISIS often says its fallback strategy is one of inhiyaz, or temporary retreat, into the desert. Five years ago that maneuver allowed Al Qaeda in Iraq to regroup and plot its world-historical comeback. To preempt such a move requires building alliances and bases in the areas we propose.

“U.S. forces are trained and equipped to build such bases, or expand the existing ones,” says Lt. Col. Rick Francona, a former air attaché at the U.S. embassy in Damascus. “Without a long-term and committed American presence in this part of Syria, there is little chance that the situation will stabilize and remain so. The various factions operating there will revert to their inherent rivalries and outright hostilities.”

Such a presence could also be used to keep the peace between America’s feuding allies—a motley crew of factions with competing agendas ready to erupt if and when they defeat ISIS, or indeed before.

The Sunni Arab states of the Gulf would be encouraged to see a more robust American presence on the ground, somewhat assuaging their fears that Washington is selling out the region to Iran.

The U.S. must not wait on the timetable set by Assad, Vladimir Putin and Ayatollah Khamenei before it establishes its own facts on the ground, which its military dominance in the east allows.

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Some things are utterly predictable in the Middle East, and one is the claim that all strategy is tied to the exploitation of oil.

So be it.

The Jazira is the most oil-rich part of Syria, and what that means in practical terms is that the communities there will have an automatically enhanced political and economic stature relative to the rest of the country, giving the Syrian opposition a new bargaining chip at future parlays in Geneva.

Although Assad has repeatedly vowed to recapture every square inch of the country, he cannot feasibly do so with Turkish tanks rolling through the Aleppo countryside and U.S. Special Forces embedded with Kurdish and Arab militias in the north and south—at least not without risking open-ended war with the two biggest armies in NATO.

Deterrence, by way of fait accompli, has worked so far. Explicit deterrence will work still better.

The choice is not whether the U.S. stays in Syria or leaves, it is whether it stays or, eventually, is forced to come back.