The self-proclaimed Islamic State is under pressure in Syria today. In the Aleppo area, its defenses have been pierced by a Syrian government offensive backed by the Russian Air Force. Although most of the Russian airstrikes have hit other Sunni rebel groups (regardless of what the pro-Kremlin propaganda claims), some attacks target the Islamic State as well. In the deserts east of Homs, Syrian President Bashar al-Assad’s Russian-backed government is trying to reverse recent losses to the jihadi group. Should his army manage to recapture Palmyra, which was lost in May, it would be a severe blow to the Islamic State.

But until now, the most significant recent victories against the Islamic State have taken place further east and have come at the hands of an American-backed, Kurdish-majority alliance known as the Syrian Democratic Forces, or SDF.

Diving Into the Kurdish Alphabet Soup

Created as recently as October, the SDF is a political umbrella designed to provide legal and political cover for American military support to the Kurdistan Workers’ Party, better known as PKK. A Kurdish leftist group locked in battle with the Turkish government, it was designated a “ foreign terrorist organization” by the U.S. government in 1997 and graduated to become a Specially Designated Global Terrorist Organization in 2001, largely due to Turkish pressure.

The PKK, operating in Syria through a front group known as the People’s Defense Units, or YPG (with an all-female version called the YPJ), has emerged as the country’s most potent anti-jihadi force. Having crushed the Islamic State in Kobane in February, Tal Abyad in June, Hasakah City in July, and now in al-Houl on the Iraqi border, the Kurds and their local allies are gearing up for further offensives on jihadi strongholds near Raqqa and south of Hasakah. The White House desperately wants to support them, seeing few other ways to pressure the Islamic State in Syria.

So, in order to avoid any legal or political blowback, U.S. officials now insist that they are not at all working with the-organization-that-must-not-be-named, but rather with the SDF, where the YPG is only one member among many. And the United States has avoided adding the YPG to any blacklists, even though any American official could (but won’t) tell you that it’s a PKK front.

In fact, Pentagon officials insist that they are arming non-Kurdish SDF members, namely a group called the “Syrian Arab Coalition” (SAC). This is an in-house term used by no one in Syria, but it seems to refer to a number of minor Syrian Sunni Arab groups that connected with U.S. military personnel in Erbil, Iraq, this summer. Since they are too weak to operate on their own, they have been shoved in under the SDF umbrella alongside the YPG and a few other factions, including a PKK-friendly Syriac Christian militia. The Pentagon is well aware that the non-Kurdish SDF members are mere auxiliaries of the YPG/PKK, but they hope that this will change over time

The verbal contortions can seem silly, because regardless of who signs off on the delivery, the American ammunition dumps in Kurdish-held areas of northeastern Syria will of course feed straight into the PKK’s war effort. (Also, Kurdish politics was not in a pressing need of more acronyms.) But some justification had to be contrived and, well, it works. Since virtually all American journalists and politicians agree that the Syrian Kurds should be armed and to hell with the law, a curious omertà has emerged, with neither the media, nor the courts, nor Congress seeking to pursue the matter. This ensures that Iran-Contra style unpleasantries can be avoided and, no less importantly, that the Islamic State is now being knocked around like an amateur boxer in northeastern Syria.

The al-Houl Offensive

There has been much talk of an SDF offensive toward Raqqa, the key administrative center of the Islamic State in Syria, but that seems to remain a work in progress. Instead, on October 31, the SDF launched a major campaign against the Islamic State south of Hasakah City. One group of fighters slid in behind Islamic State lines via the Iraqi border region and within two weeks, the jihadi defenses had cracked. On November 13, Islamic State fighters evacuated al-Houl and Kurdish fighters took control. Since then, the SDF has pushed on relentlessly, clearing the Sunni Arab countryside around al-Houl and south of Hasakah City.

Al-Houl itself is hardly an awe-inspiring catch: a run-down, dusty little Bedouin town that few had even heard of before it became a target of the recent offensive. But al-Houl’s significance is not due to its size, but rather to its location. It lies west of the Iraqi Sinjar Mountain, very close to the border and to the road connecting Raqqa with Mosul, the Islamic State’s de facto capital in northern Iraq. Holding it helps protect Hasakah’s southeastern flank and it will cement Kurdish dominance in and around Has ak ah City.

The Islamic State has made repeated attempts to capture Hasakah, a provincial capital that straddles the line between eastern Syria’s Kurdish and Arab majority areas. In June, a major assault was preceded by waves of suicide bombers and it took weeks for the YPG and pro-government forces to jointly push the Islamic State out of the city.

“The more territory that the SDF can capture, the safer are its core areas from terrorist attacks or conventional military advances,” says Carl Drott, a doctoral candidate at Oxford University who focuses on the Kurdish areas of Iraq and Syria and has traveled extensively in the region. “ These peripheral areas serve as a buffer zone. Although al-Houl is an Arab town, it therefore makes sense for Kurds to try to wrest it from Islamic State control.”

Hasakah Goes Qamishli

By enveloping Ha sak ah from the south, the Kurds have not only made the city safer from jihadist attacks, but they are also tilting the balance inside the city itself. Hasakah has long been divided between Assad’s Syrian government and the Kurds, but it may now come to resemble Qamishli, a city further north. Qamishli is controlled mainly by Kurdish forces and the yellow banners of the YPG flutter at checkpoints all around the city. But its Arab neighborhoods, as well as many government facilities, military bases, and the airport, have been left in Assad’s hands. The government can thus continue to function, including both the civilian bureaucracy and the police apparatus—as long as it does not trespass on the domains of the YPG. While the arrangement is dysfunctional in many ways, with local citizens struggling to navigate the politics of both parties, not to mention a ridiculous amount of rival checkpoints, it has preempted the violent and anarchic collapse seen elsewhere in Syria.

There have been repeated flare-ups between the two sides, driven by both political (mis)calculations and ethnic animosity, but they typically end in the same way: with the Kurds humiliating the government. In February this year, Syrian intelligence arrested a Swedish journalist and his Syrian-Kurdish fixer in Qamishli. At first, the Kurds tried to negotiate for their release, but when they learned that the government had secretly flown its prisoners out of the Kurdish region for interrogation in Damascus, the gloves came off: the YPG unceremoniously brushed the Syrian army aside and picked up two high-ranking police commanders as bargaining chips. The Damascus government gave in immediately, sent the two journalists back to Qamishli and released them into Kurdish custody.

A similar arrangement had been imposed in Hasakah, which has an Arab majority population. Slightly simplifying a complex and fluid situation, the northern Kurdish-majority areas were controlled by PKK loyalists, while the Arab neighborhoods and suburbs in the south have been patrolled by Assad’s Baath Party, the army, and pro-government tribal militias. State institutions have been left in place and have continued to serve the wider population, more or less equitably, on the understanding that some neighborhoods are now no-go zones for Baathists and nosy bureaucrats, while the PKK’s own courts and institutions creep into the city from the north.

Unlike in Qamishli, the two sides have been fairly evenly matched in Hasakah, leading to occasional turf wars over who should control which streets and public utilities. But after the army’s poor performance in the battles against the Islamic State this summer, and with most of the southern countryside in SDF/YPG hands after al-Houl, the balance of power is now likely to tilt in favor of the Kurds. Still, Kurdish hegemony in Hasakah will inevitably rest on a weaker foundation than in Qamishli, and require more concessions and/or more repression, due to the lack of a majority constituency and the city’s proximity to a hostile Arab hinterland. The ethnic resentment this could breed is not necessarily a point in favor of the SDF’s anti-Islamic State efforts, but there you go.

The Oil Factor

In addition to shoring up their hold on Hasakah, the capture of al-Houl and other rural areas south of the city will provide the Kurds with a staging ground for attacks into the Syrian oil region.

On November 16, the SDF seized the Tishrin Oil Field, which is located only a few kilometers west of al-Houl. Developed since 2008 by the Chinese oil giant Sinopec, Tishrin is not one of Syria's larger fields, according to David Butter, a Chatham House expert on Middle Eastern energy who recently published a detailed report on Syria’s economy, but it will add to Kurdish fortunes. “The field produced 10,000 to 15,000 barrels per day in 2011, out of a national total of 380,000 barrels per day,” Butter tells me. “By comparison, the largest field in Syria, Sweidiyeh, which is in northern Hasakah and already under effective Kurdish control, produced about 100,000 barrels per day.”

However, the al-Houl area has apparently emerged as one of several hubs in the Syrian-Iraqi border region’s profitable trade in crude oil and locally refined oil products. Like other groups before it, the Islamic State seems to have made plenty of money by sharing in private refining and production schemes, taxing traders, and selling “ permissions” and “ protection” to independent entrepreneurs. The British researcher Aymenn al-Tamimi has published documents allegedly from an Islamic State financial office in the Deir Ezzor province south of Hasakah, which indicate that oil and gas contributed 27.7 percent of Islamic State revenues in that area, with electricity adding another 3.9 percent, and 23.7 percent chalked up to taxes (possibly including the fuel trade and businesses related to it).

Controlling the flow of oil also grants them a good deal of political leverage, since civilian communities and armed groups alike will quickly become dependent on deliveries. Islamic State-permitted exports of oil into rebel and government held areas to the west has often come with strings attached, one example being a quid pro quo deal between rebels and the Islamic State to allow food transfers to eastern Syria in return for fuel to the west. Similar arrangements exist between the Syrian government and the Islamic State, and indeed among hostile actors all over the country, including the major rebel groups and the YPG. It is a common feature of Syria’s war economy and it has little to do with political allegiances, even though the Syrian opposition and pro-opposition governments, including the United States, persist in trying to portray the bartering between Assad and various jihadis as evidence of a sinister conspiracy.

While the Kurds can’t tap exactly the same markets as the Islamic State, the overlap will be significant and the more of the eastern oil trade that the SDF manages to wrest out of Islamic State hands, the more power the group can wield in both Syria and Iraq.

Sinjar and the Raqqa-Mosul Road

On the Iraqi side of the border, a parallel but larger Kurdish offensive has recaptured Sinjar City—where the jihadis’ began their genocidal campaign against the Yezidi minority in 2014—and severed the main road between Mosul and Raqqa, which passes just south of the Sinjar Mountain in Iraq and south of al-Houl in Syria. That campaign was spearheaded by Peshmerga forces loyal to the rival Kurdistan Democratic Party (KDP), which dominates much of northern Iraq, but pro-PKK fighters had long been at the Sinjar front and were part of the action. PKK loyalists now hold territory on both sides of the border, working anonymously under the SDF umbrella in Syria while the party cadre in Iraq has spread out among a bewildering variety of uncloseted PKK units and ostensibly autonomous Yezidi militias.

“Controlling al-Houl is not only important to protect the Syrian Kurdish areas but also to protect the Sinjar area,” notes Drott, who traveled with Peshmerga forces on the Sinjar front this summer. “ One of the reasons to take al-Houl was undoubtedly to provide security for the Sinjar area.”

Losing the road means that the Islamic State risks losing cohesion, as communication between its two most important cities is now much more difficult. Cutting the group’s territory into disconnected islands seems to be a highly prioritized goal of the U.S.-led international coalition, in the hope that local Islamic State factions will turn on each other, fall under the influence of their tribal constituencies, or sue for separate peace once central control weakens. (For the PKK, taking al-Houl has the added benefit of facilitating cross-border communication at a moment when their chief Kurdish rival, the Turkish-backed KDP, is seeking to reassert itself among the Yezidis of the Sinjar Mountain.)

The dual offensives in Sinjar and al-Houl have thus reinforced each other. But while the Sinjar campaign has now reached the desert’s edge and is unlikely to go much further, there is potential for expansion south of al-Houl and Hasakah in Syria—if the SDF manages to broaden its base beyond the Kurdish community.

Into the Arab Tribal Region?

Should the Kurds and their allies manage to push deeper south into Islamic State territory, rolling down the Khabour river to the city of Sheddadi, they could do significant damage to the Islamic State “caliphate” in eastern Syria. Seizing Sheddadi would be a powerful symbolic setback likely to undermine faith in the Islamic State among local Arab tribes, and it would also disrupt the jihadis’ access to more trade routes and oil fields.

But it would be a hard slog. The river bank is dotted with little towns and villages that are virtually all Sunni Arab. Despite the best efforts of Kurdish and American spin doctors to present the advancing forces as a multiethnic army of no particular allegiance, except to liberty and the pursuit of happiness, the locals know perfectly well that “SDF” is just how people in Washington pronounce “ PKK.” And for all its military prowess, a group of American and Russian-backed Kurdish socialists might not be the ideal agent of change in the Islamist-ruled Arab Bedouin backwaters of eastern Syria.

In fairness, it should be said that the PKK and its various offshoots have come a long way from the narrowly Kurdish ethno-nationalism and communism that they started out with in the 1970s. They now promote an explicitly multicultural and anarchist-inspired ideology that seems very well suited to blurring ethno-sectarian differences—in theory, at least. But the PKK’s deeply entrenched authoritarianism makes it unlikely that it would long endure the kind of power-sharing arrangements that could appease suspicious locals and rope in opportunistic warlords, or that it would allow any independent ally to grow too strong or too popular. And this is why it is difficult, albeit not impossible, to imagine the SDF ever winning the level of Sunni Arab support it needs to operate effectively in the tribal region.

There’s also the question of how far the Kurds themselves want to go. They have every reason to clip the wings of the Islamic State in the Hasakah area, where aggressive forward action serves their defensive purposes. They are no less interested in securing extra oil wells to fuel their autonomy project. But at the end of the day, the PKK leaders are far more interested in the Kurdish parts of Turkey, Iraq, and Iran than they are in the Arab parts of Syria—and they know a thing or two about the risks associated with ruling a hostile civilian population.

Even in a best case scenario, a Kurdish force moving deep into eastern Syria would be overstretched and dangerously dependent on continued American support. And since the U.S. government is evidently too politically inhibited to even remove the PKK from its own terrorism list, a full year after picking the group as its main ally in Syria, the Kurds are only prudent in assuming that such support will not last forever.

America Has Made Its Bet

And yet, this is a job that has no other takers. The Pentagon has been chastened by its failure to develop anti-Islamic State militias from within the mostly Sunni Islamist armed opposition in the Arab parts of Syria. Very few troops were trained, due to cumbersome vetting procedures demanded by Congress, and those who were quickly proved either incapable or unwilling to stand up to jihadi pressure. While the CIA continues to tinker unhappily with Arab groups in northwestern and southern Syria, the military’s anti-Islamic State mission has decided to stick with the Kurds for lack of better options.

The plan seems to be to use the SDF to gradually glue more Arab groups onto a Kurdish core force while also separately standing up a nucleus of Sunni Arab fighters who belong to eastern Syrian tribes. Realistically speaking, these groups won’t be strong enough to dispense with the Islamic State and establish sustainable local governance on their own, and for reasons enumerated above, there is a limit to how far south you can go with the Kurds. But reality has a way of adapting, one way or the other, if you fire enough bullets into it. Should this limited force of pro-PKK Kurds and their Arab auxiliaries manage to beat the Islamic State on its home turf and tip the scales in at least one part of eastern Syria, new opportunities might open up and new allies might report for duty, reversing some of the pro-Islamic State snowball effect seen in 2014.

Or not. It is a gamble and it remains to be seen how it will play out, but the Pentagon has now placed its chips and the ball is rolling.

In late October, U.S. President Barack Obama authorized an American special forces unit of “less than fifty” soldiers to move into Syria for a “ train, advise, and assist mission.” While this has been portrayed as putting American boots on the ground, it is probably more about having eyes on your allies. Fifty soldiers won’t make a dent in the frontline, but they could work just fine as liaisons, giving technical support, and monitoring airstrikes. What’s more, they can coordinate logistics to make sure that American supply packages get to the intended groups—namely, the Pentagon-vetted “ Syrian Arab Coalition” militias that the United States has sought to incubate in the warm and perhaps a little overly tight embrace of the YPG.

On November 26, a pro-Assad television station claimed that about fifty American soldiers had arrived in Kobane. Soon thereafter, a Hasakah activist group cited unspecified “Kurdish sources” as saying U.S. personnel were spotted alongside YPG troops inspecting a military airstrip in Rumeilan Pasha, an hour’s drive east of Qamishli, near the Iraqi-Kurdish border. It might be mere gossip, disinformation, or coincidence. But if you’re interested in the future of the struggle against the Islamic State, I suggest you start keeping a close eye on Syria’s Kurdish-Arab borderlands.