With the Islamic State (IS) cornered in Raqqa, the US-led coalition is eagerly anticipating the fall of the self-proclaimed capital of the caliphate, but as IS land continues to shrink, it is replaced with new complexities in Syria.

The US has relied heavily on the Kurdish-dominated Syrian Democratic Forces (SDF), and with every weakening of IS comes a potential strengthening of the Kurdish hand, unsettling an already irate Turkey.

Turkey’s unease with the growing US-Kurdish alliance is not new, and increasing border skirmishes in recent weeks between the Kurdish People’s Protection Units (YPG) and Turkish forces suggests Turkish threats to invade Afrin is not mere saber-rattling.

The gradual defeat of IS leaves a political void. Even if local Arab forces govern non-Kurdish areas such as Raqqa, the security threat is unlikely to dissipate once IS gone, leaving a strong reliance on Kurdish firepower.

Lt. Gen. Stephen J. Townsend, the commander of the US-led coalition, acknowledged the importance of Kurdish fighters in helping Arab forces “buttress” and “do the hard stuff” in Raqqa.

According to Townsend, “Mosul and Raqqa are intermediate objectives on a path to a final victory,” and, especially in the case of Raqqa, this path introduces new regional flashpoints and jostling for influence.

The void left by IS is eyed by the US, with views of protecting its hard-fought gains in a costly three-year campaign against the militant group, but also by the Syrian regime backed by Russia and Iran.

With IS on the retreat, new dividing lines emerge between the multiple local and foreign forces that dot the Syrian landscape.

With a weakening Syrian-Iraqi border, Iran has a unique opportunity to create a land bridge from Tehran to the Mediterranean, covering Baghdad, Damascus, and Beirut, reinforcing its role as a dominant regional power.

The recent US willingness to confront any regime and Iranian-militia-spurred-aggression in these borders areas, as well as around the newly liberated areas taken from IS, highlights US concerns.

A de-facto border is being drawn along the Euphrates, both on the ground and in the sky.

As the fallout from the recent downing of a Syrian SU-22 jet by US forces proved, after it had fired on SDF positions, this new line brings new prospects of conflicts with Russia and regime forces.

The US has consistently stressed their ambitions in Syria lie solely on the defeat of IS. But, in a highly complex Syrian civil war, missions are difficult to isolate.

Whether it likes it or not, the US cannot risk abandoning its new zone of influence in Syria.

Washington has previously stressed their relationship with the SDF and YPG forces were tactical and short-term, partly to appease Turkey, but it can ill-afford a swift exit from Syrian plains.

IS did not grow to such a mighty force overnight; it happened under the passive eyes of the global powers, who finally acted when the group was firmly entrenched in Iraq and Syria and had committed grave atrocities.

Only after a relentless air campaign and significant efforts to train, equip, and fund local forces has the US-led coalition managed to deal a significant blow to IS.

Can the US afford to be a bystander once again in Syria, and risk any IS resurgence or indeed the next install of IS?

At the same time, can the US afford to allow a significant regional power shift by allowing unfettered Iranian access and Russian domination of Syria?

Recent statements by US Defense Secretary Jim Mattis suggest a US gearing for a long-term role in Syria and, indeed, a continued partnership with Kurdish forces that will hardly soothe anxieties in Ankara.

Mattis was much less decisive when asked about weapons recovery from the YPG forces than stated in the past.

“We’ll do what we can,” Mattis stated, who was keen to highlight that the fight against IS did not stop at Raqqa.

More importantly, Mattis expressed willingness to continue arms supplies to the Kurds as future missions dictated.

“When they don’t need certain things anymore, we’ll replace those with something they do need,” he explained.

Meanwhile, Turkish President Recep Tayyip Erdogan angrily insisted, “We will make the real owners of those weapons…pay for any bullet that will be fired to our country, for every drop of blood that will be shed.”

As the soft portioning of Syria becomes increasingly likely, each side is rushing to either protect or extend their de-facto borders.

Keen to counter Kurdish gains east of the Euphrates, Turkey is increasingly vociferous in its willingness to liberate Afrin, a Kurdish canton west of the Euphrates, already sandwiched by pro-Turkish Syrian rebels.

At the same time, the Kurds are seemingly undeterred, with threats of their own to clear the Jarablus corridor and realize their goal of connecting their cantons.

The post-IS battle lines threaten new rounds of violence, unless US, Russia, Turkey, and Iran can somehow strike a grand bargain.

In the case of Turkey, Ankara’s focus on curtailing Syrian Kurdish ambitions will inevitably result in trade-offs with Damascus and Moscow, solving one problem, but as always in Syria, adding much more.

First Published: Kurdistan 24