Turkey's recent shelling of the Syrian Kurds once again highlighted the precarious situation the United States faces in Syria. On the one hand, it needs to placate Turkey while it continues to support its Syrian Kurdish People's Protection Units (YPG) rival. On the other, it needs to ensure the protection of the YPG from Turkey so that it continues to focus its efforts and resources on fighting the Islamic State (ISIS). 

After the Turkish military shelled the border regions of Kobane and Gire Spi (Tal Abyad) in late October the YPG, predictably, diverted their resources from the larger Syrian Democratic Forces (SDF) coalition's offensive against the remaining ISIS pockets in eastern Deir ez-Zor province in preparation for combating any additional Turkish aggression. 

This also happened in early 2018 during Turkey's two-month-long invasion of Afrin, which gave ISIS a brief, but much needed respite that it used to recruit new members and launch attacks. This time, however, the diversion proved very short-lived and the SDF/YPG promptly got back to fighting ISIS.

Unlike the case in Afrin, the US works closely with the YPG in northeast Syria and has a vested interest in ensuring Turkey does not launch a similar cross-border military campaign there, something that Turkey has recently threatened. Such an action would certainly jeopardize the ongoing U.S.-backed efforts to destroy heavily entrenched ISIS forces in the town of Hajin in Deir ez-Zor. That is why it promptly began military patrols along the Turkish border, on November 1, in a clear bid to deter any further destabilizing attacks. 

The Americans then stepped up their efforts to de-escalate the situation.

Less than a week after the US began patrolling south of the Turkish border the US State Department offered multi-million dollar bounties for information on the Kurdistan Workers' Party (PKK) leadership, an apparent attempt to appease Ankara and dissuade it from attacking the YPG. 

While Ankara welcomes the move in principle it remains suspicious of US motives. Turkish officials invariably argue that the bounties ring hollow so long as the US continues to work with the YPG, which Ankara views as indistinguishable from the PKK. 

US troops recently visited the Syrian Kurdish border with Turkey along with SDF commanders in order to reassure locals that they will protect them. 

Then, on November 21, US Secretary of Defense James Mattis announced that the United States is establishing "observation posts" along the Syrian border in a clear bid to prevent more clashes. 

"We are putting in observation posts in several locations up along the Syria border, northern Syria border, because we want to be the people who call the Turks and warn them if we see something coming out of an area that we're operating in," Mattis told reporters, stressing that this initiative will not require sending more US troops to Syria. 

"What this is designed to do is to make sure that the people we have fighting down in the [Euphrates River Valley] are not drawn off that fight, that we can crush what's left of the geographic caliphate," he elaborated, in a clear allusion to recent developments. 

The US Special Representative for Syria Engagement James Jeffrey acknowledged Turkey's objections to the US partnering up with the YPG and even described the group's political wing as "the Syrian offshoot of PKK." He nevertheless stressed that the US has "not designated it as a terrorist organization, which we did with the PKK."

Referring to Washington's ongoing balancing act between the two sides Jeffrey said that the US mission against ISIS "will be finished" inconclusively if Washington turns its back either "on the Turks, or on our allies in the northeast, which is the SDF."

Jeffrey also argued that the fact the US has only supplied the SDF/YPG with light weaponry demonstrates that it is not arming the group to an extent that would enable it to pose any serious threat to Turkey, which has a well-armed military and the second largest army in the NATO alliance.  

Mattis also, in another comment aimed at placating Ankara, stated last year that the US will even try to recover the weapons it has provided the YPG following ISIS's defeat. 

The US 2,000 troops currently in Syria is not a large enough force to effectively confront and destroy ISIS on its own. A sizable local partner force is essential for numerous reasons. Jeffrey has readily acknowledged that the US could not have attained the same results it has against ISIS in Syria without its ad-hoc alliance with the SDF/YPG. 

It's unclear how long the US can continue to sufficiently balance its relations between the Syrian Kurds and Turkey. In recent months, Washington has affirmed that it will retain an open-ended military presence in northeast Syria until ISIS is verifiably defeated and Iran-backed militia groups leave the country. 

US forces could be there for many more years to come. Recent events reinforce what has been clear for years now: that being that any successful long-term US presence in Syria will certainly necessitate the establishment of a more complex and sustainable formula that will enable the Syrian Kurds and Turkey to coexist.