The two current centers of resistance by the Islamic State’s caliphate are in the Iraqi city of Mosul and the Syrian city of Raqqa. Both cities have been heavily fortified by ISIS. Coalitions of opposition forces are advancing on both cities. Iraqi Kurds are important for the siege of Mosul and Syrian Kurds are important for the siege of Raqqa.
Of the two coalitions, the Syrian one is the more problematic. Raqqa holds particular importance as the capital city of the caliphate. President Obama has committed substantial military resources to the struggle: American planes are bombing; 400 Special Forces troops have been sent to Syria to serve as spotters for air strikes and to train local fighters; and Apache helicopter gunships have been used against Mosul’s defenses. However, in both countries, the brunt of the fighting has and will fall on local forces.
As an American military problem, this is simple enough. The Americans hope that the final attack on Raqqa can begin in February 2017. The core of the anti-ISIS force laying siege to Raqqa is Syrian Kurds. Around this core have been arrayed (or cajoled) loose groups of Syrian Arabs. The Syrian Arabs have much less experience with war than do the Kurds. This means that the Kurds will have to do most of the heavy lifting in the assault on Raqqa. The Defense Department believes that the Syrian Kurds need to be supplied with better weapons for an urban assault than those that have served them on open battlefields. These weapons would include rocket-propelled grenades, machine guns, and armored vehicles. Furthermore, the Defense Department has recommended that Apache gunships be used against Raqqa.
As an American diplomatic problem, this is less simple. Neighboring Turkey regards the Syrian Kurd political group (the Y.P.G.) as terrorists. If the Syrian Kurds succeed in carving out an autonomous Kurdish enclave in Syria they will have expanded the proto-state that is being created in neighboring Iraq. From this proto-state, at some point, the Syrian and Iraqi Kurds can begin to work to liberate the Turkish Kurds. Arming up the Syrian Kurds poses a future danger to Turkey. Turkey is a member of NATO and the United States is bound by treaty to defend it against outside attack.
The Turkish government has begun delaying approval of American air attacks launched from Incirlik air base and hampering the flow of supplies into the base. American diplomats suspect that Erdogan might respond to an increased armament for the Syrian Kurds by attacking Kurdish enclaved along the Syrian-Turkish border. This might compel the Kurds to divert forces from the attack on Raqqa. Worse still, Turkey’s authoritarian president, Recep Tayyip Erdogan, has begun to lean toward Russia. Already prone to blame the United States for many untoward events within Turkey and the region, Erdogan might contemplate disrupting the NATO alliance in the same fashion as did France’s Charles de Gaulle in the 1960s. A pessimist might see one possible outcome of arming the Kurds to be the weakening of NATO’s southeastern flank at a time when Vladimir Putin is on the watch for opportunities to extend Russian influence.
Grasping at straws, the Americans have contemplated promising the Turks that close monitoring of any weapons will prevent their use against Turkey. This is hardly credible given the failures to control weapons supplied to Syrian “moderate” forces. This leaves President Obama with no easy choices. Perhaps he’ll leave the decision to President Trump. The new president would be torn between the devil of improving relations with Russia and the deep blue sea of destroying ISIS.
 Michael Gordon and Eric Schmitt, “Obama’s Syrian Options: Arm Kurds or Let Trump Decide,” NYT, 18 January 2017.