Since spring 2015, Turkey has suffered a wave of high-profile terror attacks linked to the self-proclaimed Islamic State and the Kurdistan Workers' Party (PKK). In response, Turkey deployed ground combat forces across the border into Syria, with the aim of pushing the Islamic State and Kurdish forces from a small self-declared "safe zone."
Turkey faces a complicated, interrelated conflict: its military operations in Syria are partly designed to counter the insurgency it faces within its borders. The linkages between the Syrian conflict and domestic Turkish security are driving internal political instability, and the outcome of the Syrian conflict will have repercussions for U.S.-Turkey relations and U.S. policy objectives in Syria.
Although some of the United States' and Turkey's objectives in northern Syria are complementary, others are contradictory. The various actors involved in the conflict are pursuing different interests and goals often at odds with those of the United States. Meanwhile, most armed groups are also targeting the Islamic State. Thus, a U.S. effort to address only one aspect of the conflict (e.g., arming Kurdish groups to fight the Islamic State) could undermine competing objectives in the region (e.g., maintaining a strong relationship with Ankara).
The United States needs to consider the effects of its intervention in northern Syria on Turkey, its North Atlantic Treaty Organization ally, and on terrorist groups it seeks to destroy, including the Islamic State and Hayat Tahrir al-Sham, an umbrella organization dominated by al-Qaeda elements. The same challenges that confronted the Barack Obama administration will persist during the Donald J. Trump administration. To address these systemic problems, the United States should reconcile the contradictory aspects of its relationship with Turkey, including considering whether it is possible to eradicate the Islamic State without also addressing the Kurdish-Turkish sub-conflict or whether U.S. forces should participate in a new front in the multisided civil conflict.