For months, even years, Turkish President Recep Tayyip Erdogan has threatened that Turkey’s armed forces and their Syrian rebel allies will launch a new attack on areas currently controlled by the Syrian Democratic Forces (SDF). The group is dominated by the Kurdish People’s Protection Units (YPG), the armed forces of the Democratic Union Party (PYD) Syrian branch of the Kurdistan Workers’ Party (PKK). The PKK is locked in an armed struggle with Turkey, and for Erdogan, the existence of any PKK enclave in Syria is a threat to Turkey and to his government. Similarly, within Turkey, domestic pol…