The Kurdistan Workers Party (PKK) operates under the names of the Democratic Union Party and the People’s Protection Units in Syria. The PKK is registered as a terrorist group by most western governments, the European Union and Turkey, where it originated as a separatist organization. Nonetheless, the YPG has been the partner of the United States-led coalition in Syria against the ISIS. The strengthening of the YPG/PKK and its political messaging has brought in a flow of western foreign fighters. Some of these fighters are now returning to their homelands with indications that they are bringing security problems with them.