Turkish President Recep Tayyip Erdogan says Ankara will launch an operation in northern Syria to remove the People's Protection Units, or YPG. The Kurdish militia is considered by Turkey as a terrorist group. Over the past 18 months, Erdogan has been repeatedly threatening to attack the U.S.-backed militia east of the Euphrates. The threats, however, were never carried out as the United States proposed forming a "safe zone" to stop any Turkish intervention.