The stakes were raised in northern Syria when Turkish troops and allied forces pushed into the Kurdish-run enclave of Afrin, setting off fierce battles with US-backed forces. For Turkey, the mission is clear: take Afrin and its surroundings to strike a decisive blow against a group Ankara sees as linked to the Kurdistan Workers Party (PKK), which has fought an on-and-off insurgency against the Turkish state for several decades. However, things are more complicated than the official Turkish line admits. Whereas Ankara claims that the People’s Protection Units (YPG) are ‘terrorists’, threatening the Turkish state, the YPG has been one of the main allies in the battle against Islamic State (IS) militants in Syria. The group, as part of the Syrian Democratic Forces alliance it leads, retook the city of Raqqa from IS last year. Washington’s support for the group has been a controversial issue in Turkish-US relations for years.