Tensions are rising in northern Syria along the border with Turkey – an area that is already facing a grave humanitarian crisis following a decade-long civil war. Now Turkey, which has already carried out four on-ground offensives in Syria since 2016, has announced that it could launch another big military operation against the US-backed Syrian Democratic Forces (SDF). The SDF is largely made up of Kurdish People Protection Units, known as the YPG, and Turkey believes YPG to be behind a major bomb blast in Istanbul on November 13. The SDF and the YPG have denied any involvement. So, what is driving Turkey’s militaristic policy in Syria? Can Russia and the US, both of which have a military presence in Syria, stop Turkey from staging another offensive? What are the implications for the security of prisons in Syria where thousands of Islamic State fighters are locked up?