US special forces are operating alongside Iraqi elite units and aligned with Kurdish peshmerga and Iraqi Shia militia backed by Iran. The decision now is about how to recapture Raqqa, the Isis stronghold in north-east Syria. That means deciding between two antagonistic US allies: Nato partner Turkey; and Syrian Kurdish militia known as the People’s Defence Units (YPG).
Not just the territorial defeat of Isis in its cross-border jihadi caliphate hangs on Mr Trump’s choice. The future of the Kurds, a stateless people spread over Syria and Iraq, Turkey and Iran, hangs in the balance too.