In Baghuz, a single black flag flutters in a light afternoon breeze above wrecked vehicles and improvised tents – the last Islamic State banner flying over the last of its territory east of the Euphrates.

The final slice of the terror group’s "caliphate" is braced for a fresh assault from Western-backed forces, who relaunched their stalled offensive against Islamic State of Iraq and the Levant (Isil).

After years of hard fighting, the Syrian Democratic Forces (SDF), a Kurdish-led alliance, have boxed Isil into a tiny triangle of land next to the village of Baghuz, a rural settlement on the fertile banks of the Euphrates river.

But for the past week, the battle has been locked in a frustrating…