This weekend as many as 2,500 residents of Mosul escaped from the western half of a city that has been under the yoke of so-called Islamic State (IS) for almost three years.

Aid agencies estimate that there are approximately 750,000 civilians trapped in western Mosul, unable or too frightened to leave despite the very real prospect of a prolonged, intense battle over the city between Iraqi government forces and IS fighters.

The assault on western Mosul has, thus far, been largely as expected – a much better equipped and better trained Iraqi army than the one humiliated by IS in 2014, methodically pushing towards the edge of the city thanks to overwhelming fire power and the cover of coalition air strikes.

For all their brutality and intolerance, IS fighters are nothing if not ingenious and in recent days they have been deploying a battle tactic almost unprecedented in modern urban warfare – the use of commercially available drones to drop bombs and grenades against civilian and military targets.

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