The silence was shredded by the rat-tat-tat eruptions of a single gun. More soldiers fired, their volleys coalescing into the grim music of war — a sustained snare drum roll soon interrupted by the bass thumps of the 50-caliber machine gun. All the barrels pointed at a speck tracing a line in the sky over west Mosul.

Their target was yet another drone dispatched by Islamic State.