What's that drone flying in over the horizon? It's a scout from Islamic State

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. In the seven months of the Iraqi government's drive to recapture Mosul from the jihadists, small drones have become a signature tactic of the group: Their appearance on the horizon, loaded with a camera, signals that punishing mortar barrages will soon be on the way.