Little Machines of War — Stephen Donald Huff

On the verge of a bloody and catastrophic defeat, a lone surviving robot tech risks life and limb to maneuver to the frontlines and activate an army of machines. Though these metallic monsters have failed in the past, this time their success would be utter and complete. Too complete, perhaps. These machines are harbingers of global apocalypse and genocide. Be careful what you wish for, because not all is fair in love and war.