 Such an "attack drone" or "harassment UAV" now becomes difficult to logically distinguish from a cruise missile.The first operational battlefield UAV developed by the US military was for antisubmarine warfare (ASW).In the early 1960s, the US Navy obtained a small "Drone Anti-Submarine Helicopter" (DASH) Gyrodyne QH-50 that could fly off a frigate or destroyer to carry homing torpedoes or nuclear depth charges for attacks on enemy submarines that were out of range of the ship's other weapons.