The recent crash of a North Korean unmanned aerial vehicle in Paju north of Seoul has increased worries that the North habitually uses surveillance drones over South Korea. It has also raised suspicions that the North deployed UAVs when it shelled Yeonpyeong Island and sank the Navy corvette Cheonan in 2010.
At the time of the shelling, 122 mm North Korean multiple rocket launchers struck South Korean K-9 self-propelled howitzer positions with relative accuracy. One military source said, "There was even talk at the time that a North Korean spy stole classified information, but now it seems more likely that the North already knew the positions from surveillance photos taken by UAVs."
Yoon Yeon, a former commander of naval operations, said before North Korea torpedoed the Cheonan, North Korea probably tracked the ship's route on the West Sea by radar, and it's possible that it flew drones over the Cheonan afterward check the result of its attack.