FORAGING in South Korea’s mountains may soon become more fruitful. Since a wild ginseng digger reported the wreckage of a small unmanned aerial vehicle (UAV) on April 3rd, the South’s ministry of defence has been ruminating on rewards for anyone who spots an enemy drone. The report followed the discovery of two other similar aircraft: on March 24th in Paju, a border city; and on March 31st on Baengnyeong island, near the disputed Northern Limit Line which demarcates the two Koreas’ maritime border. North Korean inscriptions on the planes’ batteries; an ongoing military investigation into their engines, fuel tanks and weight; and the sequence of the photographs found stored in one of the plane’s cameras suggest the drones were sent from North Korea. For others, their sky-blue camouflage paintwork, identical to that on larger drones paraded in the capital Pyongyang two years ago, was a giveaway. Though they look more like hobbyists’ miniatures than an army’s aerial spying devices, the South Korean government is taking the presumed illegal incursion into its airspace seriously. All three drones entered the country undetected by the South’s army; one flew 130km before crashing on the east coast over six months ago (but was only reported last week). Another took 193 photographs of secured areas including maritime facilities in the Yellow Sea and the Blue House, the presidential residence, before turning northwards.

Warmongers decry a Northern infiltration as grave as that of North Korean commandos sent, in 1968, to assassinate Park Chung-hee, a former strongman and father of the current president, Park Geun-hye (they got to within 100 metres of the Blue House). Ms Park blasted the army this week and demanded swift countermeasures. The small drones, roughly one-metre-long and two-metres-wide, and made of polycarbonate, can go undetected because of their size, speed, altitude and weight. They may be able to carry a few kilograms of explosives. Some say they could even enter South Korea, wreak havoc and leave unnoticed, dispersing, say, anthrax spores over a populated area or a military unit.

In days the South’s ministry of defence conjured up plans for GPS jamming devices, better heat detectors and more anti-aircraft guns along the border. According to Yonhap, South Korea’s news agency, the ministry has earmarked 200 billion won ($190m) to buy ten sophisticated low-altitude radars, capable of detecting tiny flying objects, from Israel. For good measure, on April 8th, the South paraded two of its own home-grown drones, which have infrared cameras and can hover for hours while watching North Korean troops on the border, for the first time. The ministry has already declared drone-based military campaigns “a new security threat”.

Some defence hands disagree. Lee Hee-woo, a former military pilot and president of the ILS Research Institute (which is supported by South Korea’s air force), based in Daejeon, says the government’s response is overblown. The resolution of the photographs found on the drones’ cameras is very low—“no better than Google Earth”. The images cannot be transmitted back to base in real-time (the North would have to wait for the return of the aircraft). To keep the plane off the South’s radar, it needs to be small and light—and few think the North has the know-how to miniaturise biochemical bombs, let alone nuclear ones. And as the drone flies according to GPS co-ordinates plugged into the device before take-off, the effectiveness of a strike would anyway be very limited.

The North has no satellite reconnaissance of the South; such aerial spying devices are one of the few ways it can get pictures. Even if the value of the drone is minimal from a military point of view, it helps to narrow the North’s intelligence gap, says Daniel Pinkston of the International Crisis Group, a think-tank. The images are more up-to-date than Google Earth, so more useful in the event of an operation. (If the drones were equipped with videos, the data could be used to select targets in other weapons, such as cruise missiles.) An overhead view adds to the North’s current intelligence, particularly in high-security areas, of which human sources on the ground may have only limited knowledge. Over time, it chips away at South Korea’s advantage in technical intelligence, much of which is derived from military satellite pictures of the North. As the North has found it more difficult to send old-fashioned spies to the South (chiefly due to cost and improved counter-espionage), it appears to be tinkering with a cheaper way to gather some form of intelligence. For the South, the mountainous border area will always be a challenge to vet thoroughly with radar.

The hullabaloo that the three tiny devices have caused in the South suggests the North will at least use them as a scare tactic, says Mr Lee. The gangster regime has also proven that it can get through the South’s air defence systems—achieving something of a military hat-trick since 2010. An opposition politician lambasted the army, under the current and former conservative governments, for having now failed to prevent an incursion in all three of its ambits: at sea (when the Cheonan warship was sunk in 2010); at land (when it shelled Yeongpyeong island, also in 2010); and now in the air. Despite a scramble to beef up its defence systems, such ammunition is likely to hurt Ms Park's party in the country’s upcoming local elections in June.

(Picture credit: AFP PHOTO/South Korean Defence Ministry)