Korean Navy radar lock-on incident
Video footage from the Kawasaki P-1 maritime patrol aircraft, released by the Japanese Ministry of Defense
Date 20 December 2018 (2018-12-20) Location Sea of Japan Claimed by Japan: off the coast of the Noto Peninsula[1] Claimed by South Korea: 100km away from Northeast of the Liancourt Rocks[2] Status Ongoing dispute
Belligerents
South Korea	Japan
Units involved
Republic of Korea Navy Korea Coast Guard	Japan Maritime Self-Defense Force
Strength
1 destroyer 1 Large Coast Guard Vessel	1 maritime patrol aircraft

The Korean Navy radar lock-on incident is a naval incident between the Japan Maritime Self-Defense Force and Republic of Korea Navy, and the ensuing diplomatic dispute between Japan and South Korea.

The Government of Japan claimed that, on 20 December 2018, a Gwanggaeto the Great-class destroyer of the Republic of Korea Navy irradiated a Kawasaki P-1 maritime patrol aircraft of the Japan Maritime Self-Defense Force by pointing STIR-180, a type of fire-control radar at their aircraft in the Sea of Japan.

The Government of South Korea denied and refuted Japan's claims, stating that the Japan Maritime Self-Defense Force's maritime patrol aircraft threatened their naval ships by continuously flying at altitudes of 300 to 500 feet (90 to 150 m) above sea level while they were operating the humanitarian rescue of a distressed North Korean fishing boat.

• On 20 December, the Japanese Ministry of Defense claimed a Kawasaki P-1 maritime patrol aircraft from Fleet Air Wing 4 of the Japan Maritime Self-Defense Force (JMSDF) was irradiated several times for a few minutes by a destroyer of the Republic of Korea Navy with a fire-control radar. The incident occurred off the Noto Peninsula in international waters within Japan's exclusive economic zone, away from the disputed Liancourt Rocks. After receiving the radiation, the P-1 patrol aircraft tried repeatedly to contact the other party by radio to ascertain their intentions, but got no response from the South Korean naval ship.^[3]
• On 21 December, the Japanese Minister of Defense, Takeshi Iwaya, held a press conference to clarify the facts of the incident. While he told the reporters that the intention of the Korean side was not clearly understood, he criticized the incident as an extremely dangerous action.^[4][5]
• On 22 December, the Japanese Ministry of Defense conducted a careful and detailed analysis of the incident, and concluded that the irradiation was from the radar of a fire-control system, which is unsuitable for broad searches.^[6] Accordingly, the Ministry of Defense stated that irradiation with a fire-control radar was a very dangerous action that could lead to unexpected contingencies. Even though it had been searching for a ship in distress, it greatly endangered other ships and aircraft in the vicinity. The Code for Unplanned Encounters at Sea (CUES), which both Japan and South Korea have adopted, suggests avoiding any radar irradiation from a fire-control system to aim at ships and aircraft.^[6] For these reasons, Japan strongly requested South Korea prevent any recurrence of the incident.

The Republic of Korea Navy announced that they did not use the radar function of the fire-control system but an MW08 radar, with the optical camera function of the fire-control system called STIR-180 (similar to AN/SPG-55). They also claimed that there was no intent to aim it at the Japaneseaircraft.^[7][8]

• On 23 December, the Japanese Minister of Foreign Affairs, Tarō Kōno, withheld any direct criticism, and announced that he would like to ask the Government of South Korea to respond to the incident in order to prevent relations between Japan and South Korea deteriorating.
• On 24 December, the Director-General of the Asian and Oceanian Affairs Bureau of the Japanese Ministry of Foreign Affairs, Kenji Kanasugi, visited the South Korean Ministry of Foreign Affairs to express Japan's strong regret and make a request for the prevention of the recurrence of this kind of incident. The Government of South Korea continuously denied the usage of STIR-180 while admitting the usage of MW-08 for the rescue.^[9][10] After the statement of the Government of South Korea, Takeshi Iwaya pointed out at a press conference that the Government of South Korea had some misunderstanding about the incident, and published a statement by the Japanese Ministry of Defense that the maritime patrol aircraft had been repeatedly irradiated with electromagnetic waves characteristic of a fire-control system radar continuously for certain periods.^[11][12]
• On 26 December, a member of the South Korean Justice Party accused the Japanese Government, particularly the Liberal Democratic Party, of trying to antagonize South Korea by making up the allegation that the radar was pointed at the patrol plane.^[13]
• On 28 December, the Japanese Ministry of Defense released a video taken by the maritime patrol aircraft during the incident.^[14][3] The video shows that a crewmember asked the destroyer in English several times via three frequencies about the FC anntena directed at the P-1, but the destroyer stayed silent. The video also shows the gray destroyer sailing near a pair of rubber boats and a North Korean vessel.^[15]
• On 2 January 2019, the South Korean Ministry of National Defense released a statement demandimg an apology from Japan that the P-1 patrol aircraft was flying dangerously low over their naval destroyer.^[16]

• 2013 Chinese Navy radar lock-on incident [ja]