The 2018 Japan–South Korea radar lock-on dispute is about an incident between a Japanese airplane and a South Korean warship. The aircraft was part of the Japan Maritime Self-Defense Force (JMSDF), while the vessel was part of the Republic of Korea Navy (ROKN). The event occurred on 20 December 2018, without the firing of any weapon, and was followed by a large diplomatic dispute between Japan and South Korea. In June 2024, both countries agreed on steps to prevent a recurrence, effectively dropping the issue without resolving the exact circumstances around the event itself.
Incident According to the Japanese government, a South Korean naval destroyer, ROKS Gwanggaeto the Great, directed its STIR-180 fire-control radar at a maritime patrol aircraft, Kawasaki P-1 belonging to the Fleet Air Wing 4 of JMSDF, which was conducting surveillance off the Noto Peninsula in the Sea of Japan on Thursday 20 December 2018 at around 3:00 p.m. (JST). According to Japan's Ministry of Defense (MOD), aiming the fire-control (FC) radar at a plane is a violation of the Code for Unplanned Encounters at Sea (CUES), as a lock with the FC radar is generally considered a hostile act one step before actual firing. The MOD further said the irradiation of the P-1 plane by the radar hit multiple times continuously over a certain period.
In contrast, the South Korean government denied Japan's claims, stating that it was not operating a STIR-180 radar (FC radar) but MW08 radar for the rescue when the Japanese airplane arrived at the site. The MW08 radar is a 3D radar for medium-range air and surface surveillance, target acquisition and tracking, capable of gun control against surface targets. MW08 can be used as an FC radar, but it is not connected with the fire-control system in the destroyer. In addition, South Korea claimed that the Japanese aircraft made a threatening "8-shape" flight continuously at a distance of and altitude of while the warship was participating in the rescue of a distressed North Korean fishing boat.
Timeline
2018 On 20 December, a fishing vessel sent out a distress signal. The South Korean coast guard and South Korean navy deployed rescue ships. The North Korean fishing boat was a small wooden boat that weighed less than 1 ton with four or five North Koreans at the time of the rescue. It was reported that one or two of the North Koreans had already died at the time of the rescue. The Korea Coast Guard and South Korean navy operated a radar to assist in the rescue. The Japanese Ministry of Defense (MOD) claimed a Kawasaki P-1 maritime patrol aircraft from Fleet Air Wing 4 of the JMSDF was irradiated several times for a few minutes by a destroyer of the Republic of Korea Navy with a FCR. The incident occurred off the Noto Peninsula within a joint fishing zone of the two countries, surrounded by 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. According to South Korea, the audio communication the Japanese P-1 patrol aircraft attempted to transmit contained severe static and thus the South Korean warship could not discern the message. 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 South Korean side was not clearly understood, he criticized the incident as an extremely dangerous action. On 22 December, the Japanese MOD conducted a careful and detailed analysis of the incident, and concluded that the irradiation was from STIR-180, which is unsuitable for broad searches. Accordingly, the MOD stated that irradiation with an FCR 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 an FCR to aim at ships and aircraft. For these reasons, Japan strongly requested South Korea prevent any recurrence of the incident. On 22 December, South Korean Ministry of National Defense (MND) announced that they did not use the FCR (STIR-180) but it was operating an MW08 radar with the surveillance and tracking functions. The South Korean MND also claimed that there was no intent to aim it at the Japanese aircraft. On 23 December, the South Korean MND argued that it had already explained its position to Japan and would strive harder to ensure that there would not be any "misunderstanding". On 23 December, the Japanese Minister of Foreign Affairs, Tarō Kōno, withheld any direct criticism, and announced that he would like to ask the South Korean government 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 South Korean government continuously denied the usage of STIR-180 while admitting the usage of MW08 for the rescue. After a statement of the South Korean government, Takeshi Iwaya pointed out at a press conference that the South Korean government had some misunderstandings about the incident, and published a statement by the Japanese MOD that the maritime patrol aircraft had been repeatedly irradiated with electromagnetic waves characteristic of a FCR continuously for certain periods. On 26 December, a member of the South Korean minor progressive Justice Party accused the Japanese government, particularly the ruling Liberal Democratic Party, of "trying to antagonize South Korea by making up the allegation that the radar was pointed at the patrol plane." On 27 December, Japan and South Korea held working-level teleconference over this issue between Mr. Hidehiro Ikematsu (Joint Staff Principal Councilor of the Japanese MOD) and Major General Kim Jeong-yoo (Operations Director of the South Korean JCS), etc. According to the informed sources of the South Korean military, Both JMSDF and ROKN proposed to bring data received by Japanese aircraft and information on radar equipped by South Korean destroyers, but they failed to meet an agreement due to security problem. According to the release of the South Korean MND, the defense authorities of the two nations "exchanged opinions regarding the truth and technical analysis to remove misunderstandings.", and agreed "to continue consultations on the matter. In case the two sides fail to settle the conflict through working-level talks, higher-level meetings could be held later" On 28 December, the Japanese MOD released a video taken by the maritime patrol aircraft during the incident. The video shows that a crewmember asked the destroyer in English several times via three frequencies (international VHF [156.8 MHz] and emergency frequencies 121.5 MHz and 243 MHz) about the FC antenna 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. Sankei Shimbun reported that Japanese Prime Minister Abe had directed Japanese Defense Minister Takeshi Iwaya to release the video publicly, though the Defense Minister was reluctant to release the video, worrying about a possible backlash from South Korea. The South Korean MND expressed deep concerns and regrets over Japan's release of video footage related to an ongoing military radar spat just one day after two governments started a "working level conference" on 27 December, and accused Tokyo of releasing "inaccurate" facts. The South Korean MND argued that "The video material released by Japan contains only footage of the Japanese patrol plane circling above the surface of the sea and the (audio) conversation between the pilots and it cannot by common sense be regarded as objective evidence supporting the Japanese claims. There's no change to the fact that our military did not operate tracking radar on a Japanese patrol plane."
2019 On 2 January, the South Korean MND released a statement demanding an apology from Japan that the P-1 patrol aircraft was flying dangerously low over their naval destroyer. On 4 January, Japanese Foreign Minister Taro Kono and South Korean Foreign Minister Kang Kyung-wha agreed over a phone conference to resolve the issue through "consultations between their military authorities". The South Korean MND released a video criticizing Japan for the low flying altitude of the maritime patrol aircraft. The video also claimed that the South Korean destroyer did not illuminate any tracking radar. The video mainly consists of the materials released by the Japanese MOD a week before. On 8 January, Japanese Defense Minister Takeshi Iwaya repeatedly commented that Japan would be able to exchange radar wave records with the South Korean military to deepen discussion with South Korea. On 14 January, Japan and South Korea held a conference at Singapore. At this conference, some of misunderstandings were explained like the communication, later found that the communication personnel in the destroyer had misheard the radio communication. Both countries suggested to analyze recorded data together, but they did not reach an agreement on major issues: about the usage of the radar and the threatening flight. The radar problem couldn't be resolved; the dissatisfaction of Japanese side about the radar was that Japan was asked to present the record of the RWR record first, not exchanging the records of both countries at the same time to avoid forgery, and the discontent of Korean side was that the Japan will show only a part of the P-1's record, excluding received frequencies, while the South Korean side was asked to disclose entire radars' specification and frequencies of the destroyer. About the matter of the threatening flight, Japan claimed "the MSDF P-1 maintained (even at its closet flight) a sufficiently safe altitude (approx.150m) and distance (approx. 500m) from the ROK destroyer" and requested South Korea for the objective evidence to support their claim, but South Korea had failed to provide such evidence and had repeatedly responded “if the subject of the threat feels threatened, it is then a threat," while the South Korean MND claimed that "safe altitude (approx.150m) and distance (approx. 500m)" is based on ICAO applying to civil flight, not a flight made by a government. They also claimed that when flights with altitude and distance admitted by Japanese were made to Japanese ship, JMSDF would also protest. Although Japanese MOD replied that they would not protest against it, Japan did not acknowledge it as an official statement when South Korean representatives asked whether they can declare it internationally. Both Japan and South Korea promised to hold further negotiations.