2018 Japan–South Korea radar lock-on dispute

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2018 Japan–South Korea radar dispute: a short, easy-to-understand version

On 20 December 2018, off the Noto Peninsula in the Sea of Japan, a Japanese maritime patrol aircraft (Kawasaki P-1) and a South Korean destroyer, ROKS Gwanggaeto the Great, were involved in a tense incident. No weapons were fired, but the matter sparked a major diplomatic dispute between Tokyo and Seoul.

What each side says
- Japan’s claim: The South Korean destroyer aimed its fire-control radar (the STIR-180) at the P-1 aircraft, a move Japan described as a hostile act under the Code for Unplanned Encounters at Sea (CUES). Japan said the radar directed at the plane hit it multiple times over a period.
- South Korea’s claim: Seoul denied using the STIR-180 fire-control radar. Instead, South Korea said the destroyer was using its MW08 radar for rescue operations during a distress situation with a North Korean fishing boat nearby. They argued the P-1’s flight path was threatening, describing an “8-shape” maneuver at a low altitude and close distance, but insisted no FC radar was active on the destroyer.

What happened next
- No shots were fired, but the incident caused a strain in Japan–South Korea relations and drew international attention.
- Over the following years, both countries said they would work to prevent a recurrence and improve safety and communication at sea.

Recent developments
- 17 November 2022: South Korea stated it had not irradiated radar.
- 4 June 2023: During the Shangri-La Dialogue, Japanese and South Korean defense ministers agreed to accelerate working-level talks to prevent recurrence.
- 2 June 2024: The two ministers met again and agreed to normalize military relations, resume defense cooperation, and take concrete steps to prevent similar incidents. A joint document stressed complying with CUES, improving communications, and rebuilding trust, but it did not recount the exact events of the 2018 incident.

Background notes
- The MW08 radar used by the South Korean ship is capable of tracking targets and can be used for surface engagement, but it is not tied to the destroyer’s fire-control system. The STIR-180 radar is a dedicated fire-control system.
- Some observers argued about whether the actions constituted a real threat, while others emphasized no one was injured and no weapons were fired.
- In general, Japan, the U.S. military, and NATO follow ICAO-style guidelines to maintain a safe distance from vessels during normal operations, roughly around 150 meters.

Current status
- By 2024, both countries described the issue as an obstacle to security cooperation but agreed on steps to prevent recurrence and to keep open channels for defense dialogue. The detailed sequence of events from 2018 remains unresolved publicly.