During an event marking the 71st anniversary of the South Korean Armed Forces, several F-15K fighter jets flew a patrol over the disputed islands of Dokdo (or Takeshima in Japan), causing an official protest from Japanese officials.

The patrol was announced by South Korean President Moon Jae-in in a speech to the military. “Just a moment ago, the F-15K, the most powerful fighter-bomber in Northeast Asia, has returned from completing a patrol mission over our land Dokdo … without any problems,” Moon is quoted by Reuters. Four fighter jets were involved, two of them flew over the islands.

Japan called in a South Korean military attaché stationed in the country and lodged a complaint, according to Korean news agency Yonhap.

But the South Korea Defense Ministry dismissed Japan’s claim. “Dokdo is an inherent part of our territory historically, geographically and internationally, Japan’s claim deserves no consideration,” the ministry said in a statement. “Our military will firmly respond to any attempt to undermine Dokdo’s sovereignty”.

A week ago, Japan’s annual defense review referred to the islands as “inherent parts of the territory of Japan”, sparking similar protests among South Korean officials. The report also downgraded Seoul’s ranking as an important security cooperation partner from second to four.

Dokdo is the name South Korea uses for Liancourt rocks, several islets in the East Sea over which the incident happened. Japan uses the name of Takeshima while naming the region the Sea of Japan. While South Korea has control over the islets where it has built several infrastructures and keeps a small police force, its sovereignty over them is disputed by Japan. North Korea also has a claim on the islets.

The celebration was also an occasion for the Republic of Korea Air Force (ROKAF) to showcase its newly acquired Lockheed Martin F-35A fighter jet. Four of the eight aircraft delivered this year were shown. Forty F-35As were ordered to replace the aging fleet of F-5 Tiger, for a contract valued at $6.5 billion. The ROKAF should receive them all by 2021.

Worsening relations between South Korea and Japan

Territorial claims are at the center of a bitter dispute between the two countries. On July 23, 2019, fighter jets of the South Korean Air Force fired several hundred warning shots at a Russian Beriev A-50 airborne early warning and control aircraft that was flying near Dokdo islands. The Japanese authorities, who also deployed fighter jets during the incident, filed two formal complaints. One was aimed at Russia for its incursion, and the second was against South Korea’s reaction. “In light of Japan’s stance regarding sovereignty over Takeshima, the South Korean military aircraft having carried out warning shots is totally unacceptable and extremely regrettable,” said the representative of the government, Yoshihide Suga at the time.

In January 2019, an incident near the Korean island of Jeju, 85 km south from the Korean peninsula, saw a Japanese patrol plane fly near a South Korean ship in what Seoul deemed “a clear provocation”. A month before, a Kawasaki P-1 maritime patrol plane of the Japanese Self Defense Force (JSDF) reported being locked by the fire control radar of the Korean destroyer “Gwanggaeto The Great”. A video of the incident was released publicly.