In November 2013, China established an Air Defense Identification Zone (ADIZ) in the East China Sea. As a result of this action, the South Korean public became alerted to two significant issues that had previously been unintentionally ignored.
The first was the recognition of the strategic value of a part of the East China Sea, called the South Sea (Namhae) by the public in South Korea. The second was the realization that certain areas of Japan’s ADIZ (JADIZ) should be adjusted in accordance with relevant changes in international law and in cooperation with South Korea.
In the past, the attention of the South Korean public has primarily been focused on sporadic but persistent military provocations by North Korea along the Northern Limit Line (NLL) in the West Sea (Seohae)/Yellow Sea. Disputes have also arisen between China and South Korea over the sea areas surrounding a submerged maritime feature called Ieodo by South Korea. Ieodo is located in South Korea’s part of the hypothetical equidistance line between both countries’ Exclusive Economic Zones. China and South Korea agreed that since the dispute is not about territorial sovereignty, but is related to maritime jurisdiction, it can be resolved through negotiations on maritime delimitation. This is due to the fact that Ieodo is a submerged rock and therefore not subject to a territorial sovereignty claim.
This agreed ROK-PRC understanding, however, seemed to have been challenged by the fact that the airspace over the sea areas was included in the China’s newly established ADIZ. International lawyers generally understood that the ADIZ had nothing to do with strengthening any claim over territorial sovereignty, but the word “defense” in the zone’s name was enough to provide confusion to the public and even experts on national security. Thus, the South Korean public concluded that the strategic value of the South Sea (Namhae) should be reassessed because of the perceived threat of China’s ADIZ to national defense and security.
In addition, the South Korean public realized that the airspace over the sea areas surrounding Ieodo was in Japan’s ADIZ and not in the South Korea’s ADIZ (KADIZ). This might have led to deepening public mistrust towards Japan. However, due to the explanations of the government and media, such problematic suspicions never materialized. The KADIZ and JADIZ were created before the adoption of the 1982 United Nations Convention on the Law of the Sea that established the 12 nautical mile territorial sea and 200 nautical mile Exclusive Economic Zone regime. At the time when both ADIZs were established, the waters surrounding Ieodo were not under national jurisdiction but considered part of the high seas.
Additional suspicions might have arisen in some parts of the 12 nautical mile territorial sea from South Korea’s islands, Hongdo and Marado. Since at the time of the establishments of the JADIZ and the KADIZ a state could delimit its territorial sea up to 3 nautical miles only, the parts of the territorial sea beyond the 3 nautical miles from the two islands to 12 nautical miles were not parts of the South Korea’s territorial sea, thereby being located in the Japan’s ADIZ. To rectify all these contradictions and controversies due to the change of relevant international law, South Korea inevitably extended its ADIZ, which entered into force on December 15, 2013. The current overlapping ADIZ zones between Japan and South Korea, therefore, should not be understood as a conflict, but a matter of adjustment, unlike the overlapping zones between China and South Korea.