Japan is considering expanding its Air Defense Identification Zone (ADIZ) to include Pacific islands, in light of China increasing military activity in the Pacific, the Asahi Shimbun reported on the 4th.

According to the report, the Ministry of Defense is considering incorporating the airspace over the Ogasawara Islands, Pacific islands south of Honshu, into the ADIZ.

An ADIZ is a boundary set unilaterally to enable early identification of aerial threats. It is distinct from sovereign airspace under international law. When aircraft deemed to pose a risk of intruding into its airspace enter the ADIZ, Japan responds by scrambling fighters, among other measures. The current Japanese ADIZ is based on what the U.S. military established in the 1950s, and at the time the airspace over the Ogasawara Islands was not included.

Asahi explained that “the intention is to strengthen the SDF surveillance posture in consideration of China becoming more active militarily in the Pacific.” However, the paper noted that including the airspace over the Ogasawara Islands in the ADIZ could heighten military tension with China.

The paper reported that when Japan in 2010 extended its ADIZ to the vicinity of Yonaguni Island in Okinawa Prefecture, an island near Taiwan, Taiwan expressed regret at the time. When China in 2013 designated the East China Sea, including the airspace over the Senkaku Islands (Chinese name Diaoyu Dao), as an ADIZ, the United States and Japan criticized the move.

Because the airspace over the Ogasawara Islands does not overlap with the ADIZ of other countries, the paper reported that there is optimism within the Ministry of Defense that “there is no need to take into account backlash from neighboring countries.” However, if scrambles by the SDF increase in response to movements by Chinese military aircraft after Japan sets the ADIZ, military tensions between the two countries could rise.

Expanding the ADIZ would require installing radar in the relevant area and changing fighter deployments, and Asahi reported that if the zone were to include the airspace over the Ogasawara Islands, some have pointed out that Japan would have to manage an excessively broad area. For the time being, there is a possibility that the government will use airborne early warning and control aircraft equipped with radar to fill the ‘surveillance gap’.