Shortly after dawn on a southern Taiwanese beach, Robin Hsu¡¯s iPhone pings with the first radio message of the day from Taiwan¡¯s Air Force as it warns away Chinese aircraft.

¡°Attention!¡± a voice says on the radio, speaking in Mandarin to a Chinese military plane flying at an altitude of 3,500 meters. ¡°You have entered our southwestern air defense identification zone and are jeopardizing aviation safety. Turn around and leave immediately.¡±

Taiwan, which China claims as its own territory, has complained for years of repeated Chinese Air Force missions into its air defense identification zone (ADIZ), which is not territorial airspace but a broader area it monitors for threats.