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.