On the Heng Chun peninsula, which juts out of Taiwan’s lower end into the Philippine Sea, the December sun is blazing. Hsu Keng-Jui has a half-smoked cigarette protruding from the corner of his mouth. He is a member of a volunteer network, the most of whom are also veterans, that keeps tabs on the Chinese ships and planes that are currently always present just beyond Taiwan’s borders. Mr. Hsu attaches a long radio antenna to a steel railing with plastic zip ties, takes a seat with his portable radios, and starts listening to the military channels. The Taiwan coastguard guiding maritime traffic is the only sound we initially hear, a gentle southern lilt. Then, a distinct tone and accent are heard over the loud